Efficacy and Mood Conversion Rate of Short-Term Fluoxetine Monotherapy of Bipolar II Major Depressive Episode

Objective: As part of a long-term, relapse-prevention study of antidepressant versus mood stabilizer monotherapy of bipolar II major depressive episode, we prospectively examined the efficacy and mood conversion rate of initial fluoxetine monotherapy. We hypothesized that there would be a statistically significant reduction in depressive symptoms without a clinically meaningful increase in mood conversion symptoms. Methods: Patients received open-label fluoxetine monotherapy 10 to 80 mg daily for up to 14 weeks. Primary outcome was change over time in Hamilton Depression Rating score, with secondary outcomes including the proportion of treatment responders and remitters, change over time in Young Mania Rating Scale (YMRS) score, and frequency of mood conversion episodes. Results: One hundred forty-eight patients had at least 1 post-baseline measurement. Mean Hamilton Depression Rating score decreased by 9.0 points (P < 0.0005). There were 88 responder patients (59.5%; 95% confidence interval [CI], 51.1%-67.4%) (P < 0.0005) and 86 remitter patients (58.1%; 95% CI, 49.7%-66.2%) (P < 0.0005). Mean time to remission was 64.4 days (95% CI, 59.1-69.7 days). Six patients (4.1%; 95% CI, 1.5%-8.6%) (P < 0.0005) had hypomania, and 29 patients (19.6%; 95% CI, 13.5%-26.9%) (P < 0.0005) had subsyndromal hypomania, which did not result in treatment discontinuation. Six patients (4.1%; 95% CI, 1.5%-8.6%) had a YMRS score of 8 or greater (P < 0.0005), and 4 patients (2.7%; 95% CI, 0.7%-6.8%) (P < 0.0005) had a YMRS score of 12 or greater at any study visit. Conclusions: Although design limitations constrain the interpretation of the current findings, fluoxetine monotherapy may be an effective short-term treatment of bipolar II major depressive episode with a relatively low rate of syndromal hypomanic episodes.