terazosin 5 mg capsule

Uses

Hypertension

Terazosin hydrochloride is used alone or in combination with other classes of antihypertensive agents for the management of hypertension. Terazosin's efficacy in hypertensive patients appears to be similar to that of other α₁-adrenergic blocking agents, thiazide diuretics, β-adrenergic blocking agents, angiotensin-converting enzyme (ACE) inhibitors, and calcium-channel blocking agents. However, in one randomized, double-blind clinical study (the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial; [ALLHAT]), doxazosin, an α₁-blocker, was shown to be less effective in lowering mean systolic blood pressure (by about 2-3 mm Hg) than chlorthalidone, a thiazide-like diuretic. In order to achieve target blood pressure in hypertensive patients, use of doxazosin required additional hypotensive therapy more frequently than chlorthalidone. In addition, interim analysis (median follow-up: 3.3 years) of this study indicates that use of doxazosin in high-risk (at least 2 risk factors for coronary heart disease) hypertensive patients 55 years of age and older was associated with a higher risk of stroke and incidence of combined cardiovascular disease events (including twice the risk of congestive heart failure) than use of chlorthalidone. Study investigators concluded that such increased risk of congestive heart failure could not have been caused by the relatively small difference in the mean target systolic blood pressure observed in patients receiving doxazosin compared with those receiving chlorthalidone. Therefore, based on these findings, the trial's Data Safety and Monitoring Board recommended that the α-blocker treatment arm be terminated prematurely. The remaining antihypertensive arms (e.g., calcium-channel blockers, ACE inhibitors, diuretics) and lipid-lowering (pravastatin vs usual care) components of the study subsequently were completed and reported.

Because of established clinical benefits (e.g., reductions in overall mortality and in adverse cardiovascular, cerebrovascular, and renal outcomes), ACE inhibitors, angiotensin II receptor antagonists, calcium-channel blockers, and thiazide diuretics generally are considered the preferred drugs for the initial management of hypertension in adults. Although in the past α₁-blockers such as terazosin were recommended as one of several classes of first-line antihypertensive therapy or as initial therapy in selected hypertensive patients (e.g., those with symptomatic prostatic hyperplasia), current antihypertensive and urology guidelines no longer recommend α₁-blockers as preferred first-line therapy for any patients with hypertension, principally because of negative findings observed in ALLHAT. However, α₁-blockers are effective antihypertensive drugs and many experts still consider their use appropriate for the management of resistant hypertension as a component of combination therapy. Therapy with an α₁-blocker is most effective when used in combination with a diuretic. Although some experts state that an α₁-blocker may be a useful component of antihypertensive treatment regimens in older men with coexisting benign prostatic hyperplasia (BPH), the American Urology Association (AUA) states that monotherapy with these drugs is not optimal in hypertensive patients with lower urinary tract symptoms (LUTS) or BPH and that such conditions should be managed separately .

The beneficial effects of α₁-blockers on blood glucose and lipid concentrations may mitigate some of the adverse metabolic effects of diuretics, and α₁-blockers may offer some advantage in patients with underlying lipoprotein disorders (e.g., hypercholesterolemia) or in those with lipoprotein abnormalities induced by other antihypertensive agents (e.g., thiazide diuretics). The possibility that geriatric patients may be more susceptible than younger patients to the postural hypotensive effects of α₁-blockers should be considered in the selection of therapy. Blood pressure response to α₁-blockers appears to be comparable in white and black patients.

Benign Prostatic Hyperplasia

Terazosin hydrochloride is used to reduce urinary obstruction and relieve associated manifestations in patients with symptomatic benign prostatic hyperplasia (BPH, benign prostatic hypertrophy). For patients who can tolerate the potential cardiovascular and other effects of α₁-adrenergic blockade, the drug can effectively relieve mild to moderate obstructive manifestations (e.g., hesitancy, terminal dribbling of urine, interrupted stream, impaired size and force of stream, sensation of incomplete bladder emptying or straining) and urinary flow rates in a substantial proportion of patients and may be a useful alternative to surgery, particularly in those who are awaiting or are unwilling to undergo surgical correction of the hyperplasia (e.g., via transurethral resection of the prostate [TURP]) or who are not candidates for such surgery.

