Differential effects of two dihydropyridine calcium antagonists in humans

We studied the effects after single doses of niguldipine (0.3, 0.6, and 0.9 mg intravenously; 8 and 16 mg orally) and nifedipine (2 mg intravenously; 20 mg orally) in healthy male volunteers in randomized placebo-controlled experiments. Total peripheral resistance (TPR), heart rate-corrected electromechanical systole (QS2c), and preejection period (PEPc) were assessed noninvasively. Both drugs induced a similar pronounced decreased in TRP, indicating peripheral vasodilation, followed by increasing heart rate and cardiac output, a decrease in diastolic blood pressure, and a shortening of the PEPc. QS2c was unchanged after niguldipine. The prolongation of QS2c after oral nifedipine is suggestive of a negative inotropic effect. We conclude that the vasodilatory effects of dihydropyridines may (as for nifedipine) or may not (as for niguldipine) be associated with changes that are suggestive of negative inotropic effects, and that this difference is detectable by noninvasive methods in healthy subjects.