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methotrexate 2.5 mg tablet

Out of Stock Manufacturer QUALITEST/PAR P 67253032010
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Uses

Trophoblastic Neoplasms

Methotrexate is used in the treatment of trophoblastic neoplasms (choriocarcinoma, chorioadenoma destruens, and hydatidiform mole) in women except in those with impaired renal or hepatic function or who have failed to respond to previous therapy with methotrexate. These latter patients may be treated with dactinomycin. Methotrexate therapy is most effective in patients who have had the disease for only a short period prior to initiation of chemotherapy, who have low initial gonadotropin concentrations, and who do not have metastases. Complete remissions have been attained in about 75% of patients with metastases and in a higher percentage of patients without metastases. Methotrexate has also been used prophylactically against malignant trophoblastic disease in patients with hydatidiform mole.

In contrast to uterine choriocarcinoma, testicular choriocarcinomas are usually resistant to methotrexate alone. In patients with metastatic tumors of the testes, combination therapy utilizing methotrexate, dactinomycin, and chlorambucil has produced objective responses, as evidenced by decrease in size of metastases and tumor masses and/or lowered urinary chorionic gonadotropin concentrations in approximately 33-50% or more of patients treated. Following initial treatment, repeated courses of therapy at 1- to 3-month intervals for several years appear to be necessary in order to suppress tumor growth. In a few patients there has been an apparently permanent remission but control of tumor growth is often of only short duration.

Leukemias

Methotrexate also is used as a component of various chemotherapeutic regimens in the palliative treatment of acute leukemias. Present regimens are most effective in the treatment of acute lymphocytic (lymphoblastic) leukemia and have been reported to produce remissions in 90% of patients treated. Methotrexate has been used with corticosteroids to induce remissions, but the drug is now most frequently used alone or in combination with other antineoplastic agents for maintenance therapy following induction of remission with vincristine sulfate and prednisone. Combination chemotherapy usually produces longer remissions than use of a single drug. Methotrexate alone rarely is effective in the treatment of acute myeloblastic leukemia; remissions are short with relapses common and resistance develops rapidly. Methotrexate, however, may produce remissions in adults who have responded initially to mercaptopurine and who have become resistant to this drug. In addition, methotrexate has been used in combination regimens in induction of remissions of acute myeloblastic leukemia.

Leukemic infiltration into the meninges and CSF has been relieved temporarily by intrathecal administration of methotrexate. The drug may be effective in patients whose systemic disease has become resistant to methotrexate since leukemic cells in the CNS usually retain their original degree of sensitivity to methotrexate; however, poor responses generally occur in patients with initial methotrexate resistance. Focal leukemic involvement of the CNS may not respond to intrathecal methotrexate and usually responds best to radiation therapy. Methotrexate is also used prophylactically against meningeal leukemia.

Osteosarcoma

High-dose methotrexate, followed by rescue therapy with either leucovorin or levoleucovorin, is used in combination chemotherapy regimens as an adjunct to surgical resection or amputation of the primary tumor in patients with nonmetastatic osteosarcoma. These regimens appear to prolong the relapse-free survival in such patients. Methotrexate is designated an orphan drug by the US Food and Drug Administration (FDA) for use in osteogenic sarcoma.

Breast Cancer

Methotrexate has been used alone or, more commonly, in combination chemotherapy for the treatment of breast cancer.

Combination chemotherapy used as an adjunct to surgery has been shown to increase both disease-free (i.e., decreased recurrence) and overall survival in premenopausal and postmenopausal women with node-negative or -positive early (TNM stage I or II) breast cancer. Adjuvant combination chemotherapy in early breast cancer has produced overall reductions in the annual rates of recurrence and death of 28 and 16%, respectively, with overall 5-year disease-free survival rates of 58.8 versus 49.6% for patients receiving combination chemotherapy versus those who did not. Adjuvant combination chemotherapy that includes methotrexate, cyclophosphamide, and fluorouracil has been used most extensively and is considered a regimen of choice. Although adjuvant hormonal therapy with tamoxifen (with or without combination chemotherapy) generally is used for node-positive, estrogen-receptor-positive postmenopausal women, adjuvant combination chemotherapy (with or without tamoxifen) also can be used in such patients, but differences in toxicity profiles may influence the choice of regimen. For node-positive premenopausal women, adjuvant combination chemotherapy (with or without tamoxifen) generally is used. Adjuvant therapy with combination chemotherapy and/or tamoxifen has been used in women with node-negative disease.

Controversy currently exists regarding which patients with node-negative and estrogen-receptor-negative breast cancer are most likely to benefit from such adjuvant therapy following surgery , but such patients with poor prognosis are reasonable candidates for adjuvant chemotherapy with an effective regimen (e.g., 6-12 months of methotrexate, cyclophosphamide, and fluorouracil initiated within 6 weeks of surgery); other node-negative patients also may be suitable candidates, but toxicities, costs, and other quality-of-life considerations should be weighed in assessing potential benefit. All patients with node-negative breast cancer are at some risk of recurrence, and effective adjuvant combination chemotherapy can increase both disease-free and overall survival, albeit less markedly than in patients with node-positive disease.

In patients with node-positive early breast cancer (i.e., stage II), an effective regimen of adjuvant combination chemotherapy (e.g., methotrexate, cyclophosphamide, and fluorouracil; cyclophosphamide, doxorubicin, and fluorouracil; cyclophosphamide and doxorubicin with or without tamoxifen) is used to reduce the rate of recurrence and improve survival in both premenopausal and postmenopausal patients once treatment to control local disease (surgery, with or without radiation therapy) has been undertaken. These combinations have been tested and established as providing therapeutic benefit, and are superior to single-agent therapy with conventional agents; numerous other combination regimens providing apparently similar outcomes also have been used but are less common or have been studied less extensively. Although long-term (e.g., 6 months or longer) chemotherapy with adjuvant regimens is clinically superior to short-term (e.g., preoperative and perioperative) adjuvant regimens, clinical superiority between 6- versus 12-month regimens has not been demonstrated. There is some evidence that the addition of doxorubicin to a regimen of methotrexate, cyclophosphamide, and fluorouracil can improve outcome further in patients with more than 3 positive axillary lymph nodes, and that sequential (i.e., administering several courses of doxorubicin first) regimens are more effective than alternating regimens in such patients; in patients with fewer positive nodes, no additional benefit from doxorubicin has been demonstrated. The dose intensity of adjuvant combination chemotherapy also appears to be an important factor influencing clinical outcome in patients with early node-positive breast cancer, with response increasing with increasing dose intensity; therefore, arbitrary reductions in dose intensity should be avoided. In women with stage II disease and more than 10 positive lymph nodes, high-dose chemotherapy and autologous bone marrow transplant is an option currently being evaluated.

In stage III (locally advanced) breast cancer, combination chemotherapy (with or without hormonal therapy) is used sequentially following surgery and radiation therapy for operable disease and following biopsy and radiation therapy for inoperable disease; commonly employed effective regimens include methotrexate, cyclophosphamide, and fluorouracil; cyclophosphamide, doxorubicin, and fluorouracil; and methotrexate, cyclophosphamide, fluorouracil, and prednisone. These and other regimens also have been used in the treatment or more advanced (stage IV) and recurrent disease.

Lymphoma

Methotrexate may also be useful in the treatment of Burkitt's lymphoma, advanced stages (III and IV, Peters' Staging System) of lymphosarcoma, especially in children when used with other drugs, and in advanced cases of mycosis fungoides (cutaneous T-cell lymphoma). Although radiation therapy is generally used for treatment of localized histiocytic lymphoma, lymphosarcoma, and mycosis fungoides, chemotherapy may be useful in the treatment of generalized stages of these diseases. Hodgkin's disease responds poorly to methotrexate therapy.

Psoriasis

Methotrexate is used in carefully selected patients in the symptomatic control of severe, recalcitrant, disabling psoriasis that is not adequately responsive to other forms of therapy; however, the drug is not curative. Methotrexate should be used in the treatment of psoriasis only after the diagnosis has been definitely established, as by biopsy and/or after dermatologic consultation. Although methotrexate has been reported to produce beneficial effects in up to 75% of patients with psoriasis, there has been only one brief controlled study and the long-term effects of the drug and optimal dosage have not been established. Prior to initiation of methotrexate therapy, patients should be carefully screened to exclude pregnant women and patients with renal, hepatic or hematopoietic disease, or infections. The potential benefit to the patient must be carefully weighed against the possible risks involved and patients should be informed of potential toxicity.

Methotrexate has also been used topically in the treatment of psoriasis; however, results of one study indicated that the drug had little visible effect on the psoriatic lesions and another reported that the usefulness of topical methotrexate was limited by adverse effects on the surrounding skin.

Rheumatoid Arthritis

Methotrexate is used for the management of rheumatoid arthritis in adults whose symptoms progress despite an adequate regimen of nonsteroidal anti-inflammatory agents (NSAIAs). Methotrexate is one of several disease-modifying antirheumatic drugs (DMARDs) that can be used when DMARD therapy is appropriate.

