Methotrexate concentrations in synovial membrane and trabecular and cortical bone in rheumatoid arthritis patients

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Abstract
Objective. To determine methotrexate (MTX) concentrations in the synovial membrane (SM) and cortical and trabecular bone of rheumatoid arthritis (RA) patients. Methods. 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. Results. 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. Conclusion. After intramuscular administration, high MTX concentrations are found in SM and cortical and trabecular bone of RA patients.