title: CYP2C19 genotypes and omeprazole metabolism after single and repeated dosing when combined with clarithromycin.
abstract: OBJECTIVE
  Omeprazole is metabolized mainly by CYP2C19 which has two major mutations (CYP2C19*2 in exon5 and CYP2C19*3 in exon4) associated with the poor metabolizer (PM) phenotype. The aim of this study was to examine the relationship between genetic polymorphism of CYP2C19 and metabolism of omeprazole administrated as a single dose or as repeated-doses, which were in both cases co-administered with clarithromycin.
  
  
  METHODS
  Twelve healthy Japanese subjects were typed for CYP2C19 polymorphism. In the single-dose study, plasma levels of omeprazole and its metabolites were measured for 24 h after administration of 20 mg omeprazole and 400 mg clarithromycin to six healthy Japanese subjects. In the repeated-dose study, plasma levels of omeprazole and its metabolites were measured after repeated oral administration of 20 mg omeprazole and 400 mg clarithromycin twice daily for 6 days and then after 20 mg omeprazole and 400 mg clarithromycin once on the 7th day to the other 6 healthy Japanese subjects.
  
  
  RESULTS
  In the single-dose study, the areas under the plasma concentration-versus-time curve (AUCs) of omeprazole of homozygotes for the wild-type allele (*1/*1 n = 2), heterozygotes (n = 3) for the CYP2C19*2 (*1/ *2) or for the CYP2C19*3 (*1/*3) and heterozygote (n = 1) for the two defects (*2/*3) were on average 450, 1007 and 6710 ng x h(-1) x ml(-1), respectively. The ratios of AUCs of omeprazole/5-hydroxyomeprazole for *1/*1, *1/*2 or *1/*3 and *2/*3 were 1, 2 and 30, respectively. In the repeated-dose study, the AUCs of omeprazole for * 1/ *1, *1/*2 or *1/*3 and *2/*3 were 4041 (n = 2), 3149 (n = 3) and 6684 (n = 1) ng x h(-1) x ml(-1), respectively. The ratios of AUCs of omeprazole/5-hydroxyomeprazole for *1/*1, * 1/*2 or * 1/*3 and *2/*3 were7, 11 and 30, respectively. In the repeated-dose study, the AUC of omeprazole of * 1/*1 genotypes was nine-fold higher, that of *1/*2 and *1/*3 genotypes was three-fold higher, and the Cmax value of omeprazole was three-fold higher compared with subjects with the same genotype in the single-dose study. However, there were few differences in the AUC and Cmax of omeprazole between the *2/*3 genotype in the single-dose study and the homozygote for the CYP2C19*2 (*2/*2) in the repeated-dose study.
  
  
  CONCLUSIONS
  Subjects with *1/*1, *1/*2 and *1/*3 genotypes in the repeated-dose study had lower CYP2C19 activity than subjects of the same genotype in the single-dose study. The difference in omeprazole metabolism between subjects with different genotypes observed on day 1 seemed to disappear after 7 days of repeated-dose administration.
authors: Clinical Evaluation of Medicines and Therapeutics, Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.
authors: Q
authors: Q
authors: Zhou
authors: I
authors: I
authors: Yamamoto
authors: T
authors: T
authors: Fukuda
authors: M
authors: M
authors: Ohno
authors: A
authors: A
authors: Sumida
authors: J
authors: J
authors: Azuma
mesh_terms: D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases; D017291:Clarithromycin / Q000008:administration & dosage*; D065731:Cytochrome P-450 CYP2C19; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D005838:Genotype; D006801:Humans; D008297:Male; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009853:Omeprazole / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D011110:Polymorphism, Genetic / Q000235:genetics*; D011500:Protein Synthesis Inhibitors / Q000737:chemistry
chemical_list: D004791:Enzyme Inhibitors; D011500:Protein Synthesis Inhibitors; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D017291:Clarithromycin; D009853:Omeprazole