Pharmacologic therapy for rheumatoid arthritis usually consists of combinations of nonsteroidal anti-inflammatory agents (NSAIAs), DMARDs, and/or corticosteroids. The ultimate goal in managing rheumatoid arthritis is to prevent or control joint damage, prevent loss of function, and decrease pain. Although NSAIAs may be useful for initial symptomatic treatment of rheumatoid arthritis, these drugs do not alter the course of the disease or prevent joint destruction. DMARDs have the potential to reduce or prevent joint damage, preserve joint integrity and function, and reduce total health care costs, and all patients with rheumatoid arthritis are candidates for DMARD therapy. DMARDs should be initiated early in the disease course and should not be delayed beyond 3 months in patients with active disease (i.e., ongoing joint pain, substantial morning stiffness, fatigue, active synovitis, persistent elevation of erythrocyte sedimentation rate [ESR] or C-reactive protein [CRP], radiographic evidence of joint damage) despite an adequate regimen of NSAIAs. DMARDs commonly used in the treatment of rheumatoid arthritis include methotrexate, etanercept, hydroxychloroquine, infliximab, leflunomide, and sulfasalazine. Less frequently used DMARDs include azathioprine, cyclosporine, minocycline, penicillamine, and/or oral or injectable gold compounds. The role of anakinra, a recombinant human interleukin-1 (IL-1) receptor antagonist, in the management of rheumatoid arthritis remains to be established.

While many factors influence the choice of a DMARD, methotrexate has substantially greater long-term efficacy than other DMARDs and is used as the initial or anchor DMARD in many patients with rheumatoid arthritis. Because residual inflammation generally persists in patients receiving maximum dosages of a single DMARD, many rheumatoid arthritis patients are candidates for combination therapy to achieve optimum control. Although the most effective combination regimen of DMARDs has not been determined, regimens that have been found efficacious in clinical studies include combinations of methotrexate and cyclosporine, etanercept, hydroxychloroquine, infliximab, leflunomide, or sulfasalazine.

Low-dose oral corticosteroids and local injection of corticosteroids are effective in relieving symptoms in patients with active rheumatoid arthritis. In addition, limited evidence indicates that low-dose corticosteroids slow the rate of joint damage.

Several international groups of rheumatologists have issued consensus reports that address the role of tumor necrosis factor (TNF) blocking agents (e.g., etanercept, infliximab) in the management of rheumatoid arthritis. These groups state that use of TNF blocking agents is most appropriate in patients with active disease (5 swollen joints and elevated acute-phase response [ESR of 28 mm/hour or greater, or CRP level of 2 mg/dL or greater]) despite adequate exposure to methotrexate or other effective DMARD. A course of methotrexate in a dosage of at least 20 mg weekly (or lower dosage if toxicity develops) for 3 months is considered an adequate course of DMARD therapy, and failure with such a course should prompt consideration of modification of the therapeutic regimen (e.g., initiation of a TNF blocking agent). Other factors to consider when deciding whether to use a TNF blocking agent in the treatment of rheumatoid arthritis are differences in the aggressiveness of the disease, extent of structural damage, effects of the disease on quality of life, and toxicity of previously used DMARDs.

Once therapy with a TNF blocking agent has been started, patients should be assessed for therapeutic response (e.g., a 20% reduction in swollen joint count with a 20% reduction in acute-phase response). While therapy should be continued indefinitely in those who have responded to therapy and are not experiencing substantial adverse effects, therapy with the TNF blocking agent should be discontinued in patients who have not responded after 12 weeks.

Administration of methotrexate alone is not a complete treatment for rheumatoid arthritis, and the drug should be used only as part of a comprehensive treatment program, including nondrug therapies such as rest and physical therapy. Most patients with active rheumatoid arthritis will show some benefit from methotrexate therapy, although improvement often plateaus during the first 6 months of therapy with the drug (occasionally being maintained for 2 years or longer) and may wane during continued use. There is no substantial evidence that methotrexate permanently arrests or reverses the underlying disease process, although the drug slows its progression in some patients. NSAIA and/or low-dose corticosteroid therapy may be continued when methotrexate therapy is initiated; however, the possible increased risk of toxicity with concomitant use of methotrexate and NSAIAs should be considered. (See Drug Interactions: Protein Bound Drugs and Weak Organic Acids, and also Nonsteroidal Anti-inflammatory Agents.) Depending on the patient's response to methotrexate, corticosteroid dosage may be gradually reduced. The manufacturer of methotrexate states that combined use of methotrexate and gold compounds, penicillamine, hydroxychloroquine, sulfasalazine, or other antirheumatic cytotoxic or immunosuppressive agents has not been adequately studied to date and may increase the risk of adverse effects.

Head and Neck Cancer

Methotrexate is used alone and in combination therapy for the palliative treatment of recurrent or metastatic head and neck carcinoma. When used alone, at a dosage of 40-60 mg/m once weekly, methotrexate produces an average objective response rate of 30%. Duration of response is short at an average of 4 months.

In a randomized study, patients with recurrent or metastatic squamous cell carcinoma of the head and neck who received cisplatin and fluorouracil, carboplatin and fluorouracil, or methotrexate alone had objective response rates of 32, 21, or 10%, respectively. Although the objective response rate achieved with cisplatin and fluorouracil was greater than that observed with methotrexate alone, combination chemotherapy was associated with increased toxicity and no difference in survival was observed. In patients with recurrent or metastatic head and neck cancer who cannot tolerate combination therapy with cisplatin and fluorouracil, weekly low-dose methotrexate may be used.

Methotrexate frequently is used in combination regimens with other antineoplastic agents (e.g., bleomycin, fluorouracil, vincristine). Combination therapy with cisplatin, methotrexate, bleomycin, and vincristine has been used for the treatment of recurrent or metastatic squamous cell carcinoma of the head and neck. Further study is needed to establish the comparative benefit of methotrexate-containing regimens in the treatment of advanced head and neck cancer.

Crohn's Disease

Methotrexate has been used for its anti-inflammatory effects in the management of Crohn's disease. Results of several open-label, and double-blind, placebo-controlled studies in adults indicate that use of methotrexate can result in clinical response (including clinical remission) in patients with chronically active Crohn's disease who have not responded to prior therapies (e.g., corticosteroids, other immunosuppressants), although efficacy of orally administered methotrexate has not been consistently reported in placebo-controlled clinical studies.

Safety and efficacy of parenteral methotrexate in the management of active Crohn's disease was evaluated in a double-blind placebo-controlled multicenter 16-week study that included 141 adults with chronically active Crohn's disease who had inadequate response to a corticosteroid (i.e. , prednisone). To be included in the study, patients had to have a chronically active disease unresponsive to a minimum of 3-months of therapy with prednisone (12.5 mg daily) with at least one attempt to discontinue the corticosteroid. At baseline, patients had a median Crohn's Disease Activity Index (CDAI) of 181-190. The CDAI score is based on subjective observations by the patient (e.g., the daily number of liquid or very soft stools, severity of abdominal pain, general well-being) and objective evidence (e.g., number of extraintestinal manifestations, presence of an abdominal mass, use or nonuse of antidiarrheal drugs, the hematocrit, body weight). Patients were randomized to receive IM methotrexate (94 patients; 25 mg once weekly) or placebo (47 patients). Patients continued to receive prednisone, which was tapered over 10 weeks (starting 2 weeks after randomization), unless their condition worsened; however, no other drugs used for management of Crohn's disease (e.g., oral or topical derivatives of 5-aminosalicylic acid, budesonide, other immunosuppressive agents, topical corticosteroids) were allowed. The primary outcome was clinical remission (defined as a CDAI index of 150 points or less and discontinuance of prednisone) at the end of the trial (16 weeks). Clinical remission at the end of the study was reported in 39 or 19% of patients receiving methotrexate or placebo, respectively. In addition, patients receiving methotrexate used less prednisone overall and had a lower mean average CDAI score than those receiving placebo (170 points for methotrexate versus 193 points for placebo). Many patients in this study who entered remission after 16-24 weeks of treatment with IM methotrexate (25 mg weekly) were enrolled in a new trial which evaluated the safety and efficacy of parenteral methotrexate for maintenance therapy of Crohn's disease. In this multicenter, double-blind, placebo-controlled trial, 76 patients with chronically active Crohn's disease in remission were randomized to receive 15 mg of IM methotrexate once weekly (40 patients) or placebo (36 patients) for 40 weeks; no other treatment for Crohn's disease was allowed. After 40 weeks, a greater proportion of patients receiving methotrexate were free of relapse (defined as an increase of baseline CDAI of 100 points or more, or the need to initiate therapy for active disease) than those receiving placebo (65% for methotrexate versus 39% for placebo); in addition, a smaller proportion of patients receiving methotrexate required prednisone therapy for relapse when compared with those receiving placebo (28% for methotrexate versus 58% for placebo).

Safety and efficacy of oral methotrexate in the management of chronically active Crohn's disease was evaluated in 2 other randomized double-blind, placebo-controlled trials in 59 corticosteroid-dependent adults. Patients received a weekly oral methotrexate dosage of 12.5 mg for 9 months in one trial and 15-22.5 mg for up to 1 year in the other. Efficacy (measured by reduction of dosage of corticosteroids, reduction in CDAI, or reduction in Harvey Bradshaw index) of oral methotrexate was similar to that of oral mercaptopurine (50 mg daily) in one of the studies and to placebo in both studies.

Some clinicians state that pediatric patients with corticosteroid-dependent or corticosteroid-resistant, moderately to severely active Crohn's disease who had an inadequate response to or were intolerant of azathioprine or mercaptopurine, may receive methotrexate (10-15 mg/m weekly) for the management of such disease.(See Cautions: Pediatric Precautions.)

Other Uses

Methotrexate is used in combination regimens with cisplatin and vinblastine, with or without doxorubicin, for the treatment of invasive and advanced bladder cancer. Because methotrexate is absorbed through the ileum, placement of a Foley catheter or frequent emptying of the reservoir is advised in patients with long ileal loops or internal reservoirs during administration of methotrexate-containing regimens for the treatment of advanced or metastatic bladder cancer. Because elimination of methotrexate may be impaired and risk of toxicity increased in patients with renal dysfunction, edema, pleural fluid collections, or ascites, use of leucovorin rescue or deletion of methotrexate is advised if methotrexate-containing regimens are being considered for the treatment of advanced or metastatic bladder cancer in such patients.

