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Uses

Major Depressive Disorder

Venlafaxine hydrochloride is used in the treatment of major depressive disorder. Efficacy of venlafaxine conventional tablets for the management of major depression has been established in several placebo-controlled studies in outpatient settings in patients who had major depression and in 1 placebo-controlled study in a hospital setting in patients who had major depression with melancholia. Efficacy of venlafaxine extended-release capsules for the treatment of major depression also has been established by controlled studies of 8-12 weeks' duration in outpatient settings; however, the safety and efficacy of venlafaxine extended-release capsules in hospitalized patients with major depression have not been adequately evaluated.

In 4 studies of 6 weeks' duration in adult outpatients with major depression, venlafaxine in dosages of 75-225 mg daily administered in 2 or 3 divided doses as conventional tablets was found to be superior to placebo on at least 2 of the following 3 clinical measures of depression: Hamilton Depression Rating Scale (HAM-D) total score, HAM-D depressed mood item, and the Clinical Global Impression (CGI) Severity of Illness Scale. In these studies, higher dosages (i.e., dosages exceeding 225 mg daily) were not associated with greater response. In 2 short-term (8 or 12 weeks), placebo-controlled, flexible-dose (75-225 mg daily) studies with venlafaxine extended-release capsules in adult outpatients, venlafaxine was found to be superior to placebo on the same clinical measures of depression that were used in the studies of venlafaxine conventional tablets, as well as on the Montgomery-Asberg Depression Rating Scale (MADRS) total score and certain factors of the HAM-D, including the anxiety/somatization factor, the cognitive disturbance factor, the retardation factor, and the psychic anxiety score.

Venlafaxine also has been shown to be superior to placebo in the management of major depression with melancholia in a hospital setting. In a study of 4 weeks' duration, 65% of hospitalized patients with major depressive disorder and melancholia who received venlafaxine 150-375 mg daily (mean dosage of 350 mg daily) administered in 3 divided doses as conventional tablets had at least a 50% reduction in MADRS total score compared with 28% of those who received placebo. Patients who participated in this study had a mean baseline MADRS total score of 35 (range: 26-48); those with a baseline score of 4 or greater on the suicidal thought item of the MADRS were excluded from the study.

Results of long-term, relapse prevention studies in outpatients with major depression indicate that venlafaxine's antidepressant effects are maintained for up to 1 year. In these studies, patients who responded to an initial 8-week course of venlafaxine 75-225 mg once daily (as extended-release capsules) or an initial 26-week course of venlafaxine 100-200 mg daily in 2 divided doses (as conventional tablets) were randomized to receive either venlafaxine (same dosage range) or placebo. Patients receiving venlafaxine experienced substantially lower relapse rates than those receiving placebo. Relapse was defined in clinical studies with venlafaxine conventional tablets as a score of 4 or greater on the CGI Severity of Illness Scale and in clinical studies with venlafaxine extended-release capsules as a reappearance of major depressive disorder as defined by DSM-IV criteria and a CGI Severity of Illness score of 4 or greater (i.e., moderately severe depression), 2 consecutive scores of 4 or greater on the CGI Severity of Illness Scale, or a final CGI Severity of Illness score of 4 or greater for any patient who withdrew from the study for any reason.

For further information on treatment of major depressive disorder and considerations in choosing the most appropriate antidepressant for a particular patient, including considerations related to patient tolerance, patient age, and cardiovascular, sedative, and suicidal risk, .

Generalized Anxiety Disorder

Venlafaxine hydrochloride is used in the treatment of generalized anxiety disorder. Efficacy of venlafaxine extended-release capsules for the management of generalized anxiety disorder has been established in 4 randomized, multicenter, placebo-controlled studies of 2 or 6 months' duration in adult outpatients who met DSM-IV criteria for generalized anxiety disorder. Three studies employed fixed venlafaxine dosages, and the other employed a flexible dosing schedule. In the flexible-dose study, approximately 69% of patients receiving venlafaxine (75-225 mg daily as extended-release capsules) were categorized as responders (defined as a 40% or greater reduction from baseline in the Hamilton Rating Scale for Anxiety [HAM-A] total score or a score of 1 [''very much improved''] or 2 [''much improved''] on the Clinical Global Impressions [CGI] Global Improvement Scale) during weeks 6-28 of therapy compared with 42-46% of those receiving placebo. In separate clinical studies of 2 or 6 months' duration employing fixed dosages of venlafaxine (37.5, 75, 150, or 225 mg daily as extended-release capsules), venlafaxine was shown to be substantially more effective than placebo on HAM-A total score, both the HAM-A anxiety and tension items, and the CGI Scale. While a relationship between dosage (over the dosage range of 75-225 mg daily) and efficacy in generalized anxiety disorder has not been definitively established, dosages of 37.5 mg daily were not as consistently effective in one study as dosages of 75 or 150 mg daily.