Therapy with α₁-blockers appears to be less effective in relieving irritative (e.g., nocturia, daytime frequency, urgency, dysuria) than obstructive symptomatology. In addition, therapy with the drugs generally can be expected to produce less subjective and objective improvement than prostatectomy, and periodic monitoring (e.g., performance of digital rectal examinations, serum creatinine determinations, serum prostate specific antigen [PSA] assays) is indicated in these patients to detect and manage other potential complications of or conditions associated with BPH (e.g., obstructive uropathy, prostatic carcinoma). While symptomatic improvement has been maintained for at least up to 2 years of terazosin therapy in some patients, the long-term effects of the drug on the need for surgery and on the frequency of developing BPH-associated complications such as acute urinary obstruction remain to be established.

Combination therapy with an α₁-blocker and 5α-reductase inhibitor (e.g., finasteride) has been more effective than therapy with either drug alone in preventing long-term BPH symptom progression; combined therapy also can reduce the risks of long-term acute urinary retention and the need for invasive therapy compared with α-blocker monotherapy.

Because many of the signs and symptoms of BPH can occur with carcinoma of the prostate and with certain genitourinary conditions, including prostatitis and neurologic disorders, the possibility of such conditions, particularly this carcinoma, should be ruled out in any patient for whom terazosin therapy for presumed hyperplasia is being considered.

Dosage and Administration

Administration

Terazosin hydrochloride is administered orally. Food has little, if any, effect on the extent of absorption of terazosin but may delay achievement of peak plasma concentrations by about 1 hour.

Dosage

Dosage of terazosin hydrochloride is expressed in terms of terazosin and must be individualized according to the patient's response and tolerance.

Hypertension

Usual Dosage

For the management of hypertension, terazosin dosage should be adjusted according to blood pressure response and tolerance. The usual initial adult dosage of the drug is 1 mg once daily at bedtime. Because of the risk of postural effects (see Cautions: Postural Effects), it is essential that therapy with the drug not be initiated with higher dosages.

If blood pressure is not adequately controlled at a terazosin dosage of 1 mg daily, the dosage may be increased gradually up to 5 mg once daily in adults, but each incremental increase should be delayed until blood pressure has stabilized at a given dosage; some patients may benefit from further titration up to 20 mg daily. Maintenance doses of the drug can be administered in the morning rather than at bedtime. Blood pressure should be monitored at the end of the dosing interval to ensure maintenance of control, and additional measurements 2-3 hours after dosing may be helpful in determining whether peak and trough responses are similar and in assessing potential manifestations (e.g., dizziness, palpitation) of an excessive response. If blood pressure response is diminished substantially 24 hours after a dose, an increased dose may provide adequate control. If necessary for optimal blood pressure control, the daily dose can be divided and administered every 12 hours.

The usual adult dosage of terazosin for the management of hypertension ranges from 1-20 mg daily administered as a single dose or in 2 divided doses daily. While higher dosages have been employed, those exceeding 20 mg daily do not appear to be associated with improved hypertensive control and those exceeding 40 mg daily have not been studied systematically. If terazosin is discontinued for several days or longer, therapy with drug should be reinstituted at 1 mg daily at bedtime and titrated as usual.

If terazosin is used for the management of hypertension in children, some experts recommend a usual initial dosage of 1 mg once daily. Dosage may be increased as necessary to a maximum dosage of 20 mg once daily.

Blood Pressure Monitoring and Treatment Goals

Careful monitoring of blood pressure during initial titration or subsequent upward adjustment in dosage of terazosin is recommended.

The goal of hypertension management and prevention is to achieve and maintain optimal control of blood pressure; specific target levels of blood pressure should be individualized based on consideration of multiple factors, including patient age and comorbidities, and the currently available evidence from clinical studies.

