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Venlafaxine has been shown in clinical trials to be safe and well tolerated in patients with major depression. Data were pooled from 19 studies in which 2181 patients were given venlafaxine, 451 were given placebo and 591 were given a reference antidepressant (imipramine, trazodone, clomipramine, maprotiline, dothiepin or amineptine). Long-term safety was evaluated in 422 patients who were given venlafaxine for at least 1 year; as well, a total of 229 elderly patients have been treated with venlafaxine, including 66 who were given it for at least 1 year. The adverse events that occurred during short-term treatment in > or = 10% of patients were nausea, headache, insomnia, somnolence, dry mouth, dizziness, constipation, asthenia, sweating and nervousness. In comparator-controlled trials, the frequency of anticholinergic events with the reference agents was approximately twice that with venlafaxine. The safety profile and patient acceptability of venlafaxine are comparable to those of third-generation antidepressants, and possibly better than those of first-generation agents.
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PMID:Safety and tolerance profile of venlafaxine. 762 13

The pharmacology, pharmacokinetics, and clinical efficacy of venlafaxine hydrochloride, a new antidepressant, are described. Venlafaxine inhibits the reuptake of serotonin, norepinephrine, and, to a lesser extent, dopamine. In animal models, it does not significantly inhibit muscarinic, histaminic, or adrenergic receptor activity and does not inhibit monoamine oxidase. Venlafaxine is rapidly absorbed and metabolized in the liver to its active metabolite, O-desmethylvenlafaxine (ODV). Time to peak concentration is one to two hours for the parent compound and four to five hours for ODV. The pharmacokinetics of venlafaxine might be dose-dependent, although pharmacokinetic studies have had conflicting results. The major route of elimination is renal; thus, patients with renal dysfunction may require lower doses. In double-blind, placebo-controlled trials of venlafaxine for maintenance therapy, venlafaxine has shown effective antidepressant activity in severely ill patients with major depression. Antidepressant effectiveness may be apparent within two weeks; this finding needs to be replicated. The dosage is 75-375 mg/day administered in two or three divided doses. The strength of the antidepressant response may be correlated with increasing dosage. Nausea is the most commonly reported adverse drug reaction (ADR). Others include somnolence, dizziness, dry mouth, and sweating. All ADRs have commonly occurred at the beginning of therapy and decreased with time. Overall, venlafaxine is well tolerated. Venlafaxine is as effective as other available antidepressants. It may cause fewer anticholinergic, antihistaminic, and antiadrenergic ADRs and may have a quicker onset of therapeutic action than existing antidepressants.
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PMID:Venlafaxine: a heterocyclic antidepressant. 755 8

The antidepressant venlafaxine has a unique chemical structure and neuropharmacologic profile. It significantly inhibits reuptake of both serotonin and norepinephrine and lacks notable muscarinic-cholinergic or alpha-adrenergic effects. Premarketing studies involving more than 2000 patients showed the efficacy of venlafaxine to be significantly greater than placebo at dosages between 75 and 375 mg/day in both outpatients and inpatients. The medication may be administered twice or three times daily. Venlafaxine was found equally effective for patients older and younger than 60 years and in those with psychomotor retardation or agitation; it proved slightly more efficacious than fluoxetine in a comparison study with melancholic inpatients. A promising finding of these studies is the suggestion of a rapid onset of clinical effect for venlafaxine. In some studies, venlafaxine showed a consistent and robust clinical superiority over placebo by Week 1, and in the inpatient study involving melancholic patients, the superiority of venlafaxine was demonstrated as early as Day 4. In general, early responses are seen at the higher dosages. Venlafaxine has also shown promise in treating rigorously defined treatment-refractory depression. The adverse effects of venlafaxine that most often led to discontinuation from a clinical study were nausea (6%), somnolence (3%), insomnia (3%), and dizziness (3%). Although nausea was the most common adverse effect overall, it resolved rapidly--within the first 1 to 3 weeks of therapy. Other adverse events with incidences significantly higher than with placebo were dizziness, constipation, sweating, nervousness, and abnormal ejaculation. The seizure rate and potential for cardiac conduction changes or orthostatic hypotension with venlafaxine were comparable with rates seen with the serotonin selective reuptake inhibitors. A small number of patients experienced dose-dependent blood pressure elevation with venlafaxine in premarketing studies (3% to 5% of those receiving < or = 200 mg/day; 7% of those receiving 201-300 mg/day; 13% of those receiving > 300 mg/day vs. 2% receiving placebo). In general, venlafaxine is well tolerated, and its treatment discontinuation rate is similar to those of the newer antidepressants and superior to discontinuation rates with the first-generation agents.
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PMID:The role of venlafaxine in rational antidepressant therapy. 796 45

