Pilot investigation of isradipine in the treatment of bipolar depression motivated by genome-wide association

Objectives: Motivated by genetic association data implicating L-type calcium channels in bipolar disorder liability, we sought to estimate the tolerability, safety, and efficacy of isradipine in the adjunctive treatment of bipolar depression. Methods: A total of 12 patients with bipolar I or II depression entered this pilot, proof-of-concept eight-week investigation and 10 returned for at least one post-baseline visit. They were initiated on isradipine at 2.5 mg and titrated up to 10 mg daily, with blinded assessments of depression using the Montgomery-Åsberg Depression Rating Scale (MADRS) as well as adverse effects. Results: Among the 10 patients, three had bipolar II disorder; all but two reported current episode duration longer than six months. In all, four of 10 completed the study; no significant adverse events were observed, although one subject discontinued treatment per protocol because of possible hypomanic symptoms which had resolved prior to study visit. In a mixed-effects model, mean improvement in depression severity, assessed by MADRS, was 2.1 (standard error = 0.36) points/week (p < 0.001). Two of the 10 subjects remitted and four of the 10 subjects experienced 50% or greater symptomatic improvement with treatment. Conclusions: Isradipine merits further investigation for the treatment of bipolar depression. This preliminary trial illustrates the potential utility of genetic investigation in identifying psychiatric treatment targets.