Diuresis and natriuresis after dihydropyridines: role of prostaglandin E

It is known that calcium antagonists may produce a natriuresis and diuresis but the mechanisms are unknown and there have been few studies of the relative potencies of different drugs. This paper reports a study designed to measure the effect of nifedipine and nitrendipine on urine volume, sodium and potassium and the renal excretion of prostaglandin E2 (PGE2) in healthy, saline-loaded volunteers. Nifedipine and nitrendipine caused a significant natriuresis. Nifedipine also caused a significant diuresis but that produced by nitrendipine failed to reach statistical significance. Neither calcium antagonist altered PGE2 excretion. There was a small and insignificant fall in urinary potassium in all treatment groups. Blood pressure was not affected by the active treatments though heart rates tended to increase. We conclude that dihydropyridines have a potentially useful acute natriuretic effect which does not seem to be mediated by PGE2.