To investigate the pharmacokinetic interaction of oral meloxicam with intravenous (i.v.) methotrexate (MTX) in patients with rheumatoid arthritis (RA).

Thirteen patients with RA received MTX 15 mg i.v. in the absence of nonsteroidal antiinflammatory drugs (NSAID) and after one week in the presence of steady state levels of meloxicam. Plasma concentrations of MTX and meloxicam were determined using validated high performance liquid chromatography methods. One patient did not complete the study. The interaction of meloxicam and MTX was examined by equivalence testing. The endpoints AUCMTX, VssMTX, CltotMTX, and CmaxMTX were analyzed parametrically, whereas endpoints MRTMTX, CltotMTX, t1/2MTX, and tmaxMTX were analyzed nonparametrically.

The MTX plasma concentrations over time, with and without meloxicam, did not differ significantly. The point estimator for the ratio of log transformed data of the primary endpoint AUCMTX was 108%; the lower 95% confidence limit was 100% and the upper 95% confidence limit was 117%. Clinical laboratory values and adverse events revealed no increased MTX toxicity during concomitant treatment with meloxicam.

In this short term interaction study there was no statistically significantly effect of meloxicam on the pharmacokinetics of MTX. The combination of MTX and meloxicam did not lead to increased MTX toxicity.