Social Phobia

Venlafaxine hydrochloride is used in the treatment of social phobia (social anxiety disorder). Efficacy of venlafaxine extended-release capsules in the treatment of social phobia has been established in 2 multicenter, placebo-controlled studies of 12 weeks' duration in adult outpatients who met DSM-IV criteria for social phobia. In these studies, venlafaxine (75-225 mg daily administered as extended-release capsules) was substantially more effective than placebo, as determined by change from baseline in the Liebowitz Social Anxiety Scale (LSAS) total score.

Subgroup analysis of these controlled studies in adult outpatients with social anxiety disorder did not reveal any evidence of gender-related differences in treatment outcome; there was insufficient information to determine the effect of age or race on outcome in these studies.

Panic Disorder

Venlafaxine hydrochloride is used in the treatment of panic disorder with or without agoraphobia. Efficacy of venlafaxine extended-release capsules in the treatment of panic disorder has mainly been established in 2 multicenter, double-blind, placebo-controlled studies of 12 weeks' duration in adult outpatients who met DSM-IV criteria for panic disorder with or without agoraphobia. Venlafaxine was given in a fixed dosage of 75 or 150 mg once daily as extended-release capsules in one study and in a fixed dosage of 75 or 225 mg once daily as extended-release capsules in the other study. Venlafaxine was found to be substantially more effective than placebo, as determined by percentage of patients free of full-symptom attacks on the Panic and Anticipatory Anxiety Scale (PAAS), mean change from baseline on the Panic Disorder Severity Scale (PDSS) total score, and the percentage of patients rated as responders on the Clinical Global Impressions (CGI) Improvement Scale. While a relationship between dosage (over the dosage range of 75-225 mg daily) and efficacy in panic disorder has not been definitively established, efficacy was established for each dosage studied in these 2 trials.

Subgroup analysis of these controlled studies in adult outpatients with panic disorder did not reveal any evidence of gender-related differences in treatment outcome; there was insufficient information to determine the effect of age or race on outcome in these studies.

In a longer-term study, patients meeting DSM-IV criteria for panic disorder who had responded during the 12-week open phase of a clinical trial with venlafaxine (75, 150, or 225 mg once daily as extended-release capsules) were randomly assigned to either continue receiving venlafaxine in the same dosage range or be switched to placebo and observed for relapse. Relapse was defined as having 2 or more full-symptom panic attacks per week for 2 consecutive weeks or having discontinued therapy due to loss of effectiveness as determined by the study investigators. Patients who continued receiving venlafaxine therapy experienced a significantly longer time to relapse than those receiving placebo in this study.

Vasomotor Symptoms

Venlafaxine has been used for the management of vasomotor symptoms in women with breast cancer and in postmenopausal women. Therapy with the drug has improved both the frequency and severity of vasomotor symptoms (hot flushes [ flashes]) in these women.

Most women receiving systemic antineoplastic therapy for breast cancer experience vasomotor symptoms, particularly those receiving tamoxifen therapy. In a randomized, double-blind, placebo-controlled study in 191 women with breast cancer (69% were receiving tamoxifen) who were experiencing 2 or more episodes of hot flushes daily, the percentage reductions in hot flush severity score at 4 weeks of treatment were 27% for placebo, 37% for venlafaxine 37.5 mg daily, 61% for venlafaxine 75 mg daily, and 61% for venlafaxine 150 mg daily. Comparisons among treatment groups showed that all 3 venlafaxine dosages were associated with a statistically significant reduction in hot flush frequency and severity; in addition, the 75-mg dosage was more effective than the 37. 5-mg dosage, but the 150-mg dosage provided no additional benefit. The role of venlafaxine in managing vasomotor symptoms in women with breast cancer relative to other nonhormonal therapies (e.g., selective serotonin-reuptake inhibitors [SSRIs], gabapentin) remains to be determined. Well-designed, comparative studies are needed to establish optimum nonhormonal therapy, both in terms of efficacy and patient tolerance of adverse effects in these women.

