Rapid versus non-rapid cycling as a predictor of response to olanzapine and divalproex sodium for bipolar mania and maintenance of remission: post hoc analyses of 47-week data.

BACKGROUND

Rapid cycling in bipolar disorder has been associated with greater morbidity. We examine whether rapid cycling affects treatment response to olanzapine or divalproex in acute mania.

METHODS

A post hoc analysis of a 47-week, randomized, double-blind study compared olanzapine (5-20 mg/day) to divalproex sodium (500-2500 mg/day) for bipolar manic or mixed episodes (N=251). Young Mania Rating Scale (YMRS) scores > or = 20 were required for inclusion. Patients were classified at study entry as "rapid cyclers" if they experienced > or = 4 episodes within the last year. A repeated measures analysis of variance was used to analyze YMRS change from baseline.

RESULTS

A significant three-way interaction (cycling frequency by medication by visit) was found when modeling change in YMRS total scores. For patients with bipolar I disorder identified as rapid cyclers, mania improvement across the trial did not differ significantly between treatment groups (p=0.181). Among non-rapid cyclers, olanzapine-treated patients had significantly greater YMRS improvement than divalproex-treated patients across the trial (p<0.001) and at most time points. Among olanzapine-treated patients, non-rapid cyclers experienced numerically greater YMRS improvement than rapid cyclers throughout the trial; statistically significant differences occurred at weeks 11, 15 and 39. In contrast, among divalproex-treated patients, YMRS scores were significantly better in rapid cyclers than non-rapid cyclers during the first two study weeks but were comparable thereafter. A similar pattern was seen in Clinical Global Impressions-Mania Severity scores. Hamilton Depression scores in rapid versus non-rapid cycling patients differed at some time points but not over the entire trial and differences by cycling status were not treatment-specific.

LIMITATIONS

Apart from the post hoc nature of the analyses, there were high dropout rates in both groups, and cycle frequency was not taken into account.

CONCLUSIONS

Rapid cycling patients did less well over long-term treatment than non-rapid cycling patients. Among rapid cycling patients, olanzapine and divalproex appear similarly effective against manic symptoms; however, among non-rapid cycling patients, olanzapine-treated patients experienced superior mania improvement. Olanzapine-treated, non-rapid cyclers experienced greater mania improvement than rapid cyclers. The converse was true of divalproex-treated patients early in treatment.