Benign Prostatic Hyperplasia

For the management of benign prostatic hyperplasia (BPH), the usual initial adult dosage of terazosin is 1 mg once daily at bedtime. Because of the risk of postural effects (see Cautions: Postural Effects), it is essential that therapy with the drug not be initiated with higher dosages. To achieve the desired improvement in symptoms and/or urinary flow rates, subsequent dosage may be increased in a stepwise manner to 2, 5, and 10 mg daily as necessary. Titration to a dosage of 10 mg once daily generally is required for adequate clinical response. A minimum of 4-6 weeks may be needed to adequately assess the response at this dosage, but some patients may not respond despite appropriate titration. While additional benefit occasionally may be observed by increasing the dosage to 20 mg daily, maximally tolerable and effective dosages have not been established and there currently is insufficient experience with this dosage in the management of BPH to draw definitive conclusions. In addition, there currently are insufficient data to support the use of dosages exceeding 20 mg daily in patients with an inadequate or no response at lower dosages. If terazosin therapy is discontinued for several days or longer, therapy should be restarted using the recommended initial dosage.

Dosage in Renal and Hepatic Impairment

Clinically important alterations in the pharmacokinetics of terazosin in patients with impaired renal function have not been observed to date, and modification of dosage in such patients generally does not appear to be necessary. In addition, administration of supplemental doses of the drug following hemodialysis does not appear to be necessary.

The effects, if any, of hepatic impairment on the pharmacokinetics of terazosin have not been elucidated, and the manufacturer makes no specific recommendations for modification of terazosin dosage in patients with hepatic impairment.

Dosage in Geriatric Patients

While the manufacturer makes no specific recommendations for titration of terazosin dosage in geriatric patients, patients in this age group generally are less tolerant of the postural hypotensive effects of α₁-adrenergic blocking agents because of impaired cardiovascular reflexes, and caution should be exercised. Therefore, dosage escalation in elderly patients generally should be slower than in younger adults. In addition, the elimination half-life may be prolonged and plasma clearance of the drug decreased in patients 70 years of age and older.

Cautions

Adverse effects occurring most frequently during terazosin hydrochloride therapy for hypertension include dizziness, headache, asthenia (weakness, tiredness, lassitude, fatigue), nasal congestion, peripheral edema, somnolence, nausea, and palpitation. In patients receiving the drug for benign prostatic hyperplasia (BPH), the most frequent adverse effects are dizziness, asthenia, headache, postural hypotension, and somnolence. The frequency of adverse effects in controlled clinical trials generally has been lower in patients receiving terazosin for BPH than in those receiving the drug for hypertension; however, dosages employed for this condition also generally have been lower than those for hypertension.

While adverse effects occur frequently in patients receiving terazosin, most are mild to moderate in severity, and discontinuance of the drug secondary to adverse effects was required in only 9% of patients with BPH and in only 13-21% of patients with hypertension during clinical trials. The principal reasons for discontinuance in patients with hypertension were postural effects (e.g., dizziness in about 3% of patients) and asthenia, palpitation, headache, and dyspnea each in about 1-2% of patients. In patients with BPH, the principal reasons for discontinuance were dizziness, headache, and blurred vision/amblyopia in 2, 1.1, and 0.6%, respectively, of patients and postural hypotension, syncope, vertigo, dyspnea, fever, nausea, and urinary tract infection each in 0.5% of patients. In controlled clinical trials in patients with hypertension, only dizziness (including postural effects), asthenia, blurred vision, nasal congestion, nausea, peripheral edema, palpitation, and somnolence occurred at rates significantly greater than those for placebo. Only asthenia, postural hypotension, dizziness, somnolence, nasal congestion/rhinitis, and impotence occurred significantly more frequently with the drug than with placebo in controlled clinical trials for BPH. The risk of postural hypotension and syncope appears to be higher in geriatric patients (i.e., those 65 years of age and older) than in younger patients. Asthenia and postural effects, including dizziness, appear to be dose related.

Postural Effects

Terazosin, like other α₁-adrenergic blocking agents, can cause marked hypotension, which may be accompanied by syncope and other postural effects. While syncope is the most severe orthostatic effect of the drug, other less severe symptoms, such as dizziness, lightheadedness, tachycardia, palpitation, and vertigo, also can be associated with terazosin-induced reductions in blood pressure. Syncope is uncommon when terazosin dosage is initiated at low levels and titrated slowly, but dizziness is frequent, occurring in about 20 or 10% of patients receiving the drug for hypertension or BPH, respectively, in controlled trials. Palpitation has been reported in 4.3% of hypertensive patients receiving terazosin, and tachycardia (especially in the standing position) and postural hypotension have been reported in 1-2% of such patients. Postural hypotension, vertigo, and syncope have been reported in about 4, 1.4, and 0.6% of patients, respectively, receiving the drug for BPH; however, in several clinical trials in such patients, the frequency of postural hypotension ranged from 3.7-5.2%.

