The effects of nifedipine and hydralazine induced hypotension on sympathetic activity

To determine whether inhibition of sympathetic activity is a factor in calcium antagonist induced hypotension, plasma noradrenaline was measured after intravenous infusion of hydralazine (25 mg) and the calcium antagonist nifedipine (4 mg) in 6 hypertensive males. The resultant reduction in mean blood pressure (12.4% and 14.2% respectively) was accompanied by similar increases in heart rate and plasma noradrenaline concentration. These results suggest that calcium slow channel blockade does not inhibit noradrenaline release from sympathetic nerves and that nifedipine induced hypotension is independent of such a mechanism.