Comparative studies of quality and bioavailability of methotrexate in Thai patients with rheumatoid arthritis.

ABSTRACT

The bioavailability of the two generic methotrexate oral preparations (Emtrexate, Pharmachemie Company, Holland and Methotrexate Remedica, Remedica, Cyprus as the test preparations), were compared to the innovator (Methotrexate Lederle, Lederle, U.S.A. as the reference) in 10 patients with rheumatoid arthritis. A single 7.5 mg oral dose of each preparation was given to the subjects in a randomized, double-blind, three-period crossover design with a 1 week washout period. Serum methotrexate concentrations were determined by using Fluorescence Polarization Immunoassay (Abbott TDx). No significant differences in pharmacokinetic parameters (AUC, Cmax, and Tmax) were observed between the test and reference preparations. The mean and 90 per cent CI of the ratio Emtrexate/Methotrexate Lederle and Methotrexate Remedica/Methotrexate Lederle of the Cmax, AUC0-8, and AUC0-alpha were 0.93 (0.87-1.00), 0.9 (0.82-0.98), 0.88 (0.79-0.99) and 0.97 (0.93-1.02), 0.95 (0.90-0.99), 0.94 (0.86-1.02), respectively. These values were well within the acceptable bioequivalence range of 0.8-1.25. The mean and 90 per cent CI of Tmax difference between Emtrexate-Methotrexate Lederle and Methotrexate Remedica-Methotrexate Lederle also overlapped the stipulated bioequivalence range of the Tmax differences of +/- 0.25 hour. Thus, Emtrexate and Methotrexate Remedica were considered bioequivalent to the reference Methotrexate Lederle regarding the rate of absorption and the extent of absorption.