Terazosin-induced postural hypotension is dose related, particularly likely in the upright position following an initial dose, and most likely to develop shortly after dosing (e.g., within 90 minutes), particularly during the initial week of therapy. With continued therapy after careful dosage titration, adaptation of reflex mechanisms to α₁-blockade develops and the risk of postural effects generally subsides. However, marked hypotension also can occur with subsequent dosage increases or after therapy is interrupted for more than a few days. Occasionally, syncopal episodes have been preceded by episodes of severe supraventricular tachycardia with heart rates of 120-160 bpm. In addition, the possibility exists that hemodilution induced by the drug may contribute to postural hypotension. While the adverse effect profiles of terazosin and prazosin generally appear to be similar, it has been suggested that postural effects may be less likely with terazosin in part because of the drug's slower onset of action and reduced affinity for α₁-receptors; however, additional study and experience are needed to elucidate the relative risks of postural effects.

The risk of first-dose syncope with α₁-adrenergic blocking agents generally can be minimized by initiating therapy at low doses (i.e., 1 mg of terazosin daily), lessening the level of salt restriction and avoiding diuretics just prior to initiation of α₁-blocker therapy, and administering initial doses at bedtime. It is essential that terazosin therapy not be initiated at dosages exceeding 1 mg daily and that dosage escalation be slow. If syncope develops, the patient should be placed in the recumbent position and treated supportively as necessary. Patients should be advised to lie or sit down if they develop any postural symptom (e.g., dizziness, vertigo) and to exercise caution upon standing from a sitting or supine position. Patients also should be advised to contact their physician if dizziness, lightheadedness, or palpitations become bothersome since dosage adjustment may be necessary. Other antihypertensive therapy, especially verapamil (see Precautions and Contraindications), should be added cautiously in patients receiving terazosin.

In early trials in which increasing single terazosin doses up to 7.5 mg were administered at 3-day intervals, tolerance to the first-dose phenomenon did not necessarily develop, and first-dose postural effects were observed at all doses. In addition, syncope occurred in about 20% of patients at single-dose levels of 2.5, 5, or 7.5 mg, and a few patients developed severe orthostatic hypotension (blood pressure declining to 50/0 mm Hg) at these dosing levels. These effects occurred within 90 minutes of dosing in all cases.

Nervous System Effects

Besides dizziness (see Cautions: Postural Effects), headache is the most common adverse nervous system effect associated with terazosin therapy, occurring in about 16 or 5% of patients receiving the drug for hypertension or BPH, respectively. Asthenia (weakness, tiredness, lassitude, fatigue) occurs in 11.3 or 7.4% of such patients, respectively, and somnolenceoccurs in 5.4 or 3.6%, respectively. Paresthesia and nervousness occur in 2-3% of patients receiving the drug for hypertension, and depression occurs in 0.3%. Anxiety and insomnia have been reported occasionally, but a causal relationship to the drug has not been established.

GI Effects

Nausea is the most common adverse GI effect of terazosin, occurring in 4.4 or 1.7% of patients receiving the drug for hypertension or BPH, respectively. Constipation, diarrhea, dry mouth, dyspepsia, flatulence, abdominal pain, and vomiting have been reported occasionally, but these effects have not been directly attributed to the drug.

Cardiovascular Effects

Besides postural effects of the drug (see Cautions: Postural Effects), other cardiovascular effects reported with terazosin include peripheral edema in about 6 or 1% of patients receiving the drug for hypertension or BPH, respectively, and tachycardia and nonperipheral edema in about 1-2% of those receiving the drug for hypertension. Arrhythmia, chest pain, and vasodilation have been reported occasionally, but a causal relationship has not been established. While clinically important nonpostural decreases in blood pressure generally are not observed in normotensive patients receiving the drug for BPH, some reduction may occur, and hypotension develops in less than 1% of patients. Atrial fibrillation has been reported during postmarketing surveillance in patients receiving terazosin.

