Ketoprofen-aspirin interactions.

To assess an interaction between ketoprofen and aspirin we gave both drugs orally, to steady state, to healthy men. Although ketoprofen did not alter salicylate absorption and disposition, we observed that concurrent administration of aspirin decreased ketoprofen protein binding and increased its plasma clearance. Salicylate also appeared to reduce metabolic ketoprofen conversion to conjugates and their renal elimination. The data suggested that salicylate also enhanced the metabolic conversion of ketoprofen to nonconjugate metabolites (p = 0.091). Our findings indicate that the drug-drug interaction between aspirin and ketoprofen is complex.