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 microg/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, monotherapy 40.5 days; P=0.742), but was significant for symptomatic relapse (combination therapy 163 days, monotherapy 42 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.