Methotrexate has been used in second-line therapy for the treatment of recurrent small cell lung cancer. Although methotrexate is labeled for use in the treatment of the squamous cell type of non-small cell lung cancer, other agents are preferred for the treatment of this neoplasm.

Methotrexate has been used in treating a variety of solid tumors. In some studies, the drug has been administered by intra-arterial infusion alone or in conjunction with IM leucovorin calcium in the palliative management of carcinomas capable of being infused via a single artery. Low-dose oral methotrexate has been used in patients with chronic progressive multiple sclerosis. Results of several clinical studies indicate that low-dose methotrexate (7.5 mg weekly for up to 2 years) reduces both disease activity (as assessed by magnetic resonance imaging [MRI]) and sustained progression of disability (as assessed by the Expanded Disability Status Scale, the Ambulation Index, and standardized tests of upper extremity function). Patients with secondary progressive multiple sclerosis benefited the most from methotrexate therapy.

Methotrexate has been used for its immunosuppressive and/or anti-inflammatory effects in the treatment of psoriatic arthritis, systemic lupus erythematosus, vasculitis, dermatomyositis, polymyositis,Wegener's granulomatosis, and a variety of dermatologic and chronic refractory ocular diseases. Controlled studies have shown that oral or parenteral methotrexate therapy is effective in the short-term management of psoriatic arthritis; however, because of its potential toxicities, methotrexate is generally used in the management of this condition only in patients whose disease is severe and/or unresponsive to conventional therapy.

Dosage and Administration

Reconstitution and Administration

Methotrexate is administered orally. Methotrexate sodium is administered by IM, IV, or intrathecal injection; the drug may also be administered intra-arterially.

Methotrexate sodium injection and powder for injection should be reconstituted according to the manufacturers' directions.

For the treatment of meningeal leukemia, methotrexate must be administered intrathecally since passage of the drug from the blood to CSF is minimal. Prior to intrathecal administration of methotrexate, a volume of CSF approximately equivalent to the volume of methotrexate solution to be injected (e.g., 5-15 mL) is usually removed. If a lumbar puncture is traumatic, methotrexate should not be administered intrathecally. Two days should elapse before again attempting the injection. Methotrexate should be injected intrathecally only if there is easy flow of blood-free spinal fluid. Some clinicians recommend that the entire volume of methotrexate injection be injected intrathecally in 15-30 seconds. Aspiration should not be performed. For intrathecal injection, preservative-free methotrexate solutions containing 1 mg/mL are used; solutions may be prepared using preservative-free 0.9% sodium chloride injection as a diluent. Methotrexate formulations or diluents containing preservatives must not be used for intrathecal administration or high-dose methotrexate therapy.

Methotrexate sodium solutions should be inspected visually for particulate matter and discoloration whenever solution and container permit.

Dosage

Methotrexate should only be used under the supervision of a clinician who is experienced in cancer chemotherapy and in the use of antimetabolites.(See Cautions: Precautions and Contraindications.) Dosage of methotrexate sodium is expressed in terms of methotrexate. Various dosage schedules for methotrexate therapy alone and in combination with other antineoplastic agents and/or radiation therapy have appeared in the literature; dosage, route of administration, and duration of therapy must be individualized according to the disease being treated, other therapy being employed, and the condition, response, and tolerance of the patient. In patients in whom discontinuance of methotrexate has been required, therapy should be reinstituted with caution, giving complete consideration to further need for the drug and the possibility of recurrence of toxicity. Clinicians should consult published protocols for additional dosages of methotrexate and other chemotherapeutic agents and the method and sequence of administration.

Trophoblastic Neoplasms

For the treatment of trophoblastic neoplasms, the usual dosage of methotrexate is 15-30 mg daily, administered orally or IM for 5 days. A repeat course may be given after a period of one or more weeks provided all signs of residual toxicity have disappeared. Three to five courses of therapy are usually employed. Therapy is usually evaluated by 24-hour quantitative analysis of urinary chorionic gonadotropin which should return to normal or less than 50 IU/24 hours, usually after the third or fourth course. Complete resolution of measurable lesions usually occurs 4-6 weeks later. One or two courses of methotrexate therapy are usually given after normalization of urinary chorionic gonadotropin hormone concentrations is achieved. In the treatment of trophoblastic disease in women, regimens alternating courses of methotrexate therapy and dactinomycin therapy or combining administration of methotrexate and mercaptopurine or methotrexate, dactinomycin, and chlorambucil have also been used. In the treatment of trophoblastic disease in women, 10-15 mg of methotrexate daily has also been administered via the hypogastric artery until toxicity or therapeutic response occurred. Combination chemotherapy with methotrexate, chlorambucil, and dactinomycin has been used in the treatment of metastatic testicular tumors in men.

Leukemia

Although methotrexate is not generally a drug of choice for induction of remission of lymphoblastic leukemia, oral methotrexate dosage of 3.3 mg/m daily and prednisone 60 mg/m daily for 4-6 weeks have been used. After a remission is attained, maintenance therapy with methotrexate is administered twice weekly, orally or by IM injection, for a total weekly dose of 30 mg/m. Administration of the drug in twice-weekly doses appears to be more effective than daily drug administration. Alternatively, 2.5 mg/kg has been administered IV every 14 days.

For the treatment of meningeal leukemia, an intrathecal methotrexate dosage of 12 mg/m or an empiric dose of 15 mg, administered at 2- to 5-day intervals until CSF cell counts return to normal, has been suggested; this is then followed by one additional dose of the drug. Alternatively, 12 mg/m has been administered once weekly for 2 weeks and then once monthly thereafter. For prophylaxis against meningeal leukemia, a methotrexate dose of 12 mg/m or 15 mg has been used; the intervals for administration differ from the regimen used in the treatment of meningeal leukemia, and specialized references and the medical literature should be consulted for specific recommendations. However, because the volume of CSF is related to age and not body surface area, dosage regimens based on body surface area may result in inadequate CSF concentrations in children and high, potentially neurotoxic CSF concentrations in adults; therefore, some clinicians recommend that intrathecal dosage be based on the patient's age. Clinical studies indicate that intrathecal methotrexate dosage regimens based on age may be more effective and less neurotoxic than dosage regimens based on body surface area. The suggested intrathecal doses based on age are 6 mg for children younger than 1 year of age, 8 mg for children 1 year of age, 10 mg for children 2 years of age, and 12 mg for children 3 years of age or older and for adults; geriatric patients may require reduced doses because of reduced CSF turnover and decreasing brain volume.Regardless of the method used to determine intrathecal methotrexate dosage, the dose should be carefully checked prior to administration to minimize the risk of inadvertent intrathecal overdosage. Because methotrexate appears in systemic circulation following intrathecal administration, systemic administration of the drug should be appropriately adjusted, reduced, or discontinued. Systemic administration of leucovorin calcium simultaneously with intrathecal methotrexate may prevent systemic toxicity without abolishing the activity of the antimetabolite in the CNS. The manufacturers state that focal leukemic involvement of the CNS may not respond to intrathecal methotrexate therapy and may be best treated with radiation therapy.

Osteosarcoma

The recommended initial dose for high-dose methotrexate treatment of nonmetastatic osteosarcoma is 12 g/m administered by IV infusion over 4 hours (followed by leucovorin or levoleucovorin rescue) on postoperative weeks 4, 5, 6, 7, 11, 12, 15, 16, 29, 30, 44, and 45, on a schedule in combination with other chemotherapy agents (e.g., doxorubicin, cisplatin, the combination of bleomycin, cyclophosphamide, and dactinomycin [BCD regimen]). If the initial dosage is not sufficient to produce peak serum methotrexate concentrations of 454 mcg/mL (1000 mcM [10 mol/L]) at the end of the infusion, the dose may be increased to 15 g/m in subsequent treatments.

Leucovorin and levoleucovorin are used as rescue therapy following a high-dose methotrexate regimen to prevent acute toxicity. Leucovorin is administered orally, IM, or by IV injection starting 24 hours after the beginning of the methotrexate infusion. If the patient experiences GI toxicity (e.g., nausea, vomiting), leucovorin should be administered parenterally. The usual dosage of leucovorin is 15 mg (approximately 10 mg/m) orally, IM, or by IV injection every 6 hours for a total of 60 hours or a total of 10 doses.

Levoleucovorin is administered as an IV infusion at a rate no faster than 160 mg of levoleucovorin per minute every 6 hours for a total of 60 hours or a total of 10 doses, starting 24 hours after the beginning of the methotrexate infusion.

Patients receiving high-dose methotrexate regimens must be well hydrated and carefully monitored.(See Cautions: Precautions and Contraindications.) For specific information on dosage modifications, cautions, and precautions associated with high-dose methotrexate therapy, the manufacturer's prescribing information should be consulted.

Breast Cancer

Various methotrexate-containing combination chemotherapy regimens have been used in the treatment of breast cancer, and published protocols should be consulted for dosages and the method and sequence of administration. The dose intensity of adjuvant combination chemotherapy appears to be an important factor influencing clinical outcome in patients with early node-positive breast cancer, with response increasing with increasing dose intensity; therefore, arbitrary reductions in dose intensity should be avoided.

