The metabolism of phenytoin by isolated hepatocytes and hepatic microsomes from male rats

M. Tsuru, R. R. Erickson, J. L. Holtzman

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Previous in vivo and in vitro studies have indicated that the K(m) for phenytoin hydroxylation is about 30 μM. Yet, the drug shows dose-dependent kinetics suggesting a K(m) of about 5 μM. The present studies indicate the discrepancy is not due to active transport of the drug in the hepatocyte or a decrease in the K(m) due to the low pO2 of the portal vein leading to uncompetitive inhibition. Studies in both hepatocytes and microsomes indicate the presence of a high affinity hydroxylase with a K(m) of 2 to 5 μM. These data suggest that this enzyme is the one primarily involved in the metabolism of phenytoin.

Original languageEnglish (US)
Pages (from-to)658-661
Number of pages4
JournalJournal of Pharmacology and Experimental Therapeutics
Volume222
Issue number3
StatePublished - Jan 1 1982
Externally publishedYes

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