Ifosfamide pharmacokinetics

This review examines and details the pharmacokinetics of ifosfamide (a congener of cyclophosphamide) when administered by a number of commonly used chemotherapeutic regimes. The influence of route of administration, schedule of administration and dose on the pharmacokinetics of ifosfamide and its metabolites are discussed. Oral fractionated ifosfamide therapy, which causes an excessively high incidence of neurotoxicity, is similar to intravenous fractionated therapy in that it exhibits a time dependent increase in ifosfamide metabolic clearance. Five g/m2 ifosfamide given intravenously as a short (half hour) or long (24 hr) infusion does not exhibit dose dependent (zero-order) pharmacokinetics. In patients who develop ifosfamide/mesna associated CNS toxicity the pharmacokinetics of parent ifosfamide are not aberrant. This implies that ifosfamide metabolites are more likely to be responsible for the neurotoxicity rather than the parent drug. The development of simple and more specific analytical methodology, will allow further studies of the pharmacokinetics of the active ifosfamide metabolite(s). This may lead to further optimisation of the therapeutic index of ifosfamide treatment.