Abstract
Methotrexate (MTX) concentrations in serum and urine of a patient with osteogenic sarcoma were determined after four infusions of high-dose MTX, (200, 250, 300, 315 mg/kg) with a citrovorum factor rescue.
The peak serum MTX levels were attained during the 6-hour-period of infusion. After the infusion, serum levels showed the biphasic decline with the flection at 24-46 hours; their half-lives were 1.48-2.79 hours and 9.13-18.61 hours, respectively. Cumulative amounts of MTX excreted in urine during 82 hours were 50-60% of each dose. For each dose from 200 to 315mg/kg, the plots of urinary excretion rate were similar to the biphasic curve of the serum level. A good correlation was seen between the urinary excretion rate and the serum level, and its coefficient was 0.976 (n=38, P<0.005).
These results suggest that the data of the urinary excretion rate of MTX may be useful for prediction of the serum MTX level.
