Pramipexole for bipolar II depression: a placebo-controlled proof of concept study

Background The original serotonergic and noradrenergic hypotheses do not fully account for the neurobiology of depression or mechanism of action of effective antidepressants. Research implicates a potential role of the dopaminergic system in the pathophysiology of bipolar disorder. The current study was undertaken as a proof of the concept that dopamine agonists will be effective in patients with bipolar II depression. Methods In a double-blind, placebo-controlled study, 21 patients with DSM-IV bipolar II disorder, depressive phase on therapeutic levels of lithium or valproate were randomly assigned to treatment with pramipexole (n = 10) or placebo (n = 11) for 6 weeks. Primary efficacy was assessed by the Montgomery-Asberg Depression Rating Scale. Results All subjects except for one in each group completed the study. The analysis of variance for total Montgomery-Asberg Depression Rating Scale scores showed a significant treatment effect. A therapeutic response (>50% decrease in Montgomery-Asberg Depression Rating Scale from baseline) occurred in 60% of patients taking pramipexole and 9% taking placebo (p = .02). One subject on pramipexole and two on placebo developed hypomanic symptoms. Conclusions The dopamine agonist pramipexole was found to have significant antidepressant effects in patients with bipolar II depression.