Because of the risks associated with hormone replacement therapy (HRT) for vasomotor symptoms in perimenopausal and postmenopausal women, alternative nonhormonal therapies are being investigated. In a randomized, double-blind, placebo-controlled study in 80 postmenopausal women who were experiencing more than 14 hot flushes weekly, 12 weeks of venlafaxine 75 mg daily was associated with a 51% reduction in hot flush score (patient's perception of hot flush interference with daily living). Although there also was a reduction in hot flush severity, the difference did not reach statistical significance. The role of venlafaxine therapy relative to other nonhormonal therapies (e.g., SSRIs, gabapentin) for postmenopausal vasomotor symptoms, both in terms of efficacy and safety, remains to be established.

Current evidence indicates that venlafaxine is well tolerated in the short-term treatment of vasomotor symptoms associated with breast cancer treatment and with menopause. The principal adverse effects associated with venlafaxine therapy in women with vasomotor symptoms have been dry mouth, decreased appetite, nausea, constipation, and difficulty sleeping. Additional study and experience are needed to further elucidate the role of venlafaxine relative to other nonhormonal therapies and to establish longer-term (i.e., beyond 4-12 weeks) efficacy and safety.

The possible role of venlafaxine in the management of vasomotor symptoms associated with antiandrogenic therapy in men with prostate cancer remains to be determined.

Obesity

Although substantial changes in appetite and weight have been reported in clinical studies of venlafaxine for the management of major depression, generalized anxiety disorder, social phobia, and panic disorder, the manufacturer states that the drug, alone or in combination with weight loss agents such as phentermine, is not indicated for the management of exogenous obesity. Concomitant use of venlafaxine and weight loss agents also is not recommended by the manufacturer because the safety and efficacy of these agents when used concomitantly have not been established.

Dosage and Administration

Administration

Venlafaxine hydrochloride is administered orally. To minimize GI intolerance (e.g., nausea), the manufacturer recommends that conventional venlafaxine tablets be taken with food. Food does not appear to affect GI absorption of the drug. Venlafaxine extended-release capsules should be administered as a single daily dose with food at approximately the same time each day (in the morning or evening). The extended-release capsules should be swallowed whole with fluid or the entire contents of a capsule(s) may be sprinkled on a small amount of applesauce immediately prior to administration. The extended-release capsules of venlafaxine and their contents should not be divided, crushed, chewed, or placed in water. If the capsule contents are administered by sprinkling on applesauce, the patient should drink some water after swallowing the entire mixture without chewing to ensure that the pellets are completely swallowed.

Risk of Sustained Hypertension

Venlafaxine therapy has been associated with sustained increases in blood pressure in some patients. An analysis of patients with sustained hypertension and patients whose hypertension resulted in discontinuance of the drug revealed that most blood pressure elevations were modest in severity (i.e., 10-15 or 8-28 mm Hg increases in supine diastolic blood pressure among patients receiving conventional or extended-release venlafaxine, respectively). However, sustained blood pressure increases of this magnitude could have adverse consequences in patients receiving the drug. In addition, some cases of elevated blood pressure requiring immediate treatment have been reported during postmarketing surveillance of the drug. Therefore, the manufacturer recommends that preexisting hypertension be controlled before initiating venlafaxine therapy and that regular blood pressure monitoring be performed in patients receiving the drug. In patients who experience a sustained increase in blood pressure during venlafaxine therapy, dosage reduction or discontinuance of the drug should be considered.

Risk of Serotonin Syndrome or Neuroleptic Malignant Syndrome (NMS)-like Reactions

Potentially life-threatening serotonin syndrome or neuroleptic malignant syndrome (NMS)-like reactions have been reported with selective serotonin- and norepinephrine-reuptake inhibitors (SNRIs), including venlafaxine, and selective serotonin-reuptake inhibitors (SSRIs) alone, but particularly with concurrent use of other serotonergic drugs (including serotonin [5-hydroxytryptamine; 5-HT] type 1 receptor agonists [''triptans''], drugs that impair the metabolism of serotonin [e.g., monoamine oxidase inhibitors], or antipsychotics or other dopamine antagonists). Manifestations of serotonin syndrome may include mental status changes (e.g., agitation, hallucinations, coma), autonomic instability (e.g., tachycardia, labile blood pressure, hyperthermia), neuromuscular aberrations (e.g., hyperreflexia, incoordination), and/or GI symptoms (e.g., nausea, vomiting, diarrhea). In its most severe form, serotonin syndrome may resemble NMS, which is characterized by hyperthermia, muscle rigidity, autonomic instability with possible rapid fluctuation in vital signs, and mental status changes. Patients receiving venlafaxine should be monitored for the development of serotonin syndrome or NMS-like signs and symptoms.

