Pharmacokinetics of high and moderate intravenous doses of methotrexate

The pharmacokinetic parameters of methotrexate in nine cancer patients receiving 250-2500 mg/day were investigated. Both elimination rate constants and half-lives were calculated using a two-compartmental open model. The plasma levels-time profiles revealed a biphasic response with a mean initial elimination half-life of 2.3 +/- 0.2 hours and a terminal elimination half-life of 32.2 +/- 7.2 hours.