Verapamil: a new antimanic drug with potential interactions with lithium.

Verapamil is a calcium channel blocking agent with possible antimanic properties. In two elderly manic patients taking the medication in combination with lithium carbonate, profound bradycardia developed and was followed by a fatal myocardial infarction in one case. Clinical implications and possible mechanisms of cardiovascular interactions between verapamil and lithium are discussed. Caution is advised in the use of lithium and verapamil together.