A double-blind, placebo-controlled trial was undertaken to compare the safety and efficacy of venlafaxine and trazodone in patients with major depression. Two hundred twenty-five patients entered an initial 6-week treatment phase, and 149 completed it. Ninety-six patients who were responders continued in a 1-year, double-blind, long-term phase during which they received the same medication and doses they had during the short-term phase. Both active treatments were significantly more effective than placebo on some measures during the short-term study, but venlafaxine produced more improvement in the cognitive disturbance and retardation factors on the Hamilton Rating Scale for Depression. Trazodone was more effective against the sleep disturbance factor. Patients on venlafaxine were most likely to enter the long-term phase and to remain in the trial longest. The side effect profiles of the three treatment groups were compared. Venlafaxine was most likely to cause nausea, whereas trazodone was associated with the most dizziness and somnolence.
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PMID:A comparison of venlafaxine, trazodone, and placebo in major depression. 819 64

Major depression is a debilitating disorder that is often undertreated. Psychotherapy, electroconvulsive therapy, and pharmacotherapy are options for management. Tricyclic antidepressants and selective serotonin reuptake inhibitors are the cornerstones of drug therapy. Venlafaxine, a phenylethylamine antidepressant that primarily inhibits reuptake of norepinephrine and serotonin, is an alternative to those agents. It has been studied in short-term and continuation studies and appears to have efficacy similar to that of imipramine, trazodone, and fluoxetine. Moreover, venlafaxine is effective in approximately one-third of patients with treatment-resistant depression. Venlafaxine is metabolized by the P-450 enzyme system to an active metabolite O-desmethyl-venlafaxine, which is excreted renally. Nausea, somnolence, and dizziness are dose-related adverse effects that often occur with initiation of therapy. Increases in blood pressure, particularly with high dosages, also may occur. Drug-drug interactions appear to be minimal.
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PMID:Therapeutic options for treating major depression, and the role of venlafaxine. 872 93

This 12-week, double-blind, placebo-controlled study evaluated the efficacy and safety of venlafaxine as first-line therapy for the treatment of major depression and major depression associated with anxiety in 384 adult outpatients. Fixed total daily dosages of 75, 150, and 200 mg of venlafaxine were administered in a twice-a-day regimen. Primary efficacy parameters were the Hamilton Rating Scale for Depression (HAM-D) total score, the HAM-D Depressed Mood Item, the Montgomery-Asberg Depression Rating Scale total score, and the Clinical Global Impressions Scale. Overall, a higher percentage of patients responded to venlafaxine than to placebo. Efficacy data indicated a dose-related response, most evident in the onset of clinical improvement; statistically significant improvements in some primary parameters were seen as early as 1 to 2 weeks after initiation of treatment, especially in the 150-and 200-mg/day groups. These dose-related clinical improvements continued through week 12. Venlafaxine-treated patients who had depression associated with anxiety showed significant dose-related improvements compared with placebo-treated patients; improvement was noted by scores on the HAM-D Anxiety-Psychic Item and Anxiety-Somatization Factor. Few clinically significant changes were observed in laboratory values, vital signs, or electrocardiogram tracings. Venlafaxine was generally well tolerated at all dosages. The most common study events included nausea, dizziness, somnolence, insomnia, dry mouth, and asthenia, which are consistent with findings of previous studies. The current study demonstrated that 75 to 200 mg/day of venlafaxine twice daily produced a dose-related improvement in the primary efficacy parameters and in the onset of significant antidepressant effects, which was noted at weeks 1 to 2 with the highest dosage tested (200 mg/day). The study also demonstrated that these dosages of venlafaxine were safe and effective as first-line therapy for major depression and depression associated with anxiety.
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PMID:The use of venlafaxine in the treatment of major depression and major depression associated with anxiety: a dose-response study. Venlafaxine Investigator Study Group. 947 38

(1) Generalised anxiety disorder is defined as excessive anxiety for at least 6 months. (2) Management is based primarily on psychological measures, with the aim of limiting recourse to drugs. The reference drugs are benzodiazepines. The treatment period should be as short as possible, to avoid adverse effects such as sedation and dependence. (3) Venlafaxine is a non tricyclic, non MAOI antidepressant. A sustained-release formulation has just been granted marketing authorisation in France for generalised anxiety disorder. (4) The clinical assessment file on venlafaxine in this indication includes results from two 8-week trials and a placebo-controlled trial with 6 months follow-up. The trials showed a significant improvement with venlafaxine on standard anxiety scales, but the clinical impact (at best moderate) has been poorly assessed. We found no comparison between venlafaxine and benzodiazepines. (5) In one trial venlafaxine was no more effective than buspirone. (6) The most frequent adverse effects of venlafaxine are gastrointestinal disorders, insomnia and dizziness. Venlafaxine carries a risk of drug interactions and withdrawal symptoms. (7) In practice, venlafaxine provides nothing new in the treatment of generalised anxiety disorder. The reference drug treatment remains a benzodiazepine.
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PMID:Venlafaxine and generalised anxiety disorder: new preparation. Minimise recourse to drugs. 1182 26