One commonly employed regimen for the treatment of early breast cancer includes a methotrexate dosage of 40 mg/m (administered IV) on days 1 and 8 of each cycle combined with cyclophosphamide 100 mg/m on days 1 through 14 of each cycle and fluorouracil 600 mg/m on days 1 and 8 of each cycle. In patients older than 60 years of age, the initial methotrexate dosage was reduced to 30 mg/m and the initial fluorouracil dosage was reduced to 400 mg/m. Dosage also was reduced if myelosuppression developed. Cycles generally were repeated monthly (i.e., allowing a 2-week rest period between cycles) for a total of 6-12 cycles (i.e., 6-12 months of therapy). Clinical superiority between 6- versus 12-month regimens has not been demonstrated.

There is some evidence that the addition of doxorubicin to a regimen of cyclophosphamide, methotrexate, and fluorouracil can improve outcome further in patients with early breast cancer and more than 3 positive axillary lymph nodes, and that sequential (i.e., administering several courses of doxorubicin first) regimens are more effective than alternating regimens in such patients; in patients with fewer positive nodes, no additional benefit from doxorubicin has been demonstrated. In the sequential regimen, 4 doses of doxorubicin hydrochloride 75 mg/m were administered initially at 3-week intervals followed by 8 cycles of methotrexate 40 mg/m, cyclophosphamide 600 mg/m, and fluorouracil 600 mg/m at 3-week intervals for a total of approximately 9 months of therapy. If myelosuppression developed with this sequential regimen, the subsequent cycle generally was delayed rather than reducing dosage.

Burkitt's Lymphoma and Lymphosarcoma

The usual dosage of methotrexate for the treatment of stages I or II of Burkitt's lymphoma is 10-25 mg/day orally for 4-8 days. Methotrexate is commonly given concomitantly with other antineoplastic agents in the treatment of stage III Burkitt's lymphoma and lymphosarcomas. In all stages, several courses of drug therapy are usually administered interposed with 7- to 10-day rest periods. Stage III lymphosarcomas may respond to combined drug therapy with methotrexate given in doses of 0.625-2.5 mg/kg daily.

Mycosis Fungoides

Clinical response occurs in up to 50% of patients receiving single-agent therapy with methotrexate for mycosis fungoides (cutaneous T-cell lymphoma). In early stages of the disease, the usual dosage is 5-50 mg orally once weekly. The need for dosage reduction or discontinuance of therapy is determined by response to therapy and hematologic monitoring. Methotrexate also has been administered twice weekly in doses of 15-37.5 mg in patients with disease that has responded poorly to once-weekly dosing. In patients with advanced stages of mycosis fungoides, combination chemotherapy regimens that include IV methotrexate in higher doses followed by leucovorin rescue have been used.

Psoriasis

For the management of psoriasis, a single 5- to 10-mg dose of methotrexate should be given 1 week prior to initiation of methotrexate therapy to detect idiosyncratic reactions. Optimum dosage has not been established and dosage must be based on individual requirements and response. Dosage must be constantly supervised by a physician who is experienced in the use of antineoplastic agents.

There are 2 dosage schedules suggested by the manufacturers. To avoid potentially lethal overdosage, patients should be instructed carefully about their dosage regimen, paying particular attention to the frequency of administration.

The divided oral dosage schedule, which is based on cellular kinetic studies, consists of 2.5 mg of methotrexate administered orally at 12-hour intervals for 3 doses each week; in this regimen, dosage may be increased gradually by 2.5 mg/week, but weekly dosage should usually not exceed 25 mg and should not exceed 30 mg.

In the weekly single-dosage schedule, the manufacturers suggest that 10-25 mg may be administered orally, IM, or IV as a single dose once weekly. The usual oral dose in the weekly single-dosage schedule is 7.5-25 mg, with an occasional patient requiring up to 37.5 mg; dosage may be increased gradually by 2.5-5 mg/week. The usual IM or rapid IV dose in the weekly single-dosage schedule is 7.5-50 mg, with an occasional patient requiring up to 100 mg; dosage may be increased gradually. The manufacturers state that the oral, IM, or IV dose in the weekly single-dosage schedule should usually not exceed 50 mg.

In most patients, substantial improvement usually occurs within 4 weeks and optimum results occur in 2-3 months. Cessation of methotrexate usually results in a recurrence of symptoms in 2 weeks to 6 months. After optimal response is achieved, each schedule should be reduced to the lowest possible dose with the longest possible rest period. Conventional topical therapy should be resumed as soon as possible.

Psoriatic Arthritis

The optimum dosage of methotrexate in the management of psoriatic arthritis has not been clearly established, although oral and parenteral dosage regimens similar to those used in the management of psoriasis have been employed. Clinicians should consult specialized references for detailed information on specific dosage regimens.

Rheumatoid Arthritis

For the management of rheumatoid arthritis, a single test dose of methotrexate may be given prior to initiation of therapy to detect possible sensitivity to adverse effects associated with the drug. Optimum dosage has not been fully established and dosage must be based on individual requirements and response. Patients receiving methotrexate therapy for rheumatoid arthritis must be constantly supervised by a physician who is experienced in the use of antineoplastic agents. The mnemonic dispensing packages (Rheumatrex Dose Pack) may be used for initial methotrexate therapy and are suitable for maintenance therapy in patients receiving weekly methotrexate doses of 5-20 mg; however, use of these dispensing packages is not recommended for titration to weekly doses higher than 20 mg. To avoid potentially lethal overdosage, patients should be instructed carefully about their dosage regimen, paying particular attention to the frequency of administration.

For the management of rheumatoid arthritis, methotrexate is administered in low-dose, intermittent (i.e., weekly rather than daily) regimens. The usual initial dosage in adults is 7.5 mg orally once weekly. This dosage may be administered either in a single-dosage schedule consisting of a single 7. 5-mg oral dose once weekly or in a divided-dosage schedule consisting of 2.5 mg of methotrexate administered orally at 12-hour intervals for 3 doses each week. Dosage in either the single- or divided-dosage schedule may be gradually increased until an optimum therapeutic response is achieved. However, dosage usually should not exceed 20 mg weekly, since higher dosages have been associated with a substantially increased incidence and severity of serious adverse reactions (e.g., bone marrow suppression). After an optimum response to the drug is achieved, the weekly dosage should be reduced to the lowest possible effective level. Therapeutic response in patients with rheumatoid arthritis usually is apparent within 3-6 weeks, but optimum response may not be achieved for another 3 or more months of therapy. The optimum duration of therapy is unknown; however, limited data from long-term clinical studies indicate that initial clinical improvement may be maintained for prolonged periods (e.g., 2 years or longer) with continued methotrexate therapy. Following discontinuance of the drug, rheumatoid arthritis usually worsens within 3-6 weeks.

Parenteral methotrexate regimens in the management of rheumatoid arthritis are variable, but have often consisted of 7.5-15 mg given IM once weekly in adults.

Crohn's Disease

For the management of Crohn's disease, methotrexate has been administered in low-dose, intermittent (i.e., weekly rather than daily) regimens. For the management of chronically active, refractory Crohn's disease, methotrexate has been administered once weekly either IM in a dosage of 25 mg for 16 weeks or orally in a dosage of 12.5-22.5 mg for up to 1 year. For maintenance therapy of Crohn's disease, an IM methotrexate dosage of 15 mg weekly has been used.

Cautions

The major toxic effects of methotrexate are on normal, rapidly proliferating tissues, particularly of the bone marrow and lining of the GI tract. These adverse effects generally are dose related and are reversible if detected early. Ulcerations of the oral mucosa are usually the earliest signs of toxicity, but in some patients bone marrow depression coincides with or precedes the appearance of mouth lesions.

Hematologic Effects

Leukopenia, thrombocytopenia, anemia, and hemorrhage from various sites may result from methotrexate therapy and may develop rapidly. In one study using single IV doses of methotrexate, the nadir of hemoglobin concentrations occurred in 6-13 days and was followed by recovery; reticulocytes reached their nadir in 2-7 days followed by recovery with rebound between 9 and 19 days. Leukocytes generally had two periods of depression; the first occurred in 4-7 days with recovery in 7-13 days and the second in 12-21 days with recovery in 15-29 days. Platelets reached their minimum in 5-12 days and recovered in number in 15-27 days.

Thrombocytopenia has been reported in approximately 5%, leukopenia and pancytopenia in approximately 1.5%, and decreased hematocrit and epistaxis in less than 1% of patients receiving 12-18 weeks of methotrexate for the management of rheumatoid arthritis.

GI Effects

Toxic effects of methotrexate on oral and GI mucosa are manifested by gingivitis, glossitis, pharyngitis, stomatitis, enteritis, ulcerations and bleeding of the mucous membranes of the mouth or other portions of the GI tract, abdominal distress, anorexia, nausea, vomiting, hematemesis, diarrhea, and melena. If ulcerative stomatitis or diarrhea occurs, methotrexate therapy must be interrupted in order to prevent hemorrhagic enteritis and death from intestinal perforation.

Pancreatitis also has been reported in patients receiving methotrexate.

Hepatic Effects

Methotrexate therapy has been associated with both acute and chronic hepatotoxicity. Acutely, elevations in serum aminotransferase (transaminase) concentrations frequently occur 1-3 days after a dose of the drug. Such elevations generally are transient, asymptomatic, and do not appear to be predictive of subsequent hepatic damage. Elevated liver function test results reportedly occurred in approximately 15% of patients receiving 12-18 weeks of methotrexate for the management of rheumatoid arthritis.

