Antidepressant therapy with milnacipran and venlafaxine

Abstract

Specific serotonin norepinephrine reuptake inhibitors (SNRIs) have been described as "better tolerated tricyclic antidepressants" or as "boosted" selective serotonin reuptake inhibitors (SSRIs). Venlafaxine has become a therapeutic reference treatment for major depression. Although less widely studied, indirect comparisons with another SNRI, milnacipran, suggest an equivalent efficacy. This paper discusses these indirect comparisons and the recently published first double-blind, head-to-head comparison. Venlafaxine has potency at serotonin transporters which is about 30-fold greater than that at norepinephrine transporters while milnacipran has a similar potency at each transporter. Thus, at low doses, venlafaxine acts essentially as a SSRI, with significant noradrenergic activity only occurring at higher doses. To overcome the problem of the differing profile of venlafaxine at increasing doses, the first head-to-head study compared the therapeutic effects and tolerability of the two antidepressants when flexibly titrated to the high dose of 200 mg/day. The study showed that the two SNRIs have similar efficacy and safety profiles. Both drugs produced about 42% remissions at the end of the 20-week study. The most frequent adverse events in both groups were nausea, dizziness, headache, and sweating. Certain specific differences in tolerability are discussed.