Diltiazem-induced psychosis and a possible diltiazem-lithium interaction.

Calcium channel blockers are being used increasingly for a variety of cardiovascular problems. Diltiazem hydrochloride, a benzothiazepine derivative, has been reported to have a low incidence of adverse side effects. We report a case of acute psychosis associated with the use of diltiazem in a patient receiving lithium carbonate therapy. Both diltiazem hydrochloride and lithium carbonate have calcium antagonist effects in the central nervous system, and we review their mechanisms of action. A possible synergistic drug interaction between diltiazem and lithium is reported.