Objective: To evaluate the efficacy and tolerability of extended-release gepirone (gepirone-ER), a 5-HT(1A) agonist, versus placebo in the treatment of adult outpatients with major depressive disorder (MDD).

Method: A double-blind, randomized, placebo-controlled, parallel-group, 8-week study was conducted from October 2003 to August 2004 in outpatients 18 to 64 years old with moderate-to-severe MDD, as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR), and a baseline Hamilton Rating Scale for Depression (HAM-D(17)) total score > or = 20. Patients were titrated from 20 to 80 mg/day of gepirone-ER or placebo (most patients received gepirone-ER 60 or 80 mg/day by week 3). The primary outcome measure was baseline-to-endpoint mean change in HAM-D(17) total score. Secondary outcome measures included the 28-item version of the HAM-D, HAM-D depressed mood (item 1), Bech Six-Item Scale, Montgomery-Asberg Depression Rating Scale, and Clinical Global Impressions scale.

Results: Significantly greater reductions in HAM-D(17) total scores occurred in gepirone-ER-treated patients compared with placebo-treated patients by week 4 (p = .004) and continued through weeks 6 (p = .006) and 8 (p = .032). Secondary outcomes also improved significantly at multiple timepoints, including at endpoint. The most frequently reported adverse events in the gepirone-ER versus placebo groups were dizziness (45% vs. 10%), nausea (36% vs. 13%), and headache (24% vs. 16%). Dizziness occurred most frequently during initial dosing and up-titration.

Conclusions: Gepirone-ER significantly reduced depression symptoms and illness severity in MDD outpatients through the end of the study and was generally well tolerated, confirming previous findings.