Reduced pressor effect of angiotensin II and of noradrenaline in normal man following the oral administration of the calcium-antagonist nifedipine.

The pressor response to both angiotensin II (5, 10 and 20 ng kg-1 min-1) and to noradrenaline (50, 100 and 200 ng kg-1 min-1) was reduced (P less than 0.05 to less than 0.005) in six healthy male subjects following the administration of the calcium-antagonist nifedipine (10 mg p.o.). Nifedipine induced a rise in basal plasma noradrenaline concentrations but did not alter the plasma concentrations of adrenaline, dopamine, renin and aldosterone. A slight reduction in the angiotensin II induced rise of plasma aldosterone by nifedipine was observed after the administration of the largest dose of angiotensin II only (P less than 0.05). The reduced responsiveness towards pressor agents following oral nifedipine is in keeping with the known antihypertensive effect of calcium-antagonistic drugs and could provide a concept for the effectiveness of these drugs in hypertensive crisis.