Serious (sometimes fatal) adverse reactions, possibly related to serotonin syndrome or NMS, have been reported in patients who received a monoamine oxidase (MAO) inhibitor shortly before or after venlafaxine therapy. Therefore, concomitant use of venlafaxine and MAO inhibitors is contraindicated. It is recommended that at least 2 weeks elapse between discontinuance of an MAO inhibitor and initiation of venlafaxine and that an interval of at least 1 week elapse between discontinuance of venlafaxine and initiation of an MAO inhibitor.

If concurrent therapy with venlafaxine and a 5-HT₁ receptor agonist (triptan) is clinically warranted, the patient should be observed carefully, particularly during initiation of therapy, when dosage is increased, or when another serotonergic agent is initiated. Concurrent use of venlafaxine and serotonin precursors (e.g., tryptophan) is not recommended.

If signs and symptoms of serotonin syndrome or NMS develop during venlafaxine therapy, treatment with venlafaxine and any concurrently administered serotonergic or antidopaminergic agents, including antipsychotic agents, should be discontinued immediately and supportive and symptomatic treatment should be initiated.

For additional information on serotonin syndrome,

Risk of Suicidality and Overdosage

Worsening of depression and/or the emergence of suicidal ideation and behavior (suicidality) or unusual changes in behavior may occur in both adult and pediatric (see Administration: Pediatric Precautions, in Dosage and Administration) patients with major depressive disorder or other psychiatric disorders, whether or not they are taking antidepressants. This risk may persist until clinically important remission occurs. Suicide is a known risk of depression and certain other psychiatric disorders, and these disorders themselves are the strongest predictors of suicide. However, there has been a long-standing concern that antidepressants may have a role in inducing worsening of depression and the emergence of suicidality in certain patients during the early phases of treatment. Pooled analyses of short-term, placebo-controlled studies of antidepressants (i.e., selective serotonin-reuptake inhibitors and other antidepressants) have shown an increased risk of suicidality in children, adolescents, and young adults (18-24 years of age) with major depressive disorder and other psychiatric disorders. An increased suicidality risk was not demonstrated with antidepressants compared with placebo in adults older than 24 years of age and a reduced risk was observed in adults 65 years of age or older. It is currently unknown whether the suicidality risk extends to longer-term use (i.e., beyond several months); however, there is substantial evidence from placebo-controlled maintenance trials in adults with major depressive disorder that antidepressants can delay the recurrence of depression.

The US Food and Drug Administration (FDA) recommends that all patients being treated with antidepressants for any indication be appropriately monitored and closely observed for clinical worsening, suicidality, and unusual changes in behavior, particularly during initiation of therapy (i.e., the first few months) and during periods of dosage adjustments. Families and caregivers of patients being treated with antidepressants for major depressive disorder or other indications, both psychiatric and nonpsychiatric, should be advised to monitor patients on a daily basis for the emergence of agitation, irritability, or unusual changes in behavior, as well as the emergence of suicidality, and to report such symptoms immediately to a health-care provider.

Although a causal relationship between the emergence of symptoms such as anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia, hypomania, and/or mania and either the worsening of depression and/or the emergence of suicidal impulses has not been established, there is concern that such symptoms may represent precursors to emerging suicidality. Consequently, consideration should be given to changing the therapeutic regimen or discontinuing therapy in patients whose depression is persistently worse or in patients experiencing emergent suicidality or symptoms that might be precursors to worsening depression or suicidality, particularly if such manifestations are severe, abrupt in onset, or were not part of the patient's presenting symptoms. If a decision is made to discontinue therapy, venlafaxine dosage should be tapered as rapidly as is feasible but with recognition of the risks of abrupt discontinuance.(See Discontinuance of Therapy under Dosage and Administration: Dosage.)

