Diltiazem, a calcium antagonist, partly attenuates the effects of dextroamphetamine in healthy volunteers.

Calcium antagonists have previously been shown to be effective in the treatment of mania. In the present study we used dextroamphetamine administered to humans as a model of mania, to determine whether the calcium antagonist diltiazem would prevent dextroamphetamine-induced changes. This may help determine whether diltiazem is likely to be useful in the treatment of mania. Ten healthy volunteers were enrolled in this double-blind, placebo-controlled, balanced crossover study. Subjects received either oral diltiazem (60 mg) and placebo, placebo and dextroamphetamine (20 mg), diltiazem and dextroamphetamine, or placebo alone. Subjective and sleep changes were measured using visual analogue scales. Attentiveness and visual reaction times were measured repeatedly as were diastolic and systolic blood pressure. The results showed that dextroamphetamine alone produced a number of subjective changes, cardiovascular changes and changes in reaction time. Diltiazem significantly attenuated the cardiovascular changes, but not the subjective or reaction time changes. It is hypothesized that these findings may represent effects of diltiazem on noradrenergic neurotransmission. The results are tentatively supportive of suggestions that diltiazem may be clinically useful in the treatment of mania, as is another calcium channel antagonist, verapamil.