The efficacy and tolerability of escitalopram in obsessive-compulsive disorder (OCD) were investigated in a 24-week, randomised, placebo-controlled, active-referenced, double blind study.

466 adults with OCD were randomised to escitalopram 10mg/day (N=116), escitalopram 20mg/day (N=116), paroxetine 40mg/day (N=119), or placebo (N=115) for 24 weeks. The pre-specified primary efficacy endpoint was the mean change in the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) total score from baseline to Week 12 based on the intent-to-treat population and last observation carried forward (LOCF) using analysis of variance (ANCOVA).

Escitalopram 20mg/day was superior to placebo on the primary endpoint. After 12 weeks, on the primary efficacy endpoint, there was a statistically significant difference from placebo for 20mg escitalopram and paroxetine. In the escitalopram 20mg/day group, the Y-BOCS total score was significantly lower than in the placebo group as early as Week 6. At Week 24, the proportion of remitters (Y-BOCS≤10, LOCF, pre-defined) was significantly greater (p<0.05) for 20mg escitalopram (41.2%) than placebo (27.4%), but not for 10mg escitalopram (36.6%) or paroxetine (37.9%). The response rate (≥25 decrease from baseline Y-BOCS, LOCF, pre-defined) was significantly greater than placebo (50.4%) for 20mg escitalopram (70.2%) and paroxetine (67.2%). Statistically significantly more patients withdrew from the placebo group (18%) due to lack of efficacy, than paroxetine (8%) or escitalopram 20mg/day groups (6%). More paroxetine-treated patients withdrew due to adverse events than escitalopram- or placebo-treated patients.

Escitalopram was efficacious and well tolerated in the treatment of OCD, with 20mg escitalopram showing statistically significant superiority at the primary efficacy endpoint.