The results of retrospective studies indicate that venlafaxine overdosage may be associated with an increased risk of fatal outcome compared with that observed with SSRIs but lower than that associated with tricyclic antidepressants. Epidemiologic studies have shown that venlafaxine-treated patients have a higher preexisting burden of suicide risk factors than patients treated with SSRIs. The extent to which the finding of an increased risk of fatal outcomes can be attributed to the toxicity of venlafaxine in an overdosage as opposed to other characteristics of these venlafaxine-treated patients is not clear. As with other antidepressants, FDA and the manufacturer of venlafaxine recommend that the drug be prescribed in the smallest quantity consistent with good patient management, in order to reduce the risk of overdosage.

Risk of Bipolar Disorder

It is generally believed (though not established in controlled trials) that treating a major depressive episode with an antidepressant alone may increase the likelihood of precipitating a mixed or manic episode in patients at risk for bipolar disorder. Therefore, patients should be adequately screened for bipolar disorder prior to initiating treatment with an antidepressant; such screening should include a detailed psychiatric history (e.g., family history of suicide, bipolar disorder, and depression). Venlafaxine is not approved for use in treating bipolar depression.

Risk of Mydriasis

Mydriasis has been reported in association with venlafaxine therapy. Therefore, patients with elevated intraocular pressure or those at risk of angle-closure glaucoma should be monitored during treatment with the drug.

Pediatric Precautions

Safety and efficacy of venlafaxine in children younger than 18 years of age have not been established.

Although clinical studies designed to primarily assess the effect of venlafaxine on the growth, development, and maturation of children and adolescents have not been conducted to date, the results from available studies suggest that the drug may adversely affect weight, height, and appetite. Should the decision be made to prescribe venlafaxine for unlabeled (off-label) uses in pediatric patients, the manufacturer recommends regular monitoring of height and weight during therapy, particularly during long-term administration of the drug. In addition, the manufacturer states that the long-term safety of therapy with venlafaxine extended-release capsules (beyond 6 months) has not been systematically evaluated to date. Because the results of clinical studies indicate that the occurrence of blood pressure elevations considered to be clinically important in children and adolescents was similar to that observed in adults receiving venlafaxine, the manufacturer advises that the precautions for adults also should apply to pediatric patients receiving the drug.(See Risk of Sustained Hypertension under Dosage and Administration: Administration.)

In placebo-controlled clinical studies in children and adolescents 6-17 years of age, efficacy of venlafaxine (administered as extended-release capsules) was not established for major depressive disorder or generalized anxiety disorder, and there were increased reports of hostility and suicide-related adverse events such as suicidal ideation and self-harm. Hostility and suicidal ideation were the most common adverse effects leading to discontinuance of the drug in clinical studies in pediatric patients with major depressive disorder, each occurring in 2% of children and adolescents receiving venlafaxine extended-release capsules compared with less than 1 or 0% of those receiving placebo, respectively. In addition, abnormal/changed behavior was the most common adverse effect leading to discontinuance of the drug in clinical studies in pediatric patients with generalized anxiety disorder, occurring in 1% of children and adolescents receiving venlafaxine extended-release capsules compared with none of those receiving placebo. There were no suicides reported in any of these clinical studies.

FDA has determined that antidepressants increase the risk of suicidal thinking and behavior (suicidality) in children and adolescents with major depressive disorder and other psychiatric disorders. However, the FDA also states that depression and certain other psychiatric disorders are themselves associated with an increased risk of suicide. Anyone considering the use of venlafaxine in a child or adolescent for any clinical use must therefore balance the potential risks with the clinical need.(See Risk of Suicidality and Overdosage under Dosage and Administration: Administration.)

Dosage

Dosage of venlafaxine hydrochloride is expressed in terms of venlafaxine.

Although no overall differences in efficacy or safety were observed between geriatric and younger adults receiving venlafaxine, the possibility that some older patients may exhibit increased sensitivity to the drug cannot be ruled out. No age-related differences in the pharmacokinetics of venlafaxine have been identified and dosage adjustments are not necessary for geriatric patients on the basis of age alone; however, as with any drug used for the treatment of depression, generalized anxiety disorder, social phobia, or panic disorder, caution should be used when treating geriatric patients and dosage should be increased cautiously. In addition, the greater frequency of decreased hepatic and renal function observed in the elderly should be considered.(See Dosage and Administration: Dosage in Renal and Hepatic Impairment.)

