Ticlopidine inhibition of phenytoin metabolism mediated by potent inhibition of CYP2C19.
Article Details
- CitationCopy to clipboard
Donahue SR, Flockhart DA, Abernethy DR, Ko JW
Ticlopidine inhibition of phenytoin metabolism mediated by potent inhibition of CYP2C19.
Clin Pharmacol Ther. 1997 Nov;62(5):572-7. doi: 10.1016/S0009-9236(97)90054-0.
- PubMed ID
- 9390115 [ View in PubMed]
- Abstract
A patient who had taken a stable dose of phenytoin for 2 years had a coronary stent placed for unstable angina and ticlopidine was added to his therapeutic regimen. Twenty-five days later, he was hospitalized with acute symptomatic phenytoin toxicity and a serum concentration of 46.5 micrograms/ml. Determination of metabolic genotype revealed that the patient had a wild-type genotype for CYP2C9, CYP2C19, and CYP2D6. Using human liver microsomes, we showed that ticlopidine is a potent inhibitor of cytochrome P450 2C19, with an estimated inhibition constant (Ki) of 3.7 +/- 0.2 mumol/L. The influence of ticlopidine on CYP2C9, the other cytochrome P450 isoform that metabolizes phenytoin, is relatively weak, with a calculated Ki of 38.8 +/- 27 mumol/L. These data suggest that, in this patient, phenytoin toxicity was caused by inhibition of CYP2C19 by ticlopidine, and the data emphasize the importance of CYP2C19 in the metabolism of phenytoin.
DrugBank Data that Cites this Article
- Drug Enzymes
Drug Enzyme Kind Organism Pharmacological Action Actions Ticlopidine Cytochrome P450 2C19 Protein Humans UnknownSubstrateInhibitorDetails Ticlopidine Cytochrome P450 2C9 Protein Humans UnknownInhibitorDetails - Drug Interactions
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