To determine methotrexate (MTX) concentrations in the synovial membrane (SM) and cortical and trabecular bone of rheumatoid arthritis (RA) patients.
Ten RA patients (9 women, 1 man; mean +/- SD age 49.2 +/- 10.6, mean disease duration 13.2 +/- 9.9 years) undergoing surgical procedures for rheumatoid articular lesions participated in this study. Mean +/- SD MTX treatment duration was 26.4 +/- 21.3 months. The day preceding surgery, 10 mg of MTX was administered intramuscularly. During surgery, a mean +/- SD of 19.7 +/- 2.6 hours after MTX administration, SM, bone fragments, and blood were collected simultaneously. MTX was assayed by fluorescence polarization immunoassay in plasma and tissues.
The mean +/- SD plasma concentration was 0.0252 +/- 0.01 nmoles/ml at the time of tissue sampling. The mean MTX concentration in SM was 0.285 +/- 0.159 nmoles/gm. The mean MTX concentrations in trabecular and cortical bone were 0.292 +/- 0.164 and 0.286 +/- 0.126 nmoles/gm, respectively.
After intramuscular administration, high MTX concentrations are found in SM and cortical and trabecular bone of RA patients.