Influence of phenytoin on the disposition of irinotecan: A case report

Daryl J. Murry, Irene Cherrick, Veronia Salama, Stacey Berg, Mark Bernstein, Nancy Kuttesch, Susan M. Blaney

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

Irinotecan (CPT-11), a water-soluble topoisomerase I inhibitor, is metabolized by carboxylesterase enzymes to form an active metabolite, SN-38. Recent studies have shown that irinotecan also undergoes oxidative metabolism by the P450 isozyme CYP3A4, leading to the formation of a minor inactive metabolite, 7-ethyl-10-[4-N-[(5-aminopentanoic acid)-1-piperidino]-carbonyloxy-camptothecin (APC). The elucidation of this metabolic pathway suggests the potential for drug interactions when irinotecan is administered with other inducers or substrates of CYP3A4. In this report, the authors summarize the pharmacokinetic profile of irinotecan and its major metabolites with and without concomitant phenytoin administration in an individual patient. These studies revealed that concomitant phenytoin administration resulted in a marked decrease in the systemic exposure to irinotecan and SN-38 and an increase in the exposure to APC. The area under the curve of irinotecan and SN-38 decreased by 63% and 60%, respectively; the area under the curve of APC increased by approximately 16%. Further detailed pharmacokinetic studies of irinotecan in patients receiving concomitant therapy with enzyme-inducing anticonvulsants are required so that rational dosing recommendations can be provided for this patient population.

Original languageEnglish (US)
Pages (from-to)130-133
Number of pages4
JournalAmerican Journal of Pediatric Hematology/Oncology
Volume24
Issue number2
DOIs
Publication statusPublished - Jan 1 2002

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Keywords

  • CYP3A4
  • Irinotecan
  • Pharmacokinetics
  • Phenytoin
  • SN-38

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Hematology
  • Oncology

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