Background: Limited information is available regarding optimal dosing or long-term pharmacotherapy with serotonin reuptake inhibitors in obsessive-compulsive disorder. This study evaluated the acute safety and efficacy and long-term efficacy, safety, and impact on relapse prevention of paroxetine in obsessive-compulsive disorder.
Method: We enrolled 348 outpatients with DSM-III-R obsessive-compulsive disorder in phase 1, a 12-week randomized, double-blind, parallel study of fixed doses of paroxetine (20 mg/day, 40 mg/day, or 60 mg/day) and placebo. In phase 2, 263 phase 1 completers were enrolled in 6 months of flexibly dosed open-label paroxetine treatment. In phase 3, 105 responders to open-label paroxetine were randomized to 6-month double-blind, fixed-dose, parallel paroxetine/placebo treatment to evaluate long-term efficacy, safety, and impact on relapse prevention. The study was conducted from July 1991 to February 1994.
Results: Patients in phase 1 acute treatment receiving 40 mg/day or 60 mg/day of paroxetine improved significantly (p < .05) more than those receiving placebo; the mean reduction in Yale-Brown Obsessive-Compulsive Scale score was 25% on 40 mg/day of paroxetine and 29% on 60 mg/day compared with 13% on placebo. During phase 3, long-term treatment, a greater proportion of placebo- (59%) than paroxetine-treated (38%) patients relapsed. Paroxetine was well tolerated at all doses, with no significant increase in frequency of adverse events during long-term compared with short-term therapy. Greater adverse events in the placebo than in the paroxetine group in phase 3 probably represent a discontinuation effect.
Conclusion: Paroxetine doses of 40 mg/day and 60 mg/day (but not 20 mg/day) are effective in treating acute obsessive-compulsive disorder. Long-term treatment with paroxetine is effective and safe, decreases the rate of relapse, and lengthens the time to relapse.