Weekly methotrexate-calcium leucovorin rescue: effect of alkalinization on nephrotoxicity; pharmacokinetics in the CNS; and use in CNS non-Hodgkin's lymphoma.

Urinary alkalinization with oral sodium bicarbonate has decreased the incidence of acute nephrotoxicity and subsequent myelotoxicity in 18 adults receiving high-dose methotrexate with calcium leucovorin rescue (MTX-LCV) weekly in doses of 1-7.5 g/m2. Close monitoring of 24-hour serum creatinine and MTX levels can predict patients at risk for serious toxicity. By a prompt (24-36 hours) increase in the LCV dose rate, hematologic and biochemical evidence of myelosuppression has been prevented. Kinetic parameters in serum and lumbar cerebrospinal fluid (CSF) were studied in two patients following iv injection of 3 and 7.5 g/m2 respectively. Lumbar CSF MTX concentrations greater than 1 muM are achieved. The half-life of MTX in the CSF (11.95 hours) is twice as long as the serum half-life. In the presence of carcinomatous meningitis, further delay in the clearance of MTX from the CSF was seen. With weekly MTX-LCV, there have been four objective responses in six patients with non-Hodgkin's lymphoma in CNS relapse, including complete regression in two. It is suggested that therapeutic concentrations can be achieved in the central nervous system following MTX-LCV.