A Comparison of the Efficacy, Safety, and Tolerability of Divalproex Sodium and Olanzapine in the Treatment of Bipolar Disorder.

Background: This study compared the efficacy, safety, and tolerability of divalproex and olanzapine in the treatment of acute mania associated with bipolar disorder.

Method: This randomized, 12-week, double-blind, parallel-group, multicenter study included DSM-IV-defined bipolar disorder type I patients hospitalized for acute mania and randomly assigned to treatment with divalproex or olanzapine. After an inpatient period of up to 21 days, subjects were followed as outpatients. Dose adjustment was permitted during the inpatient period. Efficacy was assessed using change from baseline in Mania Rating Scale (MRS) score to day 21; other efficacy measures included the Brief Psychiatric Rating Scale, the Hamilton Rating Scale for Depression, and the Clinical Global Impressions-Part I, Severity of Illness scale. The primary safety endpoint was change from baseline in weight. Other safety and tolerability endpoints included spontaneous adverse event reporting and changes from baseline in laboratory measures and vital signs.

Results: 120 subjects (N=63 divalproex, N=57 olanzapine) were randomly assigned to treatment. No significant differences between groups were found for any efficacy variable for change from baseline to day 21. Mean MRS score changes from baseline to day 21 were -14.8 for divalproex and -17.2 for olanzapine (p=.210). A significantly (p<.05) greater proportion of olanzapine-treated subjects experienced somnolence, weight gain, edema, rhinitis, and speech disorder (slurred speech); no adverse events were significantly greater in the divalproex group. A number of laboratory measures also demonstrated significant treatment differences, but the clinical significance of many of these is uncertain. Mean body weight changes were significantly greater in the olanzapine group (+8.8 lb [+4.0 kg]) than the divalproex group (+5.5 lb [+2.5 kg], p<.050). One death occurred during the study (olanzapine group, diabetic ketoacidosis).

Conclusion: No significant difference in efficacy was found between treatment groups. Divalproex was associated with a more favorable adverse event profile and significantly less weight gain than olanzapine.