The effects of ibuprofen and indomethacin on renal function in the presence and absence of frusemide in healthy volunteers on a restricted sodium diet.

1. Since salt depletion stimulates the renal prostaglandin system to maintain renal function, the effects of indomethacin and ibuprofen upon renal haemodynamics, electrolyte excretion and renin release were examined in eight healthy male volunteers on a salt restricted diet, before and after frusemide administration. 2. Neither indomethacin (50 mg) nor ibuprofen (400 mg and 800 mg) affected renal blood flow, glomerular filtration rate or electrolyte excretion before frusemide. 3. Renal blood flow and glomerular filtration rate were significantly increased in the first 20 min after frusemide. These changes were significantly attenuated by indomethacin compared with placebo and ibuprofen 400 mg. Frusemide-induced diuresis but not natriuresis was inhibited by all treatments. 4. Both nonsteroidal agents inhibited equally the rise in renin activity seen after frusemide. 5. In this group of healthy volunteers on a salt restricted diet, ibuprofen and indomethacin had no detrimental effects on renal function in the absence of frusemide. The changes in renal haemodynamics due to frusemide were suppressed more by indomethacin than by ibuprofen, probably reflecting the more potent nature of indomethacin as an inhibitor of prostaglandin synthesis.