Effect of oral nimodipine on platelet function.

BACKGROUND AND PURPOSE Nimodipine, a calcium antagonist, has been reported to have beneficial effects in acute ischemic infarction. Some calcium channel antagonists have antiplatelet effects. We investigated the effect of oral nimodipine on platelet function in healthy volunteers. METHODS Twelve healthy volunteers (6 men and 6 women, mean age 32.9 +/- 5.6 years) took 30 mg nimodipine every 6 hours for 24 hours, followed by a week with no medication, followed by 60 mg every 6 hours for 24 hours. Ex vivo platelet function was measured at baseline, 1 hour after the first dose at each dosage strength, and 1 hour after the last dose at each dosage. Platelet studies included aggregation and adenosine triphosphate release in response to collagen, epinephrine, and adenosine diphosphate; maximal rate of primary aggregation; threshold adenosine diphosphate concentration for second-phase aggregation; and thromboxane B2 release at threshold aggregation. The bleeding time was measured at baseline and after the last 60-mg dose of nimodipine. RESULTS No change in any platelet function study was seen with 30 mg nimodipine every 6 hours. Platelet function studies were also unchanged after 60 mg every 6 hours, except for a slight decrease in aggregation and adenosine triphosphate release in response to suprathreshold (10 microM) adenosine diphosphate (p = 0.001, Student's paired t test). There was no significant change in bleeding times. CONCLUSIONS Oral nimodipine has minimal antiplatelet activity in young, healthy subjects.