Dermatologic and Sensitivity Reactions

Adverse dermatologic effects have been reported occasionally in patients receiving terazosin, but a causal relationship to the drug has not been established. Such effects include facial edema, pruritus, and rash.

Allergic reactions, including anaphylaxis, have been reported rarely in patients receiving terazosin.

Musculoskeletal Effects

Back pain or flu-like syndrome occurs in 2.4% of patients receiving terazosin for hypertension or BPH, respectively. These effects also have been reported in hypertensive patients, but a causal relationship to the drug could not be established. Other musculoskeletal effects for which a causal relationship has not been established include neck or shoulder pain, arthralgia, arthritis, joint disorder, and myalgia. Pain in the extremities also has been reported.

Respiratory Effects

Nasal congestion/rhinitis occurs in about 6 or 2% of patients receiving terazosin for hypertension or BPH, respectively, and dyspnea occurs in about 3.1 and 1.7%, respectively. Sinusitis occurs in 2.6% of hypertensive patients receiving the drug. Occasionally, cold symptoms, bronchitis, epistaxis,cough, and pharyngitis have been reported, but these effects have not been directly attributed to the drug.

Genitourinary Effects

Impotence is the most common adverse genitourinary effect of terazosin, occurring in 1.2 or 1.6% of patients receiving the drug for hypertension or BPH, respectively. Priapism (painful penile erection sustained for hours and unrelieved by sexual intercourse or masturbation) has been reported rarely (probably less frequently than 1 per several thousand patients) in patients receiving an α₁-adrenergic antagonist (e.g., terazosin). Urinary tract infection was reported in 1.3% of patients with BPH receiving the drug, but this frequency was less than that reported with placebo. Urinary tract infection also has been reported in hypertensive patients receiving terazosin but could not be directly attributed to the drug. Other adverse genitourinary effects for which a causal relationship has not been established include urinary frequency and urinary incontinence (principally in postmenopausal women).

Ocular and Otic Effects

Blurred vision/amblyopia occurs in 1.6 or 1.3% of patients receiving terazosin for hypertension or BPH, respectively. Visual abnormalities, conjunctivitis, and tinnitus have been reported occasionally but have not been directly attributed to the drug.

Hematologic Effects

Small decreases in hemoglobin concentration, hematocrit, leukocyte count, and total protein and albumin concentrations have been observed following administration of terazosin and were suggestive of hemodilution. Similar changes have been observed with other α₁-adrenergic blocking agents and attributed to hemodilution. Thrombocytopenia has been reported during postmarketing surveillance in patients receiving terazosin.

Other Adverse Effects

Weight gain (in both males and females) occurs in 0.5% of patients receiving terazosin for hypertension or BPH, and decreased libido occurs in 0.6% of those receiving the drug for hypertension. Some evidence suggests that the likelihood of weight gain may increase with increasing dosage and/or duration of therapy in some patients. Other adverse effects have been reported occasionally with terazosin but have not been directly attributed to the drug. Such effects include fever, gout, and sweating.

Precautions and Contraindications

Patients should be warned of the possibility of terazosin-induced postural dizziness and measures to take if it develops (e.g., sitting, lying down).(See Cautions: Postural Effects.) During initiation of terazosin therapy, the patient should be cautioned to avoid, for 12 hours after the first dose, subsequent dosage increases, and resumption of therapy, situations where injury could result (e.g., driving, hazardous tasks) if syncope were to occur. If syncope occurs, the patient should be placed in the recumbent position and treated supportively as necessary. Patients who engage in potentially hazardous activities such as operating machinery or driving motor vehicles should be warned about possible somnolence, drowsiness, or dizziness.

While the manufacturer questions the need for caution, some clinicians state that α₁-adrenergic blocking agents should be avoided in patients with micturition-associated syncope because of the risk of exaggerated postural effects.

Patients also should be advised that priapism has been reported rarely in patients receiving an α₁-adrenergic antagonist (e.g., terazosin). Priapism is a medical emergency that could result in penile tissue damage and permanent loss of potency if not treated immediately; therefore, patients should be advised to report promptly to their clinician or, if their clinician is unavailable, to seek alternative immediate medical attention if an erection occurs that persists longer than several (e.g., 4-6) hours or is painful.

