Cocaine-calcium channel antagonist interactions.

Diltiazem, a benzothiazepine calcium channel antagonist, was given to six healthy men as a single 60 mg oral dose 120 min before IV injection of cocaine (0.2 mg/kg) in a double-blind, placebo-controlled, two-session study. Diltiazem alone produced no significant effects. Cocaine increased blood pressure, heart rate, pupil size and subjective "high" ratings, and decreased skin temperature. Diltiazem pretreatment diminished the cocaine effect on skin temperature, but did not otherwise alter the response to cocaine. Calcium channel antagonists diminish the effects of cocaine in vitro and in animals. Dosage considerations may be critical because of the differential sensitivity of various tissues to calcium channel antagonists.