Venlafaxine chemical structureAn Effexor XR 75mg Capsule
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Venlafaxine

Venlafaxine hydrochloride is a synthetic derivative of phenethylamine and a prescription antidepressant first introduced by Wyeth in 1993, and marketed under the trade names Effexor® for tablets and Effexor XR® for extended-release capsules. Efexor® / Efectin® and Efexor XR® / Efexor® Depot / Efectin ER® are alternate trade name spellings used in some countries. Since venlafaxine is under patent, under current United States law, a generic will not be available to U.S. citizens until 2008. The European patent on the drug will hold until 2017. more...

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Uses

Venlafaxine is used primarily for the treatment of depression, generalized anxiety disorder, and social anxiety disorder in adults. It is known as one of the most activating of the newer antidepressants. While this can be helpful to some, as many depressed patients report feeling exhausted and unmotivated, to others it poses the risk of increased anxiety and agitation.

Venlafaxine is an effective antidepressant for many persons; however, it seems to be especially effective for those with treatment-resistant depression. Some of these persons have taken two or more antidepressants prior to venlafaxine with no relief. It has also been found to reduce the severity of 'hot-flashes' in menopausal women. In addition, a September 2004 Consumer Reports study ranked venlafaxine as the most effective among six commonly prescribed antidepressants. (However, this should not be considered a definitive finding, and responses to psychiatric medications vary significantly from individual to individual.)

Off-label / Investigational Uses

Substantial weight loss in patients with major depression, generalized anxiety disorder, and social phobia has been noted, but the manufacturer does not recommend the use as anorectical drug either alone or in combination with phentermine or other amphetamine-like drugs.

Description of Compound

The chemical structure of venlafaxine is designated (R/S)-1- cyclohexanol hydrochloride or (±)-1- cyclohexanol hydrochloride and it has the empirical formula of C17H27NO2 · HCl. It is a white to off-white crystalline solid, distributed in pentagon-shaped peach-colored tablets of 25 mg, 37.5 mg, 50 mg, 75 mg, and 100 mg. There is also an extended-release version distributed in capsules of 37.5 mg (gray/peach), 75 mg (peach), and 150 mg (brownish red).

Mechanism of Action

Venlafaxine is a bicyclic antidepressant, and is usually categorized as a serotonin-norepinephrine reuptake inhibitor, but it has been referred to as a serotonin-norepinephrine-dopamine reuptake inhibitor. It works by blocking the transporter "reuptake" proteins for key neurotransmitters affecting mood, thereby leaving more active in the synapse. At low dosages, venlafaxine blocks serotonin reuptake alone, similarly to a selective serotonin reuptake inhibitor (SSRI). At medium dosages (about 225mg/day), venlafaxine blocks the reuptake of norepinephrine as well as serotonin. At dosages above 300mg/day, it blocks dopamine reuptake in addition to serotonin and norepinephrine.

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Venlafaxine and Hot Flushes in Breast Cancer Survivors
From American Family Physician, 6/15/01 by Anne D. Walling

For several reasons, women may experience significant, even disabling, hot flushes following treatment for breast cancer. In addition to the induction of early menopause, treatment may involve therapy with tamoxifen, which has the specific side effect of inducing or exacerbating hot flushes. Most breast cancer survivors who are having hot flushes are not offered estrogen therapy to alleviate them because of concerns about potentiating recurrence of the breast cancer. Of the many agents investigated as potential alternatives to estrogen, the best evidence exists for progestins, but many patients and physicians are uncomfortable with any hormonal manipulation following breast cancer. Anecdotal evidence and the results of a small pilot trial indicate that the antidepressant venlafaxine relieves hot flushes. Loprinzi and colleagues studied the effect of venlafaxine on hot flushes in breast cancer survivors.

More than 200 women with troublesome hot flushes occurring more than 14 times per week and either a history of breast cancer or unwillingness to take hormonal therapy were recruited. Patients had to have a life expectancy of at least six months. Anti-estrogen therapies such as tamoxifen were allowed, but other therapies were excluded. After stratification for age, use of tamoxifen and symptom severity, the patients were randomly assigned to placebo or one of three treatment groups. The treatment groups included 37.5 mg, 75 mg or 150 mg dosages of venlafaxine daily. The two higher doses used weekly increments to achieve the full dosage level. The patients and study personnel were blinded as to treatment allocation. Patients completed daily diaries about symptoms, weekly questionnaires about quality of life and a Beck depression inventory. Each week, patients were contacted by a study nurse to measure blood pressure, encourage compliance and monitor symptoms, including potential side effects.

The four groups were similar across all variables, including age, tamoxifen use, duration of hot flushes and baseline depression scores. After four weeks, the median decrease in hot-flush scores was significantly greater in all three of the active treatment groups than in the placebo group. The median score reduction in the placebo group was 27 percent. The reduction in the venlafaxine-treated patients was 37 percent for the lowest dose and 61 percent for the two higher doses. Twenty percent of placebo patients reported a reduction of more than 50 percent in hot flushes compared with 45, 63 and 55 percent, respectively, for the three dosages of venlafaxine. In the placebo group, overall quality-of-life assessments decreased by three points in the placebo group but increased by three points in the venlafaxine group. Depression scores improved by an average of 1.6 points in the placebo group and by 2.4, 4.8 and 3.2 points, respectively, in the venlafaxine treatment groups. No significant differences were apparent for most side effects, but gastrointestinal symptoms were more common with the higher doses of venlafaxine.

The authors conclude that venlafaxine provides an effective treatment for hot flushes in women who are unwilling or unable to take estrogen. Balancing efficacy against side effects, they recommend 75 mg as the most appropriate dosage.

ANNE D. WALLING, M.D.

Loprinzi CL, et al. Venlafaxine in management of hot flashes in survivors of breast cancer: a randomised controlled trial. Lancet December 16, 2000;356:2059-63.

COPYRIGHT 2001 American Academy of Family Physicians
COPYRIGHT 2001 Gale Group

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