title: Influence of CYP2C9 and CYP2C19 genetic polymorphisms on phenytoin-induced neurological toxicity in Indian epileptic patients.
abstract: OBJECTIVE
  Cytochrome P450 2C9 and 2C19 (CYP2C9 and CYP2C19, respectively) genetic polymorphisms play an important role in phenytoin (PHT) metabolism. We have evaluated whether these genetic polymorphisms have an effect on PHT-induced neurological toxicity in Tamilian (ethnic group native to southern India) patients with epilepsy.
  
  
  METHODS
  We studied 292 Tamilian patients who were taking PHT for the treatment of various epileptic seizures. PHT toxicity was defined on the basis of neurological signs of toxicity and further sub-classified into mild, moderate, and severe toxicity based on clinical severity. Genomic DNA was extracted from peripheral leukocytes and genotyped for CYP2C9*2, *3 and CYP2C19*2, *3 by PCR-restriction fragment length polymorphism analysis.
  
  
  RESULTS
  Of the 292 patients in the patient cohort, 58 were clinically diagnosed to have PHT toxicity. When risk ratios were calculated for each mutant CYP2C9 genotype separately, the adjusted odds ratio for CYP2C9*1/*3 was found to be 15.3 (95% confidence interval 5.8-40.3, P<0.0001) for the cases compared to controls. When the four single nucleotide polymorphisms of CYP2C9 and CYP2C19 were analyzed using a haplotype approach, significant difference in the distribution of the C-C-G-G haplotype was observed between the cases and controls.
  
  
  CONCLUSIONS
  Our results show that CYP2C9 genetic polymorphisms (particularly the *3 allele) were associated with high risk of epileptic patients developing PHT-induced neurological toxicity.
authors.affiliation: Department of Pharmacology, Center for Advance Research in Pharmacogenomics, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, 605006, India.
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Kesavan
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Narayan
authors.forename: Chandrasekaran
authors.initials: C
authors.lastname: Adithan
mesh_terms: D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D065731:Cytochrome P-450 CYP2C19; D065729:Cytochrome P-450 CYP2C9; D004827:Epilepsy / Q000188:drug therapy / Q000235:genetics*; D005260:Female; D006239:Haplotypes; D006801:Humans; D007194:India; D008297:Male; D020258:Neurotoxicity Syndromes / Q000235:genetics*; D010672:Phenytoin / Q000009:adverse effects* / Q000493:pharmacokinetics*; D020641:Polymorphism, Single Nucleotide
chemical_list: D010672:Phenytoin; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19
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