PLASMA HALF-LIFE AND URINARY-EXCRETION OF CYCLOPHOSPHAMIDE IN CHILDREN

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 64  (10-1) , 1061-1066
Abstract
The plasma half-life and urinary excretion of cyclophosphamide were determined in 13 children who had various malignancies and/or who were being prepared for bone marrow transplantation. Disappearance from the plasma following i.v. infusion over a 1-2 h period was 1st-order. Urinary excretion was maximal during the first 8 h after administration and was essentially complete in 24 h. The plasma half-life in children not receiving known inducers of hepatic microsomal mixed-function oxygenase activity or cyclophosphamide in the 3 wk period prior to each determination ranged from 145-390 min. These values are lower than those ordinarily found in adult patients. The fraction of the total dose excreted in the urine as the parent compound ranged from 4-27%. Repeated administration of cyclophosphamide at approximately 30-60 day intervals did not appear to alter its plasma half-life, but did appear to increase its urinary excretion. Daily administration of cyclophosphamide (.apprx. 50 mg/kg per day .times. 2 or 4) significantly decreased its plasma half-life and urinary excretion suggesting that it may reversibly induce its own metabolism.