Effect of indomethacin on salt and water homeostasis.

The effects of indomethacin-induced prostaglandin inhibition on sodium and chloride homeostasis in normal man were assessed. Seven normal subjects were on a 150-mEq sodium diet for 3 days prior to receiving indomethacin or no drug. Indomethacin decreased fractional excretions of sodium and chloride without affecting fractional excretion of potassium, creatinine clearance, or percent fractional reabsorption of free water. Cumulative sodium excretion at 8 hr fell from 49.8 +/- 7.2 to 16.1 +/- 4.8 mEq (p less than 0.005) after indomethacin. Chloride fell at 8 hr from 49.7 +/- 6.4 to 21.3 +/- 5.1 mEq (p less than 0.005). Urinary volume and osmolal clearance decreased in similar magnitudes such that free water reabsorption was not changed by indomethacin. This study showed that indomethacin decreased renal sodium and chloride excretion, implying that endogenous prostaglandins may be modulators of renal sodium excretion.