Interaction between frusemide and aspirin.

The effects of the combination of aspirin and frusemide were studied on salicylate excretion by aspirin and on the diuresis and excretion of K+ and Na+ by frusemide in normal human subjects. There was a paradoxical net reduction in the natriuresis induced by aspirin, from 29.4 +/- 3.57 m-equiv and frusemide from 31.9 +/- 1.27 to 23.7 +/- 1.56 m-equiv on combined administration. Frusemide caused a reduction of the kalliuretic effect induced by aspirin from 48.86 +/- 8.36 to 18.3 +/- 3.76 m-equiv. The amount of salicylate excreted over a 3-hr period gave increases of 9.6 and 12.0% when aspirin was administered before frusemide and vice versa, respectively, while there was a 30.4% reduction when administered concomitantly.