[Bolus and maintenance infusion of high-dose methotrexate]

For 17 patients with bone and soft tissue sarcoma, 32 bolus and maintenance infusions of high-dose methotrexate (MTX) were performed to induce rapid elevation of plasma MTX concentration and to maintain it. At the doses of 200-300 mg/kg, plasma MTX concentrations were measured by enzyme assay. It needed four hours to reach the steady state by five hours' constant rate infusion, with the plasma plateau concentration at about 1 X 10(-3) M/L. On the other hand, bolus infusion of MTX needed only one hour to reach over 5 X 10(-4) M/L, and the plateau concentration lasted during the maintenance infusion period. By the constant rate infusion as well as bolus infusion, it was possible to maintain the plasma concentration over 1 X 10(-4) M/L for 12 hours, but both infusions can not maintain 1 X 10(-3) M/L for a long time. From these results, clinical effects of high dose MTX against sarcomas seemed to be evaluated by the plasma MTX plateau concentration and the maintenance time.