Clinical effects of intravenous nifedipine on renal function

Nifedipine, a calcium antagonist, was administered intravenously (13.3 micrograms/min) for 45 min, and the changes in blood pressure, glomerular filtration rate (GFR), renal blood flow (RBF), total renal resistance, urinary volume, urinary sodium and potassium excretion, plasma renin activity, and plasma aldosterone concentration were studied. GFR and RBF were measured by intravenous infusion of sodium thiosulfate and sodium para-aminohippurate, respectively. The subjects included 12 cases of essential hypertension, nine of chronic glomerular nephritis with hypertension, 14 of chronic glomerular nephritis without hypertension, and 12 normotensive controls. In patients with essential hypertension, GFR and RBF increased markedly (by 45.6% and 44.8%, respectively), but in normotensive and hypertensive patients with chronic glomerular nephritis, these indices did not change significantly. The urinary volume and urinary sodium excretion increased in all groups. The natriuresis induced by nifedipine is probably due to the increase of GFR and RBF. The results of this study suggest a difference in renal vascular pathophysiology between essential hypertension and chronic glomerular nephritis. The results also suggest a functional change of the renal vascular system in essential hypertension, i.e., the increased vascular tone and the particular sensitivity of renal arterioles to nifedipine.