Therapeutic drug monitoring of tricyclic antidepressants is a controve
rsial issue, A case is reported in which a patient with recurrent depr
ession 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 postu
lated. It is suggested that routine therapeutic drug monitoring of tri
cyclic levels should be an essential part of the management of depress
ion.