Venlafaxine also should be used with caution in patients whose underlying medical condition might be compromised by increases in heart rate (e.g., patients with hyperthyroidism, heart failure, or recent myocardial infarction), particularly when the venlafaxine dosage exceeds 200 mg daily.

Patients should be monitored for possible worsening of depression, suicidality, or unusual changes in behavior, especially at the beginning of therapy or during periods of dosage adjustment.(See Risk of Suicidality and Overdosage under Dosage and Administration: Administration.)

Major Depressive Disorder

For the treatment of major depressive disorder in adults, the recommended initial dosage of venlafaxine is 75 mg daily administered in 2 or 3 divided doses as conventional tablets or as a single daily dose when using the extended-release capsules. According to the manufacturer, an initial dosage of 37.5 mg daily (as extended-release capsules) for the first 4-7 days (followed by an increase to 75 mg daily) may be considered for some patients. If no clinical improvement is apparent, the dosage may be increased by increments of up to 75 mg daily at intervals of not less than 4 days. If clinically necessary, dosage can be increased up to 225 mg daily in divided doses as conventional tablets or in a single daily dose when using the extended-release capsules. Although studies with venlafaxine conventional tablets in outpatient settings did not demonstrate additional benefit from dosages exceeding 225 mg daily in moderately depressed patients, patients with more severe depression responded to a mean dosage of 350 mg daily. Whether higher dosages of venlafaxine extended-release capsules are needed for more severely depressed patients is unknown; however, the manufacturer states that experience with dosages of venlafaxine extended-release capsules exceeding 225 mg daily is very limited. The manufacturer states that venlafaxine dosage should not exceed 375 mg daily (usually administered in 3 divided doses) as conventional tablets or 225 mg daily as extended-release capsules.

If desired, patients with depression who are undergoing treatment with a therapeutic dose of conventional tablets may be switched to the extended-release capsules at the nearest equivalent daily venlafaxine dose (e.g., change 37.5 mg twice daily administered as conventional tablets to a 75-mg extended-release capsule administered once daily).

Although the optimum duration of venlafaxine therapy has not been established, the manufacturer states that acute depressive episodes require several months or longer of sustained antidepressant therapy. Results of 2 relapse prevention trials indicate that the antidepressant efficacy of venlafaxine is maintained for up to 6 months in patients receiving 75-225 mg once daily as extended-release capsules and for up to 12 months in those receiving 100-200 mg daily in 2 divided doses as conventional tablets. In these studies, the same dosage of venlafaxine was used for both acute-phase and maintenance treatment. Based on these limited data, it is not known whether the dosage required to induce remission of depression would be comparable to that required to maintain euthymia. The usefulness of the drug in patients receiving prolonged therapy should be reevaluated periodically.

Generalized Anxiety Disorder

For the management of generalized anxiety disorder in adults, the initial dosage of venlafaxine as extended-release capsules recommended for most patients is 75 mg once daily. In some patients, it may be desirable to initiate therapy with a dosage of 37.5 mg daily given for the first 4-7 days, followed by an increase to 75 mg daily. Although a dose-response relationship for effectiveness in generalized anxiety disorder was not clearly established in clinical studies, certain patients not responding to a venlafaxine dosage of 75 mg daily may benefit from a higher dosage. Dosage in these patients may be increased in increments of up to 75 mg daily at intervals of not less than 4 days up to a maximum dosage of 225 mg daily.

The optimum duration of venlafaxine therapy for the management of generalized anxiety disorder has not been established. Although the drug has been used for up to 6 months in controlled clinical studies, the usefulness of the drug in patients receiving prolonged therapy should be reevaluated periodically.

Social Phobia

For the management of social phobia in adults, the recommended initial dosage of venlafaxine for most patients is 75 mg once daily as extended-release capsules. In some patients, it may be desirable to initiate therapy with a dosage of 37.5 mg daily given for the first 4-7 days, followed by an increase to 75 mg daily. Although a dose-response relationship for effectiveness in social phobia was not clearly established in clinical studies, certain patients not responding to a venlafaxine dosage of 75 mg daily may benefit from a higher dosage. Dosage in these patients may be increased in increments of up to 75 mg daily at intervals of not less than 4 days up to a maximum dosage of 225 mg daily.