Hepatotoxicity manifested as hepatic fibrosis or cirrhosis or other histologic changes in the liver has occurred during long-term methotrexate therapy; such hepatotoxicity may require hepatic allotransplantation and can be fatal. In patients with psoriasis, when such changes occur, they often may not be preceded by symptoms of hepatotoxicity or abnormal liver function test results; in patients with rheumatoid arthritis, prolonged, substantial abnormalities in liver function test results may precede appearance of hepatic fibrosis or cirrhosis. Chronic hepatotoxicity generally has been associated with prolonged (2 years or longer) methotrexate therapy and cumulative doses of 1.5 g or more. Although accurate estimates of the incidence of chronic hepatotoxicity currently are not available, the incidence appears to be greater in patients receiving frequent (e.g., daily), small doses of the drug (such as the daily-dosage regimen used for psoriasis) than in those receiving intermittent regimens (such as those used for neoplastic disease and possibly rheumatoid arthritis). The risk of developing chronic hepatotoxicity in patients receiving methotrexate therapy for the management of psoriasis appears to be related to the cumulative dose of the drug, and presence of concurrent conditions such as alcoholism, obesity, or diabetes as well as advanced age appear to contribute to this risk. Although clinical experience is limited, these risk factors also may apply to patients receiving methotrexate therapy for the management of rheumatoid arthritis. In one retrospective analysis in a limited number of patients with rheumatoid arthritis who underwent periodic percutaneous liver biopsy as routine monitoring for potential hepatotoxicity while receiving intermittent methotrexate regimens for an average of 32 months, progressive hepatic changes, principally progression to mild to moderate fatty infiltration with portal inflammation, occurred in about 20% of these patients; alterations in liver function test results were not predictive of such changes. In this study, fibrosis that developed in patients with rheumatoid arthritis was considered mild and no patient with rheumatoid arthritis developed cirrhosis; however, the drug was discontinued in most patients when fibrosis was evident and additional study and experience are necessary to better elucidate the potential risk of hepatotoxicity associated with methotrexate therapy for arthritis.

Although various pathologic hepatic changes including atrophy, necrosis, fatty changes, fibrosis, and cirrhosis have been observed in patients with methotrexate-induced hepatotoxicity, no specific pathologic finding appears to be characteristic of methotrexate hepatotoxicity. The rate of progression of hepatic lesions with continued therapy and the potential reversibility of such lesions following discontinuance of the drug currently are not known.(See Cautions: Precautions and Contraindications.)

Respiratory Effects

Pulmonary toxicity, which can progress rapidly and is potentially fatal, has been associated with methotrexate therapy. Adverse pulmonary effects, including pulmonary fibrosis and acute or chronic interstitial pneumonitis, appear to occur at any time during therapy at any dosage of the drug, including low dosages. Although the clinical presentation of methotrexate-induced pulmonary toxicity is variable, manifestations commonly include fever, cough (especially one that is dry and nonproductive), dyspnea, chest pain, hypoxemia (which can be severe), and/or radiographic evidence of pulmonary infiltrates (usually diffuse and/or alveolar). Lung biopsies have revealed variable degrees of interstitial inflammation, granulomatous inflammation, and/or fibrosis. Because patients with rheumatoid arthritis may have underlying interstitial pulmonary changes associated with their disease, it may be difficult to differentiate such changes from potential methotrexate-induced changes; however, rheumatoid changes generally progress more slowly. In addition, a potential association between preexisting rheumatoid pulmonary changes and susceptibility to methotrexate-induced pulmonary toxicity has been suggested but requires further elucidation.

The possibility of methotrexate-induced pulmonary toxicity should be considered in any patient who develops pulmonary manifestations (e.g., dry, nonproductive cough; dyspnea) while receiving the drug. If such manifestations occur, methotrexate should be discontinued and careful clinical evaluation of the patient performed, including exclusion of possible infectious causes. Management of methotrexate-induced pulmonary toxicity mainly is supportive and may include mechanical ventilation; limited evidence suggests that administration of relatively high dosages of corticosteroids may provide some benefit, but additional experience is necessary. In addition, pulmonary toxicity induced by the drug may not be fully reversible and fatalities have been reported.

Dermatologic and Sensitivity Reactions

Severe, occasionally fatal cutaneous or sensitivity reactions (e.g., toxic epidermic necrolysis, Stevens-Johnson syndrome, exfoliative dermatitis, skin necrosis, erythema multiforme) have been reported in pediatric and adult patients within days of receiving single or multiple oral, IM, IV, or intrathecal doses of methotrexate. These reactions occurred following high-, intermediate-, or low-dose methotrexate therapy in patients with neoplastic or non-neoplastic diseases. Recovery has been reported after discontinuance of the drug. Other adverse dermatologic effects of methotrexate include erythematous rashes, pruritus, dermatitis, urticaria, folliculitis, photosensitivity, depigmentation, hyperpigmentation, petechiae, ecchymoses, telangiectasia, acne, and furunculosis. Alopecia occasionally occurs. Regrowth of hair usually occurs after methotrexate is discontinued but may require several months. Burning and erythema may occur in psoriatic areas for 1-2 days following each dose of the drug and psoriatic lesions may be aggravated by concomitant exposure to ultraviolet radiation. In addition, painful plaque erosions rarely have been reported in patients receiving methotrexate for the treatment of psoriasis.

Effects following Intrathecal Administration

Following intrathecal administration of methotrexate, acute chemical arachnoiditis manifested by headache, back pain, nuchal rigidity, and/or fever; subacute myelopathy manifested by paraparesis/paraplegia involving one or more spinal nerve roots; chronic leukoencephalopathy (which may be progressive and even fatal) manifested by confusion, irritability, somnolence, ataxia, dementia, and occasionally seizures and coma; and increased CSF pressure have occurred. Systemic toxicity also may occur following intrathecal and intra-arterial administration. Leukoencephalopathy, manifested by mental confusion, tremors, ataxia, irritability, somnolence, and seizures, and rarely progressing to coma and death, has been reported in patients receiving simultaneous oral and intrathecal methotrexate therapy. Leukoencephalopathy also has occurred following IV administration of methotrexate to patients who had received craniospinal irradiation. In addition, chronic leukoencephalopathy also has been reported in patients receiving repeated high doses of methotrexate with leucovorin rescue, but without cranial irradiation. Discontinuance of methotrexate may not be associated with complete recovery.

Inadvertent intrathecal overdosage of methotrexate has occurred rarely. In cases in which the inadvertent intrathecal dose was less than 100 mg and the error was usually rapidly recognized and appropriate therapy promptly instituted, the patients experienced no or only mild neurotoxicity. In cases in which the dose exceeded 100 mg, severe neurotoxicity occurred, manifested as prompt burning or numbness in the lower extremities, stupor, agitation, seizures, and/or respiratory insufficiency;in some cases, brain damage or fatal necrotizing leukoencephalopathy resulted despite prompt treatment, but complete recovery following prompt and aggressive therapy has been reported.

Inadvertent intrathecal overdosage of methotrexate constitutes a medical emergency, requiring prompt treatment and management. Although data are limited, management may be guided by the dose administered, time elapsed since administration, and anticipated severity of neurotoxicity. Regardless of the dose administered, as soon as the overdose is recognized, a repeat lumbar puncture should be performed immediately and CSF allowed to drain to gravity.

The efficacy of CSF drainage alone as a means for removing the drug is a function of the dose administered and time elapsed since administration, and decreases as these factors increase. If the dose exceeds 100 mg, prompt neurosurgical intervention with ventriculolumbar perfusion following immediate CSF drainage should be considered; continuous CSF drainage or multiple CSF exchanges may also be considered but are not likely to be as effective.

Other treatment measures may include high-dose parenteral leucovorin calcium therapy to minimize systemic toxicity, corticosteroids to minimize CNS inflammatory reactions, and other supportive therapy as necessary. Efficacy of carboxypeptidase G2 (glucarpidase) has not been established in the management of severe overdoses of intrathecal methotrexate; however, successful use of the drug in this setting has been reported. Successful treatment with intrathecal glucarpidase in a 6-year-old patient who received a 600-mg dose of methotrexate intrathecally has been reported; the patient also was treated with CSF drainage, ventriculolumbar perfusion, IV dexamethasone, IV leucovorin calcium, and hydration and alkalinization. While the addition of leucovorin to the ventriculolumbar perfusion fluid has been suggested and employed, its value is not known and the possibility that it may be epileptogenic via this route of administration should be considered. Intrathecal administration of leucovorin is contraindicated, and the drug has contributed to at least one death when administered by this route. The possible benefits of prophylactic anticonvulsant therapy are probably outweighed by the potential for obscuring acute neurologic symptoms and causing additional adverse effects.

Cardiovascular Effects

Pericarditis, pericardial effusion, hypotension, and thromboembolic complications (e.g., thrombophlebitis; pulmonary embolism; arterial, cerebral, deep vein, or retinal vein thrombosis) have been reported in patients receiving methotrexate therapy.

Other Adverse Effects

Headaches, drowsiness, blurred vision, eye discomfort, conjunctivitis, severe visual changes of unknown etiology, tinnitus, malaise, undue fatigue, and dizziness may occur in patients receiving methotrexate. A transient acute neurologic syndrome manifested by confusion, hemiparesis, seizures, and coma has been reported in patients receiving high-dose methotrexate therapy. The exact cause of this stroke-like encephalopathy is not known; however, it has been suggested that the syndrome may have been related to hemorrhage or complications from intra-arterial catheterization. Other reported complications from intra-arterial infusion techniques include arterial spasm, thrombosis, hemorrhage, infection at the catheter site, and thrombophlebitis. Transient subtle cognitive dysfunction, mood alteration, unusual cranial sensations, leukoencephalopathy, or encephalopathy have been reported in some patients receiving low-dose methotrexate therapy.

