Asymptomatic tricyclic toxicity associated with diltiazem

Abstract

Therapeutic drug monitoring of tricyclic antidepressants is a controversial issue. A case is reported in which a patient with recurrent depression developed asymptomatic tricyclic toxicity while on trimipramine, a tricyclic antidepressant, and diltiazem, a calcium channel blocker. A metabolic interaction involving cytochrome P450 3A (CYP3A) is postulated. It is suggested that routine therapeutic drug monitoring of tricyclic levels should be an essential part of the management of depression.