Risperidone adjunctive therapy duration in the maintenance treatment of bipolar I disorder: A post hoc analysis.

BACKGROUND: Risperidone, an atypical antipsychotic medication, is recommended as a first line treatment for acute mania in patients with bipolar disorder I (BD I). It is unknown if continuing treatment with risperidone adjunct to lithium or valproate after remission of the manic episode offers additional benefit in prevention of mood episode relapse.

METHODS: A post-hoc subgroup analysis was conducted using data from a 52-week, double-blind, placebo controlled trial involving 93 patients treated with oral risperidone adjunct to mood stabilizer, randomized to arms discontinuing risperidone at entry ("0-week arm"), 24 weeks after entry ("24-week arm") or continuing risperidone ("52-week arm"). Time to any episode, manic episode, and depressive episode was compared between arms using Cox regression models.

RESULTS: Time to any mood episode was longer in the 24-week arm versus the 0-week arm (HR: 0.57, 95% CI: 0.31-1.05, P = 0.07) and shorter in the 52-week arm versus 24-week arm (HR: 1.85, 95% CI: 1.00-3.41, P = 0.05), though these results were not significant. Time to relapse into manic episode was significantly longer in the 24-week arm versus 0-week arm (HR: 0.14, 95% CI: 0.03, 0.65, P = 0.01). No other significant differences were observed between arms.

LIMITATIONS: The sample size was modest, as the original dataset was powered to study optimal duration for two atypical antipsychotics.

CONCLUSIONS: Adjunctive risperidone treatment was observed to reduce the risk of manic episodes during the first 24 weeks, but not after 24 weeks. Treatment did not appear to reduce the risk of depressive episodes.