SNRIs and You: Venlafaxine

By | February 3, 2012

Effexor was the first SNRI introduced into clinical practice in 1993.

The first drug that Melissa will discuss in her featured topic presentation prior to next Monday’s Schlesinger Pain Centers Support Group meeting is venlafaxine. It is very commonly prescribed by Dr. Schlesinger as well as other practitioners, due to its cost advantage when compared to other drugs in its class.

Venlafaxine is the first serotonin norepinephrine reuptake inhibitor (SNRI) introduced into clinical practice, as Effexor in 1993 by Wyeth. Its efficacy in treating depression is roughly equivalent to the tricyclic antidepressants and the selective serotonin reuptake inhibitors (SSRIs), but at least in comparison to the tricyclic antidepressants its side effect profile is better.

More interesting from our point of view is the increased efficacy of serotonin norepinephrine reuptake inhibitors (SNRIs) in treating chronic pain. While initially off label, it has subsequently been shown to treat diabetic neuropathy and fibromyalgia with an efficacy similar to duloxetine and to be effective in migraine prophylaxis. It has also been shown to decrease the severity of hot flashes in post-menopausal women and various forms of post-traumatic stress disorder.

Common side effects include sedation, memory impairment, nausea, dry mouth, constipation, dizziness, insomnia, sweating and sexual dysfunction. In general its side effect profile is similar to the SSRIs with a few interesting differences. Weight gain and decreased blood pressure are rare. In fact anorexia occurs in up to 11% of patients. Serotonin syndrome is rare but has been reported in patients taking as little as 37.5 mg per day. As a result MAO inhibitors are contraindicated and drugs such as dextromethorphan, tramadol, tapentadol, meperidine and even the triptans should be use with caution.

The elimination half-life of venlafaxine is relatively short at about 5 hours, so that the drug must be taken at least three times per day to maintain reasonably constant blood levels, a disadvantage compared to other SNRIs. As with other antidepressants, the drug should be started and discontinued slowly to minimize side effects.

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