To compare the efficacy of escitalopram 10 or 20 mg/day with placebo in preventing relapse during 24 weeks in outpatients with obsessive-compulsive disorder (OCD) who had responded to an initial 16-week open-label treatment with escitalopram.

A multinational, randomised, double blind, placebo-controlled, flexible to fixed dose relapse prevention study with escitalopram in outpatients with OCD. The study consisted of a 16-week open-label period with 10 to 20 mg escitalopram followed by a 24 week double blind, placebo-controlled period, and a 1 week taper period. Patients who had responded to treatment (≥25% decrease in the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) total score) by the end of the 16-week open-label period were eligible for randomisation to either escitalopram or placebo for a further 24 weeks.

468 patients with OCD were treated with open-label escitalopram (10 mg or 20 mg) for 16 weeks. There were 320 responders (68%) who were randomised to change to placebo (n=157) or to continue with escitalopram (at the assigned dose) for further 24 weeks (n=163). The primary analysis (time to relapse) showed a clear beneficial effect of escitalopram relative to placebo (log-rank test, p<0.001). The proportion of patients who relapsed was statistically significantly higher in the placebo group (52%) than in the escitalopram group (23%) (p<0.001, chi-square test). The risk of relapse was 2.74 times higher for placebo- than for escitalopram-treated patients (chi-square test, p<0.001). Escitalopram was well tolerated.

Escitalopram was effective in preventing relapse of OCD and was well tolerated as continuation treatment.