Methotrexate pharmacokinetics in psoriatic patients developing hepatic fibrosis.

Methotrexate sodium is a well-established therapeutic agent for severe psoriasis, but its use may be associated with hepatic fibrosis. We studied the pharmacokinetics of oral and intramuscular methotrexate in two groups of patients--those who did and those who did not develop hepatic fibrosis while receiving methotrexate therapy. Our results showed no difference between the two groups for peak or 24-hour methotrexate concentrations; for area under the curve to 24, 144, and 24 to 144 hours; or in total-body methotrexate clearance. Measurement of methotrexate plasma levels after drug administration is therefore unlikely to help in identifying those patients at risk of developing fibrosis.