Venlafaxine is the first of a group of antidepressants that show dual reuptake inhibition of serotonin and noradrenaline (SNRIs). Originally marketed in an immediate release (IR) formulation a microencapsulated, extended release (XR) formulation is now available. Significant differences exist between these two formulations with respect to pharmacokinetic parameters which have an impact on clinical use. The XR has lower maximum plasma concentrations (Cmax) and achieves these at a later time (higher Tmax). The longer apparent elimination half-life of the drug after single XR doses suggests that it is suitable for once daily dosing compared with the twice daily dosing regimen required by the IR formulation. With respect to antidepressant efficacy the XR formulation is equivalent to other marketed antidepressants and to the IR formulation. Consistent with its pharmacokinetic properties the use of the XR formulation is associated with less nausea and dizziness at the initiation of therapy. While in clinical usage XR might be expected to increase compliance with medication and to reduce discontinuation syndromes there are few comparative studies for which this has been evaluated. The XR formulation of venlafaxine is no worse than the IR form with respect to tolerability and offers some benefits to patients in terms of ease of use. On the other hand there does not appear to be any increase in the efficacy of the active agent.
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PMID:The treatment of depression with different formulations of venlafaxine: a comparative analysis. 1471 6

Venlafaxine is a new antidepressant that inhibits the reuptake of both 5-hydroxytryptamine (serotonin; 5-HT) and noradrenaline (NA). It is somewhat more potent as an inhibitor of the reuptake of 5-HT than NA. Its potency to inhibit the reuptake of 5-HT is comparable to that of tricyclic antidepressants (TCAs) such as amitriptyline or imipramine, but it is less potent than these drugs at inhibiting the reuptake of NA. Consequently, at low doses, venlafaxine may be a more effective inhibitor of the reuptake of 5-HT than that of NA. The major metabolite of venlafaxine in humans, O-desmethylvenlafaxine, has comparable potency to the parent drug for inhibiting the reuptake of either NA or 5-HT in vitro, but it is less potent in vivo. Both venlafaxine and O-desmethylvenlafaxine are essentially devoid of activity at muscarinic cholinergic, H1 histaminergic, and 1-adrenoceptors. This probably accounts for venlafaxine having a side-effect profile similar to that of selective serotonin reuptake inhibitors (SSRIs) rather than that of TCAs. Venlafaxine is subject to extensive first-pass metabolism and is metabolised by the cytochrome P450 isoenzyme IID6 in the liver. The half-life of venlafaxine is 3-4 h and that of its principal metabolite is about 10 h. The daily dose of venlafaxine can be administered as either two or three divided doses without altering significantly the pharmacokinetics of venlafaxine. The most common side-effects of venlafaxine are nausea, sedation, dizziness, dry mouth and sweating, as well as sexual dysfunctions, primarily problems with erection and delayed ejaculation. In some patients, venlafaxine also causes sustained elevations in both systolic and diastolic blood pressure; this effect is dose-dependent. Venlafaxine is much safer in overdosage than the TCAs. Antidepressant efficacy of venlafaxine has been found both in out-patients and in-patients. In general, its efficacy is comparable to that of comparator drugs (primarily TCAs or SSRIs), and in some cases even greater, and its efficacy is greater than that measured with placebo.
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PMID:Venlafaxine:a novel antidepressant compound. 1598 62

Venlafaxine is a serotonin-noradrenaline reuptake inhibitor (SNRI) that has no affinity for muscarinic, adrenergic or histaminergic receptors. In short-term trials, the adverse effects that occurred more often with venlafaxine than with placebo included nausea, somnolence, dizziness, dry mouth, and sweating. Rapid titration of the dose of venlafaxine to higher levels appeared, not unexpectedly, to be associated with an increased incidence of side effects. Side effects that appeared to be dose related included insomnia, nausea and sexual dysfunction. The incidence of nausea and dizziness was highest during the first 2 or 3 weeks of therapy and decreased rapidly thereafter. Somnolence also decreased over time. At high doses blood pressure increases were reported in a small percent of patients on venlafaxine and antidepressant drugs but were uncommon at the venlafaxine dose of 75-150 mg daily. Studies with venlafaxine in healthy volunteers indicate a low potential for drug-drug interactions. Overdoses have been reported in 14 of 3,082 patients administered venlafaxine in clinical trials, and no deaths were reported among these patients. Overdoses of venlafaxine induced mainly drowsiness and lethargy.
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PMID:Neurobiologic basis of antidepressant safety profiles. 1969 84


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