Interactions of aspirin with nonsteroidal antiinflammatory drugs in man.

Healthy volunteers ingested fenoprofen and indomethacin, each alone or combined with aspirin. Concentrations in plasma of both fenoprofen and indomethacin were reduced significantly when administered with aspirin. Reduction of fenoprofen concentrations depended on the aspirin dosage and occurred whether fenoprofen was administered orally or intravenously. Fenoprofen did not affect plasma concentrations of salicylates. These results emphasize the need to assess carefully the effects of salicylates in comparative clinical trials of nonsteroidal antiinflammatory agents.