Other reported adverse effects of methotrexate include chills and fever, sweating, arthralgia, myalgia, decreased resistance to infection, septicemia, upper respiratory infection, osteoporosis including aseptic necrosis of the femoral head, hypogammaglobulinemia, cystitis, dysuria, vaginal discharge, gynecomastia, loss of libido, impotence, diabetes, abnormal tissue cell changes, and even sudden death.

Severe nephropathy manifested by azotemia, hematuria, and renal failure may occur in patients receiving methotrexate; fatalities have been reported. In one study, postmortem examination revealed extensive necrosis of the epithelium of the convoluted tubules. In patients with renal impairment, methotrexate accumulation and increased toxicity or additional renal damage may occur.

Soft tissue necrosis and osteonecrosis have been reported rarely in patients receiving methotrexate. The risk of soft tissue necrosis and osteonecrosis associated with methotrexate may be elevated in patients receiving concomitant radiotherapy.

Elevations in serum uric acid concentrations may occur in patients receiving methotrexate as a result of cell destruction and hepatic and renal damage. In some patients, uric acid nephropathy and acute renal failure may result. Tumor lysis syndrome associated with other cytotoxic drugs (e.g., fludarabine, cladribine), also has been reported in patients with rapidly growing tumors who were receiving methotrexate. Pharmacologic and appropriate supportive treatment may prevent or alleviate this complication. Methotrexate also was reported to precipitate acute gouty arthritis in two patients being treated for psoriasis. Administration of large volumes of fluids, alkalinization of the urine, and/or administration of allopurinol may be useful in preventing acute attacks of hyperuricemia and uric acid nephropathy.

Nodulosis, vasculitis, and reversible lymphomas (see Precautions and Contraindications) have been reported rarely in patients receiving methotrexate. Sometimes fatal opportunistic infections have been reported in patients receiving methotrexate for neoplastic or non-neoplastic diseases. The most frequent infection was Pneumocystis carinii pneumonia; however, other infections (e.g., nocardiosis, histoplasmosis, cryptococcosis, herpes zoster, herpes simplex hepatitis, disseminated herpes simplex) also were reported.

Precautions and Contraindications

Methotrexate is a highly toxic drug with a very low therapeutic index and a therapeutic response is not likely to occur without some evidence of toxicity. The drug can produce hepatotoxicity, severe hematologic toxicity, and GI hemorrhage; severe infection and even death may result. When methotrexate is used in combination with other antineoplastic agents and/or radiation therapy, toxic reactions may be more severe than would occur with methotrexate therapy alone. Concomitant use of methotrexate and radiation therapy may result in an increased risk of soft tissue necrosis and osteonecrosis (see Cautions: Other Adverse Effects). Although doses of methotrexate used in the management of psoriasis and rheumatoid arthritis are usually lower than those used in antineoplastic chemotherapy, severe toxicity may occur in any patient receiving the drug and deaths have been reported with the use of methotrexate in the management of malignancy, psoriasis, and rheumatoid arthritis.

Since methotrexate may produce severe toxicity, which may be fatal, the manufacturer states that the drug should only be used in patients with life-threatening neoplastic diseases or in those with severe, recalcitrant, disabling psoriasis or rheumatoid arthritis that is not adequately responsive to other forms of therapy.

The use of high-dose methotrexate regimens employed in the adjunctive treatment of osteosarcoma requires a meticulous understanding of the risks associated with such therapy and of leucovorin rescue. Particular attention to leukocyte counts, serum bilirubin and ALT (SGPT) concentrations, presence of mucositis or persistent pleural effusions, renal function, hydration, urinary alkalinization, fluid and electrolyte balance, and pharmacokinetic monitoring must be ensured when such regimens are used. The manufacturer's labeling and published protocols should be consulted for specific recommendations, including dosage guidelines based on these findings.

Methotrexate must be used only under constant supervision by a clinician who is experienced in the use of antimetabolites. Patients should be fully informed of the risks involved and should be instructed to report promptly any symptoms of toxicity. Because methotrexate is a highly toxic drug, the manufacturers recommend that patients be given no more than a 7-day supply of the drug at one time or, if an intermittent regimen is used (i.e., weekly rather than daily doses), no more than a 1-month supply (e.g., using a mnemonic dispensing package); refills should be only by direct order (i.e., written or oral) of the prescribing clinician. In addition, patients receiving intermittent regimens consisting of weekly rather than daily doses of the drug for the management of psoriasis or rheumatoid arthritis should be carefully instructed about their regimen and the frequency of methotrexate administration since mistaken daily use of the drug has resulted in fatalities; patients should be provided with and encouraged to read a copy of the patient instructions supplied by the manufacturer.

Patients receiving methotrexate should be closely monitored for hematologic, renal, hepatic, and pulmonary toxicities, with complete hematologic studies, urinalysis, renal function tests, liver function tests, and chest radiographs. Liver biopsy and bone marrow aspiration studies may be advisable, especially in patients receiving high-dose or prolonged methotrexate therapy. Particular attention to close monitoring is recommended for patients with renal impairment or with pleural effusions or other third-space compartments (e.g., ascites) since elimination of the drug may be impaired. In addition, consideration should be given to evacuating accumulated fluid if possible in patients with substantial compartmental third-spacing prior to methotrexate therapy; monitoring serum concentrations of the drug, reducing drug dosage, or, occasionally, discontinuance of methotrexate also is recommended. Dehydrated patients also are at risk of increased serum methotrexate concentrations. The patient's bleeding time, coagulation time, blood group, and blood type should be on record in case the need for transfusion or surgery arises. If toxic effects or adverse reactions occur, dosage should be reduced or the drug discontinued and appropriate corrective measures taken; however, it should be considered that serious toxic reactions may occur in the absence of abnormal laboratory test results. Severe, occasionally fatal cutaneous reactions have been reported in patients receiving single or multiple oral, IM, IV, or intrathecal doses of methotrexate. These reactions usually occur within days of administration of the drug and recovery has been reported after discontinuance of methotrexate.(See Cautions: Dermatologic and Sensitivity Reactions.)

Hematologic studies must be performed prior to and at frequent intervals during methotrexate therapy. Complete blood cell counts, including differential and platelet counts, generally should be determined at least once weekly in patients receiving the drug for the treatment of neoplastic disease, and at least once monthly in patients receiving the drug for psoriasis or rheumatoid arthritis. If a profound drop in blood cell count occurs, the drug must be immediately discontinued and appropriate alternative therapy instituted. If profound leukopenia and fever occur, the patient should be closely observed and antibiotic therapy should be initiated if there are signs of infection. Blood or platelet transfusions may be necessary in patients with severe bone marrow depression.

There is poor correlation between liver function test results and chronic hepatotoxicity in patients receiving methotrexate, and liver scans are of minimal value in detecting methotrexate hepatotoxicity; liver biopsy is currently the only reliable measure of hepatotoxicity. Nonetheless, hepatic function must be determined prior to initiation of methotrexate and liver function tests, including serum albumin concentrations, should be repeated periodically throughout therapy (at 1- to 2-month intervals in patients treated for psoriasis or rheumatoid arthritis). In patients being treated for psoriasis, liver biopsy should be performed before instituting methotrexate or shortly thereafter (i.e., 2-4 months after). Repeat liver biopsies are recommended after a total cumulative dose of 1.5 g and after additional cumulative doses of 1-1.5 g. In patients with psoriasis, a relationship between abnormal liver function test results and hepatic fibrosis or cirrhosis has not been established, and prolonged, substantial abnormalities in liver function test results may not precede appearance of hepatic fibrosis or cirrhosis in such patients. When a pre-methotrexate liver biopsy is not feasible, a liver scan might be useful to detect occult liver disease. Because some patients may discontinue methotrexate after 2-4 months of therapy (due to adverse effects or lack of efficacy), pre-methotrexate liver biopsy might be postponed in patients with psoriasis until this initial period is completed; if long-term methotrexate therapy is anticipated, liver biopsy should then be performed. Abnormal liver function test results frequently occur 1-2 days following a dose of methotrexate, and it is recommended that liver function tests be performed at least 1 week after the last dose of the drug. Because these tests generally return to normal within a few days, repeat tests should be done before performing a liver biopsy. If substantial abnormal liver function test results develop and persist, methotrexate therapy should be withheld for 1-2 weeks and liver function tests repeated. Liver function test results should generally return to normal within 1-2 weeks following discontinuance of the drug; however, if substantial abnormal liver function test results persist, a liver biopsy is recommended.

The decision to perform liver biopsies during methotrexate therapy for rheumatoid arthritis must be carefully individualized. Age at first use of methotrexate and duration of therapy reportedly are risk factors for methotrexate-induced hepatotoxicity. Although unconfirmed to date, it is not known if other risk factors similar to those observed in patients with psoriasis also are present in patients with rheumatoid arthritis. In patients with a history of excessive alcohol consumption, those with prolonged, substantial abnormal liver function test results, or those with chronic hepatitis B or C, liver biopsy should be performed before instituting methotrexate therapy. In patients with rheumatoid arthritis, prolonged, substantial abnormal liver function test results may precede appearance of fibrosis or cirrhosis. In patients with normal liver function, history and physical examination, and no other risk factors (obesity, diabetes mellitus, impaired renal function, history of liver disease, history of IV drug abuse, family history of inheritable liver disease, history of significant exposure to known hepatotoxic drugs), a liver biopsy is recommended after a cumulative methotrexate dosage of approximately 1.5 g. In addition, a liver biopsy should be performed during therapy in patients with prolonged, substantial abnormal liver function test results or with serum albumin concentration below normal values (but whose rheumatoid arthritis is under control). If pre-methotrexate and the first post-methotrexate therapy biopsies show no serious abnormalities and the patient has no risk factors, repeat liver biopsies are recommended every 2-3 years or after additional cumulative dosages of 1-1.5 g. Patients with grade I, II, or IIIA pathologic changes may continue to receive methotrexate therapy, but some clinicians state that those with grade IIIA changes should have a repeat liver biopsy after approximately 6 months of continuous methotrexate therapy. Patients with prolonged, substantial abnormal liver function test results who refuse liver biopsy or those with grade IIIB or IV pathologic changes should not receive further methotrexate therapy; however, occasional patients may require additional therapy with careful follow-up liver biopsies. Concomitant administration of methotrexate and other drugs with hepatotoxic potential including alcohol should be avoided.