The possibility of carcinoma of the prostate and other conditions associated with manifestations that mimic those of BPH should be excluded in any patient for whom terazosin therapy for presumed BPH is being considered.

Caution should be exercised when adding terazosin to a preexisting antihypertensive regimen or when adding other hypotensive agents to a terazosin regimen in order to avoid a possible rapid fall in blood pressure and exacerbation of postural effects. Dosage reduction and/or retitration of therapy may be necessary. Particular caution may be necessary when terazosin and verapamil are used concomitantly because of an added potential pharmacokinetic interaction (i.e., verapamil-induced increases in plasma terazosin concentrations).

Terazosin is contraindicated in patients with known sensitivity to the drug or any other quinazoline derivative (e.g., doxazosin, prazosin).

Pediatric Precautions

The manufacturer states that safety and efficacy of terazosin in patients younger than 21 years of age have not been established.

Geriatric Precautions

Geriatric patients (e.g., those 65 years of age and older) may be particularly susceptible to postural as well as certain other adverse effects of terazosin.(See Dosage and Administration: Dosage.)

Mutagenicity and Carcinogenicity

There was no evidence of terazosin-induced mutagenicity in in vitro and in vivo test systems (Ames test, in vivo cytogenetics, dominant lethal test in mice, in vivo Chinese hamster chromosome aberration test, V79 forward mutation assay).

Oral terazosin dosages of 250 mg/kg daily (695 times the maximum recommended human dosage of 20 mg daily adjusted for a 55-kg man) for 2 years were associated with an increase in benign adrenal medullary tumors in male rats; females were unaffected. The drug was not oncogenic in mice receiving oral dosages of 32 mg/kg daily for 2 years. The absence of mutagenicity in a battery of in vivo and in vitro tests, of tumorigenicity of any cell type in the mouse carcinogenicity assay, of increased total tumor incidence in rats or mice, and of proliferative adrenal lesions in female rats suggests that the observed increase in benign medullary tumors is a male-rat species-specific effect. In addition, numerous other drugs and chemicals have been associated with increased benign adrenal medullary tumors in male rats without evidence of carcinogenic effects in humans.

Pregnancy, Fertility, and Lactation

Pregnancy

Terazosin was not teratogenic in rats or rabbits at oral dosages up to 1330 or 165 times the maximum recommended human dosage, respectively. Fetal resorptions occurred in rats at an oral dosage of 480 mg/kg daily, which is approximately 1330 times the maximum recommended human dosage. Increased fetal resorptions, decreased fetal weight, and increased supernumerary ribs were observed in offspring of rabbits that received 165 times the maximum recommended human dosage. These fetal findings were most likely secondary to maternal toxicity. There are no adequate and controlled studies in pregnant women, and safety of terazosin during pregnancy has not been established. The drug should be used during pregnancy only when potential benefits justify the possible risks to the mother and fetus.

In a perinatal and postnatal development study in rats, there was an increased frequency of deaths in the offspring during the first 3 weeks postpartum at a maternal oral terazosin dosage of 120 mg/kg daily (more than 300 times the maximum recommended human dosage).

Fertility

In reproduction studies in rats receiving oral terazosin dosages of 8, 30, or 120 mg/kg daily, failure to sire litters was observed in males receiving the latter 2 dosages, but testicular weight and morphology were unaffected. However, vaginal smears at these latter dosages appeared to contain less sperm than smears from control matings, and a positive correlation between sperm count and subsequent pregnancy was observed. An increase in testicular atrophy has been observed in rats receiving terazosin dosages of 40 or 250 mg/kg daily but not in those receiving 8 mg/kg daily (more than 20 times the maximum recommended human dosage). Testicular atrophy also was observed in dogs receiving 300 mg/kg daily (more than 800 times the maximum recommended human dosage) for 3 months but not with 1 year of administration at 20 mg/kg daily. Such atrophy also has been observed with prazosin.

Lactation

Since it is not known whether terazosin is distributed into milk, the drug should be used with caution in nursing women.