Effect of catecholamine depletion on lithium-induced long-term remission of bipolar disorder

Background: This study investigated the effects of catecholamine depletion with alpha-methylparatyrosine (AMPT) on mood indices in patients with bipolar disorder who were in long-term remission with lithium therapy. Methods: Eight subjects with DSM-IV bipolar disorder currently in remission for >3 months on lithium were included in the study. Subjects were given either AMPT or placebo, in a randomized double-blind manner, in two test sessions of 4 days each. Results: Subjects did not have any significant changes in mood during AMPT or placebo administration; however, 24-48 hours after the last active AMPT dose subjects had a transient relapse of hypomanic symptoms. Relapse of hypomanic symptoms did not correlate with increases in serum levels of homovanillic acid or 3-methoxy-4-hydroxyphenylglycol. Conclusions: These findings suggest that the mechanism of prevention of manic relapse by long-term lithium therapy may be dependent on stability of the catecholamine system.