Renal function tests should be performed prior to and periodically during methotrexate therapy (at 1- to 2-month intervals in patients with psoriasis or rheumatoid arthritis; more frequent monitoring usually is necessary in patients receiving methotrexate for the treatment of neoplastic disease). If renal impairment develops during methotrexate therapy, dosage should be reduced or the drug discontinued until renal function is improved or restored. In addition, tumor lysis syndrome associated with other cytotoxic drugs (e.g., fludarabine, cladribine) also has been reported in patients with rapidly growing tumors who were receiving methotrexate. Pharmacologic and appropriate supportive treatment may prevent or alleviate this complication.

Malignant lymphomas may occur in patients receiving low-dose methotrexate therapy; such lymphomas may regress following withdrawal of the drug and therefore may not require cytotoxic therapy. However, if lymphomas do not regress following discontinuance of methotrexate, appropriate therapy should be instituted. The manufacturers state that the potential benefits of methotrexate therapy (alone or in combination with other drugs) should be weighed against these potential risks, especially in children or young adults.

Since potentially fatal opportunistic infections (e.g., Pneumocystis carinii pneumonia) have been reported in patients receiving methotrexate therapy, the possibility of P. carinii pneumonia should be considered in patients who develop pulmonary symptoms. In addition, pulmonary function tests may be useful if methotrexate-induced pulmonary toxicity is suspected, particularly if baseline values are available. For other precautions associated with the potential toxic effects of the drug on the lungs, see Cautions: Pulmonary Effects.

The immunosuppressive action of methotrexate must be considered when evaluating use of the drug in patients in whom immune responses may be important or essential. In patients at high risk for acquired immunodeficiency syndrome (AIDS), an HIV antibody determination should be considered because of the potential for additive immunosuppression and increased risk of opportunistic infections. Two psoriatic patients developed tuberculosis while receiving methotrexate and it has been suggested that, in addition to a chest radiograph, a tuberculin skin test should be performed prior to initiation of methotrexate therapy. If the initial tuberculin test is positive, isoniazid preventive therapy should be initiated concomitantly with methotrexate therapy. Since an accurate evaluation of the tuberculin test is not possible in patients receiving methotrexate, chest radiographs should be repeated every 6 months during therapy in these patients.

Methotrexate should be used with extreme caution in patients with infection, peptic ulcer, ulcerative colitis, or debility, and in very young or geriatric patients. Methotrexate should be used with extreme caution, if at all, in patients with malignant disease who have preexisting liver damage or impaired hepatic function, preexisting bone marrow depression, aplasia, leukopenia, thrombocytopenia, or anemia; the drug is usually contraindicated in patients with impaired renal function. In the management of psoriasis or rheumatoid arthritis, methotrexate is contraindicated in patients with preexisting blood dyscrasias such as bone marrow hypoplasia, leukopenia, thrombocytopenia, or clinically important anemia; those with overt or laboratory evidence of immunodeficiency syndromes; and those with excessive alcohol consumption, alcoholic liver disease, or chronic liver disease.

Pediatric Precautions

The manufacturer states that safety and efficacy of methotrexate in pediatric patients for the management of any conditions other than cancer chemotherapy or polyarticular-course juvenile rheumatoid arthritis have not been established. Severe neurotoxic effects, manifested mainly by focal or generalized seizures, have been reported with increased frequency in pediatric patients with acute lymphoblastic leukemia who were receiving intermediate-dose IV methotrexate (1 g/m). Leukoencephalopathy and/or microangiopathic calcifications usually were observed in diagnostic imaging procedures of symptomatic patients.

Mutagenicity and Carcinogenicity

Methotrexate has been reported to cause chromosome damage. Although patients who had previously received methotrexate have conceived and borne normal children, both men and women should be advised to avoid conception during and immediately following methotrexate therapy so that normal production of germinal cells may be reestablished. (See Cautions: Pregnancy, Fertility, and Lactation.) It has been suggested that methotrexate may be carcinogenic; however, extensive epidemiologic studies are required before its carcinogenicity can be confirmed or refuted. Malignant lymphomas (e.g., non-Hodgkin's lymphoma) may occur in patients receiving low-dose oral methotrexate therapy; such lymphomas may regress following withdrawal of the drug and, therefore, may not require cytotoxic therapy. However, if lymphomas do not regress following discontinuance of methotrexate, appropriate therapy should be instituted. Therefore, the manufacturers state that the potential benefits of methotrexate therapy (alone or in combination with other drugs) should be weighed against these potential risks, especially in children or young adults.

Pregnancy, Fertility, and Lactation

Pregnancy

Abortion, fetal death, and/or congenital anomalies have occurred in pregnant women receiving methotrexate, especially during the first trimester of pregnancy. Methotrexate is contraindicated in the management of psoriasis or rheumatoid arthritis in pregnant women. Women of childbearing potential should not receive methotrexate until pregnancy is excluded. For the management of psoriasis or rheumatoid arthritis, methotrexate therapy in women should be started immediately following a menstrual period and appropriate measures should be taken in men or women to avoid conception during and for at least 12 weeks following methotrexate therapy. Both men and women receiving methotrexate should be informed of the potential risk of adverse effects on reproduction. Women of childbearing potential should be fully informed of the potential hazard to the fetus should they become pregnant during methotrexate therapy. In cancer chemotherapy, methotrexate should not be used in pregnant women or women of childbearing potential who might become pregnant unless the potential benefits to the mother outweigh the possible risks to the fetus.

Fertility

Defective oogenesis or spermatogenesis, transient oligospermia, menstrual dysfunction, and infertility have been reported in patients receiving methotrexate.

Lactation

Methotrexate is distributed into breast milk. Because of the potential for serious adverse reactions to methotrexate in nursing infants, the drug is contraindicated in nursing women.

Drug Interactions

Protein-bound Drugs and Weak Organic Acids

Because methotrexate is partly bound to serum proteins, its toxicity may be increased as a result of displacement by certain drugs such as salicylates, sulfonamides, sulfonylureas, phenytoin, phenylbutazone, tetracyclines, chloramphenicol, and aminobenzoic acid. Until the clinical importance of these findings is established, these drugs should be given cautiously in patients receiving methotrexate. In addition, the possibility that weak organic acids, including salicylates, may delay renal excretion of methotrexate and increase accumulation should be considered.

Nonsteroidal Anti-inflammatory Agents

Severe, sometimes fatal, toxicity (including hematologic and GI toxicity) has occurred following administration of a NSAIA (e.g., indomethacin, ketoprofen) concomitantly with methotrexate (particularly with high-dose therapy) in patients with various malignant neoplasms, psoriasis, or rheumatoid arthritis. The toxicity was associated with elevated and prolonged serum concentrations of methotrexate. The exact mechanism of the interaction remains to be established, but it has been suggested that NSAIAs may inhibit renal elimination of methotrexate, possibly by decreasing renal perfusion via inhibition of renal prostaglandin synthesis or by competing for renal elimination.

NSAIAs should be avoided in patients receiving relatively high dosages of methotrexate (e.g., those used in the treatment of neoplastic disease). The risk of concomitant low-dose, intermittent (e.g., 5-15 mg weekly) methotrexate therapy and NSAIAs has not been fully elucidated, but the drugs have been used concomitantly in many patients receiving methotrexate for the management of rheumatoid arthritis. However, in clinical studies in which the drugs were used concomitantly, the patients often were monitored closely and were receiving relatively stable dosages of NSAIAs; in addition, those with conditions that might predispose to methotrexate toxicity generally were excluded from the studies. NSAIAs should be used with caution in patients receiving low-dose methotrexate regimens such as those employed in the management of rheumatoid arthritis, and the possibility of increased and prolonged serum methotrexate concentrations and resultant toxicity should be considered. Although intermittent regimens also are used in the management of psoriasis, methotrexate dosages in such regimens usually are higher than those used in the management of rheumatoid arthritis and therefore are more likely to result in toxicity during concomitant NSAIA therapy; serious toxicity, including at least one death, has been reported in several patients with psoriasis receiving combined therapy with the drugs. Further study is needed to evaluate the interaction between NSAIAs and methotrexate.

Penicillins

Concomitant use of penicillins (e.g., amoxicillin, carbenicillin) may decrease renal clearance of methotrexate, presumably by inhibiting renal tubular secretion of the drug. Increased serum concentrations of methotrexate, resulting in GI or hematologic toxicity, have been reported in patients receiving low- or high-dose methotrexate therapy concomitantly with penicillins, and patients receiving the drugs concomitantly should be carefully monitored.

