S-Mephenytoin hydroxylation phenotypes in a Jordanian population

Hakam F. Hadidi, Yacoub M. Irshaid, Raymond L. Woosley, Jeffrey R. Idle, David A. Flockhart

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We tested the ability of 194 unrelated, healthy Jordanian volunteers to metabolize S-mephenytoin. Mephenytoin (100 mg) was coadministered with debrisoquin (10 mg) orally and urine was collected for 8 hours. Mephenytoin metabolism was tested according to three measures: the amount of 4-hydroxymephenytoin, the S R enantiomeric ratio, and the presence of a polar, acid-labile metabolite in urine collected for 8 hours after the dose. The S R ratio and the presence of the acid-labile metabolite were determined in the urine of 16 patients who had low amounts of 4-hydroxymephenytoin (log hydroxylation index ≥1). On examination of these three parameters of oxidation status, nine subjects were found to be poor metabolizers of mephenytoin by all three parameters. Thus 4.6% (95% confidence interval of 1.6% to 7.6%) of Jordanian subjects studied were poor metabolizers of mephenytoin. According to the Hardy-Weinberg Law, the frequency of the recessive autosomal gene controlling the poor metabolizer status of mephenytoin was predicted to be 0.215% (95% confidence interval of 0.146% to 0.283%). These results are on the same order of magnitude as those determined in European white populations and constitute the first report in Arab populations.

Original languageEnglish (US)
Pages (from-to)542-547
Number of pages6
JournalClinical Pharmacology and Therapeutics
Issue number5
StatePublished - Nov 1995

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)

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    Hadidi, H. F., Irshaid, Y. M., Woosley, R. L., Idle, J. R., & Flockhart, D. A. (1995). S-Mephenytoin hydroxylation phenotypes in a Jordanian population. Clinical Pharmacology and Therapeutics, 58(5), 542-547. https://doi.org/10.1016/0009-9236(95)90174-4