OBJECTIVE: To determine the bioavailability of higher oral doses of methotrexate (MTX) in adult patients with rheumatoid arthritis (RA). METHODS: A pharmacokinetic analysis was performed in 15 patients with RA taking a stable dose of MTX (> or = 25 mg weekly). Separated by 2 weeks, a pharmacokinetic analysis was performed in each patient after oral and subcutaneous administration of the same dose of MTX. MTX serum concentrations were measured by a fluorescence polarization immunoassay. Pharmacokinetic analysis was performed with an iterative 2-stage Bayesian population procedure, obtaining population and individual pharmacokinetic parameters. RESULTS: The median MTX dose was 30 mg weekly (range 25-40 mg). A 2-compartment model best described the serum MTX concentration versus time curves. The mean bioavailability after oral MTX was 0.64 (range 0.21-0.96) compared to subcutaneous administration. There was a statistically significant difference in the bioavailability of the 2 administration regimens. CONCLUSION: Bioavailability of a higher oral dose of MTX in adult patients with RA is highly variable, and on average two-thirds that of the subcutaneous administration. To improve efficacy of MTX at dosages of 25 mg weekly or more, a change to parenteral administration should be considered.
OBJECTIVE: To determine the bioavailability of higher oral doses of methotrexate (MTX) in adult patients with rheumatoid arthritis (RA). METHODS: A pharmacokinetic analysis was performed in 15 patients with RA taking a stable dose of MTX (> or = 25 mg weekly). Separated by 2 weeks, a pharmacokinetic analysis was performed in each patient after oral and subcutaneous administration of the same dose of MTX. MTX serum concentrations were measured by a fluorescence polarization immunoassay. Pharmacokinetic analysis was performed with an iterative 2-stage Bayesian population procedure, obtaining population and individual pharmacokinetic parameters. RESULTS: The median MTX dose was 30 mg weekly (range 25-40 mg). A 2-compartment model best described the serum MTX concentration versus time curves. The mean bioavailability after oral MTX was 0.64 (range 0.21-0.96) compared to subcutaneous administration. There was a statistically significant difference in the bioavailability of the 2 administration regimens. CONCLUSION: Bioavailability of a higher oral dose of MTX in adult patients with RA is highly variable, and on average two-thirds that of the subcutaneous administration. To improve efficacy of MTX at dosages of 25 mg weekly or more, a change to parenteral administration should be considered.
Authors: Hamid J Mohamed; Michael J Sorich; Stefan M Kowalski; Ross McKinnon; Susanna M Proudman; Leslie Cleland; Michael D Wiese Journal: Eur J Clin Pharmacol Date: 2015-02-18 Impact factor: 2.953
Authors: Dong-Yang Liu; Hoi-Kei Lon; Yan-Lin Wang; Debra C DuBois; Richard R Almon; William J Jusko Journal: Biopharm Drug Dispos Date: 2013-04-07 Impact factor: 1.627
Authors: Julia Korell; Lisa K Stamp; Murray L Barclay; Judith M Dalrymple; Jill Drake; Mei Zhang; Stephen B Duffull Journal: Clin Pharmacokinet Date: 2013-06 Impact factor: 6.447