Vilazodone

Vilazodone (marketed as Viibryd) is an SSRI antidepressant developed by Clinical Data for the treatment of major depressive disorder. The chemical compound was originally developed by Merck KGaA (Germany). By 2009 two phase III clinical trials with positive results had been completed. Vilazodone was approved by the FDA for use in the United States to treat major depressive disorder in 10 mg, 20 mg, and 40 mg doses on January 21, 2011.

Pharmacology
Vilazodone acts as a serotonin reuptake inhibitor (IC50 = 0.2 nM) and 5-HT1A receptor partial agonist (IC50 = 0.5 nM; IA = ~60-70%). It has negligible affinity for other serotonin receptors such as 5-HT1D, 5-HT2A, and 5-HT2C.

Partial agonism of the 5-HT1A receptor is a relatively novel mechanism of action and is also shared by the anxiolytic buspirone (Buspar), and the atypical antipsychotic / antidepressant aripiprazole (Abilify).

Efficacy and tolerability
According to an eight-week, randomized, double-blind, placebo-controlled trial, vilazodone was reported to elicit an antidepressant response after one week of treatment. After eight weeks, subjects assigned to vilazodone experienced a significantly higher response rate than the group given placebo. At a dose of 40 mg per day, it is considered to be well tolerated and reported adverse effects ranged from mild to moderate in intensity; side effects included diarrhea, nausea, and somnolence. Additionally, in contrast to other SSRIs currently on the market, clinical trials showed that vilazodone did not cause significant weight gain or  decreased sexual desire/function as with many other antidepressants, which often cause people to abandon their use.