Relapse prevention in bipolar I disorder: 18-month comparison of olanzapine plus mood stabiliser v. mood stabiliser alone

Background Few controlled studies have examined the use of atypical antipsychotic drugs for prevention of relapse in patients with bipolar I disorder. Aims To evaluate whether olanzapine plus either lithium or valproate reduces the rate of relapse, compared with lithium or valproate alone. Method Patients achieving syndromic remission after 6 weeks'treatment with olanzapine plus either lithium (0.6–1.2 mmol/l) or valproate (50–125 μg/ml) received lithium or valproate plus either olanzapine 5–20 mg/day (combination therapy) or placebo (monotherapy), and were followed in a double-masked trial for 18 months. Results The treatment difference in time to relapse into either mania or depression was not significant for syndromic relapse (median time to relapse: combination therapy 94 days, monotherapy40.5 days; P=0.742), but was significant for symptomatic relapse (combination therapy 163 days, monotherapy42 days; P=0.023). Conclusions Patients taking olanzapine added to lithium or valproate experienced sustained symptomatic remission, but not syndromic remission, for longer than those receiving lithium or valproate monotherapy.