Blood pressure, plasma renin activity and calcium metabolism in hypertensive pregnancy: the effect of nifedipine.

The effects of nifedipine on blood pressure, plasma renin activity and calcium metabolism were studied in nine hypertensive pregnant patients. Nifedipine (10 mg thrice daily per os) reduced blood pressure from 158/103 +/- 4/1 to 150/96 +/- 4/2 mmHg (mean +/- s.e.m.) during 4 to 5 days' treatment (p less than 0.05). The percentage change in diastolic blood pressure correlated negatively with the initial ambulatory (p less than 0.001) and rest (p less than 0.01) plasma renin activity and the initial daily urine calcium excretion (p less than 0.01). Calcium excretion in urine correlated positively with the initial ambulatory and rest plasma renin activity (p less than 0.01). The blood pressure reduction did not correlate with serum ionized, or total calcium, or the initial blood pressure. In six non-pregnant women, the rest plasma renin activity increased (p less than 0.05) after four days' administration of nifedipine. In the patients with hypertensive pregnancy, no changes in plasma renin activity were found during the treatment. The results indicated that the initial plasma renin activity, but neither the serum ionized calcium, nor the initial blood pressure, predicted the blood pressure-lowering effect of nifedipine in hypertensive pregnancy.