All subjects with observations available from the baseline and at least one post-baseline visit will be included in analyses. The primary outcome measure will be the change in YMRS scale scores from baseline to last observation. The difference in YMRS change between treatment groups will be tested for significance (alpha=0.05, two-tailed) using an independent-samples t-test. Measures of change in total affective burden, depressive and anxiety symptoms, global improvement, use of adjunctive anxiolytic and hypnotic medication, adherence to study medication, frequency and severity of side effects, and reasons for early termination will also be analyzed. The final dose achieved by each subject will be correlated with scale score change. Tolerability will be assessed based on adverse experiences, clinical laboratory tests, vital signs (blood pressure and pulse), weight, and discontinuation rates.