Proton-Pump Inhibitors

Although no formal drug interaction studies have been conducted with methotrexate and proton-pump inhibitors, data from case reports, population pharmacokinetic studies, and retrospective analyses suggest that concomitant use of methotrexate (particularly at high dosages) with proton-pump inhibitors (e.g., esomeprazole, omeprazole, pantoprazole) may decrease methotrexate clearance, resulting in elevated and prolonged serum concentrations of methotrexate and/or its metabolite hydroxymethotrexate and possibly leading to methotrexate toxicities. Increased concentrations of methotrexate and/or hydroxymethotrexate with or without associated adverse effects (e.g., renal toxicity, adverse hematologic effects, severe mucositis, myalgia) have been reported when methotrexate dosages ranging from 300 mg/m to 12 g/m were administered concomitantly with proton-pump inhibitors. Although the majority of reported cases occurred in patients receiving high dosages of methotrexate, methotrexate toxicity also has been reported following concomitant administration of low dosages of methotrexate (15 mg per week) with a proton-pump inhibitor. Therefore, the manufacturers of proton-pump inhibitors state that temporary discontinuance of proton-pump inhibitor therapy may be considered in some patients receiving high-dose methotrexate. Some clinicians specifically recommend withholding proton-pump inhibitor therapy for several days before, during, and for several days after methotrexate administration; in patients in whom acid suppression is clinically indicated during methotrexate therapy, substitution of a histamine H2-receptor antagonist (e.g., ranitidine) for the proton-pump inhibitor may be considered. Pending further evaluation, some clinicians state that these recommendations should extend to patients receiving low-dose methotrexate.

Other Drugs

Drugs with similar pharmacologic activity such as pyrimethamine should not be given to patients receiving methotrexate.

Concomitant use of other potentially hepatotoxic drugs (e.g., retinoids, azathioprine, sulfasalazine) and methotrexate may increase the risk of hepatotoxicity; patients receiving concomitant therapy with these drugs should be closely monitored.

Although concomitant use of methotrexate with cisplatin exhibits possible synergistic antineoplastic effects, cisplatin may alter renal elimination of methotrexate. Caution is advised if high-dose methotrexate is administered in conjunction with cisplatin for the treatment of osteosarcoma.

Co-trimoxazole should be used with caution in patients receiving methotrexate, since sulfonamides can displace methotrexate from plasma protein-binding sites resulting in increased free methotrexate concentrations.

It has been suggested that folic acid preparations including vitamin products may decrease the effectiveness of methotrexate therapy and should not be given to patients receiving methotrexate; however, there have been no clinical studies to support or refute this hypothesis.

Methotrexate increases plasma mercaptopurine concentrations; dosage adjustment may be necessary.

Probenecid diminishes renal tubular transport of methotrexate; patients should be carefully monitored during concomitant use of these agents.

Methotrexate may decrease clearance of theophylline; serum theophylline concentrations should be monitored in patients receiving theophylline concomitantly with methotrexate.

Vaccination with live virus vaccines generally should not be performed in patients receiving methotrexate. Disseminated vaccinia infection has been reported following smallpox vaccination in at least one patient receiving methotrexate. Although the antibody response to killed virus vaccines is not normal, partial or complete protection may still be attained and these vaccines may be used if necessary in patients receiving methotrexate.

Pharmacokinetics

Absorption

Oral absorption of methotrexate appears to be highly variable and dose dependent. While older studies demonstrated good absorption from the GI tract with relatively low oral doses of methotrexate, more recent studies indicate that the oral bioavailability of the drug may be below 50% even at relatively low doses (i.e., 15 mg/m or lower). The bioavailability of methotrexate decreases with increasing oral doses (suggesting the presence of a saturable absorption process) and absorption is substantially reduced at doses exceeding 80 mg/m. Studies investigating the use of divided doses of methotrexate in an attempt to improve the oral bioavailability of the drug have shown conflicting results. It has been suggested that poor bioavailability should be assumed with oral methotrexate doses of 100 mg/m or greater, regardless of the dosage schedule used. Food delays absorption and decreases peak serum concentrations of the drug. Peak serum concentrations of methotrexate generally are achieved in 1-2 hours following oral administration in adults.

Oral administration of methotrexate in pediatric patients with leukemia reportedly results in wide variability in the rate and extent of oral absorption. Oral bioavailability of 23-95%, with a 20-fold difference between the highest and lowest peak serum concentration measurements (range: 0.11-2.3 µM), has been reported in pediatric patients receiving oral methotrexate 20 mg/m for the treatment of leukemia. Substantial variability in the time to peak serum concentration also has been observed; in patients receiving methotrexate at an oral dose of 15 mg/m, the time to peak serum concentration ranged from 0.67-4 hours.

Methotrexate appears to be completely absorbed following IM administration at doses of up to at least 100 mg. Peak serum concentrations are achieved 30-60 minutes after IM administration of the drug. Serum concentrations following intra-arterial administration are similar to those achieved following IV administration.

Distribution

Methotrexate is actively transported across cell membranes. At serum methotrexate concentrations exceeding 0.1 mcmol/mL, passive diffusion becomes a major means of intracellular transport of the drug. The drug is widely distributed into body tissues with highest concentrations in the kidneys, gallbladder, spleen, liver, and skin. Following systemic administration of a single dose of methotrexate, the drug inhibits DNA synthesis in psoriatic epidermis for 12-16 hours. Following oral or IV administration of the drug to animals, synovial fluid methotrexate concentrations are higher in inflamed than in uninflamed joints; concurrent administration of salicylates did not affect distribution of methotrexate into joints, but pretreatment with prednisone reduced the amount of drug distributed into inflamed joints relative to that into normal joints. In patients receiving long-term, oral methotrexate therapy for rheumatoid arthritis, the ratio of synovial fluid to serum concentrations of methotrexate ranged from 0.9-1.2. Methotrexate distributes into third space fluids, and the presence of pleural effusions or ascites can substantially alter the disposition of the drug (see Pharmacokinetics: Elimination). Slow release of methotrexate from third space accumulations may prolong the terminal half-life and may increase the risk of drug toxicity with high doses (i.e., exceeding 250 mg/m).

Methotrexate is retained for several weeks in the kidneys and for months in the liver. Sustained serum concentrations and tissue accumulation of methotrexate may result from repeated daily doses. Following IV administration, an initial volume of distribution of approximately 0.18 L/kg and a steady-state volume of distribution of approximately 0.4-0.8 L/kg have been reported. According to the manufacturer, the drug does not reach therapeutic concentrations in the CSF when given orally or parenterally. However, high-dose systemic methotrexate therapy can result in peak CSF concentrations above the therapeutic threshold of 0.001 mcmol/mL and has been used to prevent meningeal leukemia and lymphoma. Following IV administration of methotrexate, CSF drug concentrations are dose related; a CSF concentration of 0.0001 mcmol/mL was reported after a dose of 500 mg/my 24-hour IV infusion, and CSF concentrations exceeding 0.01 mcmol/mL were observed following an IV bolus dose of 7500 mg/m. Intrathecal administration of methotrexate may result in potentially cytotoxic serum drug concentrations that can persist for 24-48 hours.

Methotrexate crosses the placental barrier. Methotrexate is distributed into breast milk; the highest reported breast milk plasma concentration ratio, which occurred 10 hours after administration of a 22.5-mg oral dose, was 0.08:1.(See Cautions: Pregnancy, Fertility, and Lactation.)

At serum concentrations of 0.001-0.1 mcmol/mL, about 50% of the drug is bound to plasma proteins (primarily albumin).

Elimination

In patients receiving methotrexate for the treatment of psoriasis or rheumatoid arthritis, or as low-dose antineoplastic therapy (i.e., less than 30 mg/m), a terminal half-life of about 3-10 hours has been reported. Higher doses of methotrexate have been associated with a longer elimination half-life of about 8-15 hours.

Plasma concentrations of methotrexate following high-dose IV infusion appear to decline in a biphasic manner. The half-life of the initial phase (t½α) averages 1.5-3.5 hours in patients with normal total body clearance and the half-life in the terminal phase (t½β) is about 8-15 hours.

After absorption, methotrexate undergoes hepatic and intracellular metabolism to form methotrexate polyglutamates, metabolites which by hydrolysis may be converted back to methotrexate. Methotrexate polyglutamates inhibit dihydrofolate reductase and thymidylate synthetase. Small amounts of these polyglutamate metabolites may remain in tissues for extended periods; the retention and prolonged action of these active metabolites vary among different cells, tissues, and tumors. In addition, small amounts of methotrexate polyglutamates may be converted to 7-hydroxymethotrexate; accumulation of this metabolite may become substantial following administration of high doses of methotrexate, since the aqueous solubility of 7-hydroxymethotrexate is threefold to fivefold lower than that of the parent compound. Following oral administration of methotrexate, the drug also is partially metabolized by the intestinal flora.

The drug is excreted primarily by the kidneys via glomerular filtration and active transport. Small amounts are excreted in the feces, probably via the bile. Methotrexate has a biphasic excretion pattern. Up to 92% of a single dose is excreted within 24 hours following IV administration followed by excretion of 1-2% of the retained dose daily. In one study, 58-92% of an IV methotrexate dose of 0.1-10 mg/kg was excreted in the urine within 24 hours. Only slightly less urinary excretion occurred following oral administration of 0.1 mg/kg. Following oral administration of 10 mg/kg, however, only 15% of the dose was excreted in the urine within 24 hours and 48% within 5 days. About 39% of the larger oral dose was recovered in the feces as compared to 7-9% following 0.1 mg/kg administered orally and 2-5% of 0.1-10 mg/kg administered IV. Enterohepatic recirculation of methotrexate may occur. Methotrexate excretion is impaired and accumulation occurs more rapidly in patients with impaired renal function, pleural effusions, or those with other third-space compartments (e.g., ascites). In addition, simultaneous administration of other weak organic acids such as salicylates may suppress methotrexate clearance.

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