The aim of this study was to examine the long-term efficacy and safety of a monotherapy with quetiapine or sodium valproate (VPA) in patients with rapid cycling bipolar disorder.

This open-label trial was conducted at three German centers. A sample of 38 remitted or partly remitted bipolar patients with rapid cycling (quetiapine n = 22; VPA n = 16) were treated with quetiapine or VPA (flexible-dose design) up to 12 months. Analyses were based on the ITT-LOCF principle.

41 % of the patients with quetiapine and 50 % with VPA completed the trial. According to the Clinical Global Impression Scale responder rates tended to be higher for quetiapine than for VPA: i.e. 43 % vs. 25 % (depression), 48 % vs. 36 % (mania), and 43 % vs. 19 % (improvement in both mania and depression). There were no differences found between the treatment groups evaluating the HRSD, MADRS and YMRS. In contrast, Life Chart Method data showed that patients being treated with quetiapine had significantly less depressive days than patients on VPA whilst they did not differ in the number of days with manic symptoms. The incidence of adverse events, especially of orthostatic dysregulation and sedation was higher in the quetiapine group.

Quetiapine may be more effective than VPA regarding depressive symptoms and as effective as VPA in the treatment of manic symptoms in the long-term treatment of rapid cycling bipolar disorder. The side effect profile of quetiapine tends to be less favorable than the one of VPA.