To investigate the potential interaction of naproxen and methotrexate (MTX) in children with juvenile rheumatoid arthritis (JRA).
Nine children with JRA served as their own control taking their usual doses of MTX (0.22-1.02 mg/kg/week) and naproxen (14.6-18.8 mg/kg/day) separately and in combination.
MTX affected a > or = 30% change in naproxen kinetics in 6/8 patients, while naproxen altered MTX kinetics by > or = 30% in 4/9 patients.
MTX can alter nonsteroidal antiinflammatory drug (NSAID) kinetics in children with JRA and NSAID can alter MTX kinetics. NSAID toxicity should be considered when assessing adverse reactions in patients receiving the combination treatment of MTX and NSAID: