Lack of significant interaction between low dose methotrexate and ibuprofen or flurbiprofen in patients with arthritis.

Low dose methotrexate (MTX) is widely used in the treatment of rheumatoid arthritis. Current product recommendations accompanying MTX preparations advise against concurrent usage of nonsteroidal antiinflammatory drugs (NSAID), and adverse pharmacokinetic interactions have been reported with this combination. Six patients who were receiving MTX were studied with both oral and parenteral MTX, 10-25 mg/dose, without NSAID and with ibuprofen (2400 mg/day) and flurbiprofen (300 mg/day) for 6 weekly doses. Serum MTX levels were obtained at frequent intervals. Serum was separated and MTX analyzed using a radioimmunoassay (RIA). There was no observable interaction between MTX and either ibuprofen or flurbiprofen, with respect to the area under the curve per unit dose, Cmax, Cmax/dose, Tmax, and serum half-life. The pharmacokinetic indices were not significantly influenced by the route of administration.