[Acute natriuretic effect of nifedipine in elderly people with essential hypertension].

Following a two-week placebo period, a group of 10 elderly men (63-76 yrs) received a 20 mg nifedipine tablet each. Twelve hours later nifedipine, as compared to placebo, significantly raised diuresis, urine sodium excretion, and tubular sodium rejection, but had no affect GFR and urine potassium excretion. A significant drop in mean arterial pressure was registered six hours following nifedipine administration. After twelve hours, however, the statistical significance of the antihypertensive effect was reduced tenfold despite persisting natriuresis. In 4 elderly women (61-77 yrs), PRA level after nifedipine tended to rise, no such trend was observed for aldosterone. Although the mechanism of the natriuretic effect of Ca2+ channel blockers is not yet fully understood, it seems that the increase in Na+ excretion might be due to inhibition of Na+ reabsorption in renal tubules. It appears though as if the changes in Na+ excretion did not contribute to the acute BP decrease.