The optimum duration of venlafaxine therapy for the management of social phobia has not been established. The efficacy of venlafaxine for long-term therapy (i.e., longer than 12 weeks) has not been demonstrated in controlled clinical studies to date. The usefulness of the drug in patients receiving prolonged therapy should be reevaluated periodically.

Panic Disorder

For the management of panic disorder in adults, the recommended initial dosage of venlafaxine is 37.5 mg once daily as extended-release capsules for 7 days, followed by 75 mg once daily as extended-release capsules for another 7 days. In clinical trials, 37.5 mg once daily was given initially for 7 days, then 75 mg once daily for 7 days; thereafter, dosage was increased in increments of 75 mg once daily every 7 days if necessary up to a maximum dosage of 225 mg daily. Although a dose-response relationship for effectiveness in panic disorder was not clearly established in fixed-dose clinical studies, certain patients not responding to a venlafaxine dosage of 75 mg daily may benefit from a higher dosage. Dosage in these patients may be increased in increments of up to 75 mg daily at intervals of not less than 7 days up to a maximum dosage of approximately 225 mg daily.

The optimum duration of venlafaxine therapy for the management of panic disorder has not been established. The efficacy of venlafaxine for long-term therapy (i.e., longer than 12 weeks) in prolonging time to relapse in responding patients has been demonstrated in a controlled clinical trial. However, the usefulness of the drug in patients receiving prolonged therapy should be reevaluated periodically.

Vasomotor Symptoms

Although the optimum dosage for the treatment of vasomotor symptoms in women with breast cancer and in postmenopausal women remains to be established, some clinicians suggest that venlafaxine be initiated at a dosage of 37.5 mg once daily as extended-release capsules, increasing as necessary to 75 mg once daily. In one clinical study, 75 mg once daily as extended-release capsules appeared to be optimal. Further increases in dosage do not appear to provide substantially increased benefit but are potentially more toxic.

Discontinuance of Therapy

Because withdrawal effects may occur, abrupt discontinuance of venlafaxine should be avoided. When venlafaxine therapy is discontinued, dosage should be tapered gradually and the patient carefully monitored to reduce the risk of withdrawal symptoms. If intolerable symptoms occur following dosage reduction or upon discontinuance of treatment, venlafaxine therapy may be reinstituted at the previously prescribed dosage until such symptoms abate. Clinicians may resume dosage reductions at that time but at a more gradual rate.

Withdrawal symptoms reported in clinical studies in adults receiving venlafaxine for major depression or generalized anxiety disorder include agitation, anorexia, anxiety, confusion, impaired coordination, diarrhea, dizziness, dry mouth, dysphoric mood, fasciculation, fatigue, headaches, hypomania, insomnia, nausea, nervousness, nightmares, sensory disturbances (including shock-like electrical sensations), somnolence, sweating, tremor, vertigo, and vomiting. Abrupt discontinuance or dosage reduction of venlafaxine has been associated with the appearance of new symptoms, the frequency of which increased with increased dosage and longer duration of treatment.

In clinical studies, venlafaxine hydrochloride extended-release capsules were discontinued by reducing the daily dosage by 75 mg at intervals of 1 week; however, individualized tapering may be necessary.

Dosage in Renal and Hepatic Impairment

Since clearance of venlafaxine is decreased and elimination half-life is increased in patients with renal impairment, the manufacturer states that dosage of the drug should be reduced by 25-50% in patients with mild-to-moderate renal impairment and by 50% in those undergoing hemodialysis and administration of the dose withheld until the dialysis period is complete (4 hours). Venlafaxine dosage also should be reduced by 50% in patients with moderate hepatic impairment. The manufacturer's labeling should be consulted for more detailed information on the dosage modifications in these patient populations.

Treatment of Pregnant Women during the Third Trimester

Some neonates exposed to venlafaxine, other selective serotonin- and norepinephrine-reuptake inhibitors (SNRIs), or selective serotonin-reuptake inhibitors late in the third trimester of pregnancy have developed complications, which have sometimes been severe and required prolonged hospitalization, respiratory support, enteral nutrition, and other forms of supportive care in special care nurseries. Therefore, the clinician should carefully consider the potential risks and benefits of treating a pregnant woman with venlafaxine during the third trimester of pregnancy. In addition, consideration should be given to cautiously tapering venlafaxine therapy in the third trimester prior to delivery if the drug is administered during pregnancy.