Effects of Calcium Antagonists on Renal Hemodynamics and Water and Sodium Excretion in Hypertensive Patients

Abstract

The new class of vasodilators, the calcium antagonists, differs from the previously available drugs, such as hydralazine, guancydine, and minoxidil, in that they do not cause sodium and water retention in acute and short-term usage. This is particularly evident during acute administration when both verapamil and nifedipine induce an increase in urinary sodium and urine volume in spite of the significant blood pressure reduction. The effect of calcium antagonists on sodium and water metabolism is due to a direct tubular action of these drugs and independent from the glomerular filtration rate and renal plasma flow, which are unmodified or only slightly increased. Finally, the natriuretic and diuretic effects of calcium antagonists during intravenous administration are evident at doses lower than those necessary to reduce elevated blood pressure. However, it appears also that by increasing the doses of felodipine, a dihydropyridine derivative, there is a decrease in glomerular filtration rate that can overwhelm the direct tubular action responsible for the diuretic and natriuretic effects.