Efficacy and safety of fluoxetine in treating bipolar II major depressive episode.

As many as 45% of patients with major depressive episode also meet DSM-IV criteria for bipolar II (BP II) disorder. Although some clinicians advocate using a mood stabilizer in treating BP II depression, antidepressant monotherapy has been less well studied in this disorder. As part of a prospective, placebo-controlled, relapse-prevention study in 839 patients, the efficacy and safety of short- and long-term fluoxetine treatment in patients with BP II major depression compared with patients with unipolar (UP) major depression was retrospectively examined. Eighty-nine BP II patients (mean age, 41+/-11 years) were compared with 89 age- and gender-matched UP patients and with 661 unmatched UP patients (mean age, 39+/-11 years). All received short-term fluoxetine therapy at 20 mg daily for up to 12 weeks. Complete remission was defined as a final Hamilton Rating Scale for Depression score < or = 7 by week 9 that was then maintained for 3 additional weeks. Remitted patients were then randomly assigned to receive double-blind treatment with one of the following: (1) fluoxetine 20 mg daily for 52 weeks; (2) fluoxetine for 38 weeks, then placebo for 14 weeks; (3) fluoxetine for 14 weeks, then placebo for 38 weeks; or (4) placebo for 52 weeks. Antidepressant efficacy was similar in BP and UP patients during short-term therapy. Discontinuation for lack of efficacy was lower in BP II (5%) than in UP (12%) patients (p = not significant [NS]), whereas dropouts for adverse events were similar in BP II (11%) and UP (9%) patients. During long-term relapse-prevention therapy, relapse rates were similar in BP II and UP patients (p = NS). During short-term fluoxetine therapy, three BP II (3.8%) versus no matched UP (p = NS) and 0.3% unmatched UP (p = 0.01) patients had a "manic switch." During long-term fluoxetine therapy, one (2%) BP II and three (1%) unmatched UP patients (one taking placebo) had a manic switch (p = NS). In conclusion, fluoxetine may be a safe and effective antidepressant monotherapy for the short-term treatment of BP II depression with a relatively low manic switch rate. Fluoxetine may also be effective in relapse-prevention therapy in patients with BP II disorder.