Vilazodone hydrochloride (Viibryd): A selective serotonin reuptake inhibitor and partial 5HT1A receptor agonist for the treatment of major depressive disorder

The World Health Organization (WHO) estimates major depressive disorder (MDD) affects approximately 18 million Americans. Antidepressants became the fourth-largest prescribed drug class in 2009, with US prescription sales reaching $9.9 billion. On January 21, 2011, FDA approved vilazodone hydrochloride tablets for the treatment of MDD in adults.

Efficacy. Vilazodone's efficacy was established in two 8-week, multicenter, randomized, double-blind, placebo-controlled studies in adult patients who met the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for MDD (often characterized by depressed mood, loss of interest in once-pleasurable activities, significant changes in weight or appetite, insomnia or hypersomnia, psychomotor agitation, increased fatigue, feelings of guilt or worthlessness, slowed thinking or impaired concentration or suicidal ideations). Patients were titrated over 2 weeks to a dose of 40 mg of vilazodone (n=436) or placebo (n=433) once daily with food. In both trials, vilazodone was found to be superior to placebo in the improvement of depressive symptoms as measured by the mean change from baseline to week 8 in the Montgomery-Asberg Depression Rating Scale (MADRS) total score (-3.2, 95% CI, -5.2 to -1.3 and -2.5, 95% CI, -4.4 to -0.6).

Safety. In the same 2 randomized controlled trials noted above, 7.1% of patients receiving vilazodone discontinued treatment due to an adverse reaction compared to 3.2% of placebo-treated patients. The most common adverse reactions in vilazodone-treated patients (incidence ≥5% and at least twice the rate of placebo) included diarrhea (28%), nausea (23%), insomnia (6%), and vomiting (5%). As with other antidepressants, initial treatment with vilazodone may increase the risk of suicidal thinking and behavior in children, adolescents, and young adults aged 18 to 24 years. Similar to other SSRIs, patients taking vilazodone are at an increased risk of bleeding (particularly when used concomitantly with nonsteroidal anti-inflammatory drugs, aspirin, or other anticoagulants) and hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH). Other potential adverse effects associated with vilazodone include sexual dysfunction, seizures, serotonin syndrome, and neuroleptic malignant-like syndrome. Vilazodone had little effect on body weight.