title: Role of omeprazole dosage and cytochrome P450 2C19 genotype in patients receiving omeprazole-amoxicillin dual therapy for Helicobacter pylori eradication.
abstract: OBJECTIVE
  To determine the factors that may influence Helicobacter pylori eradication in patients receiving omeprazole-amoxicillin dual therapy.
  
  
  METHODS
  Prospective, randomized study.
  
  
  METHODS
  University-affiliated hospital in Taiwan.
  
  
  METHODS
  A total of 128 adults (age range 20-75 yrs) with H. pylori-positive duodenal ulcer were enrolled; 121 completed the final evaluation.
  
  
  METHODS
  Patients were randomly assigned to one of four omeprazole-amoxicillin treatment groups, with each treatment administered for 2 weeks: O2A2 group (33 patients)--omeprazole 20 mg twice/day plus amoxicillin 500 mg 4 times/day; O2A1 group (32 patients)--omeprazole 20 mg twice/day plus amoxicillin 250 mg 4 times/day; O1A2 group (32 patients)--omeprazole 20 mg once/day plus amoxicillin 500 mg 4 times/day; and O1A1 group (31 patients)--omeprazole 20 mg once/day plus amoxicillin 250 mg 4 times/day.
  
  
  RESULTS
  Data were collected on H. pylori status, histologic parameters, antibiotic resistance, intragastric pH, cytochrome P450 (CYP) 2C19 genotype, and adverse reactions. The intent-to-treat cure rates (95% confidence interval [CI]) in groups O2A2, O2A1, O1A2, and O1A1 were 76% (95% CI 59-87%), 72% (95% CI 54-84%), 50% (95% CI 34-66%) and 52% (95% CI 35-68%), respectively. Eradication of H. pylori infection was statistically significantly dependent on omeprazole dosage, CYP2C19 genotype, age, gastritis status, and H. pylori density. All CYP2C19 poor metabolizers were cured, whereas the H. pylori cure rate in CYP2C19 extensive metabolizers varied from 44-76% in the different treatment groups. Eradication of H. pylori was favored in the omeprazole higher dose groups versus the lower dose groups (79% vs 53%, p=0.004). No secondary antibiotic resistance was found. Thirty-seven (95%) of 39 patients who failed with the initial treatment were cured by subsequent antibiotic susceptibility-driven proton pump inhibitor-based triple therapy.
  
  
  CONCLUSIONS
  Provided a maintenance dose of amoxicillin is given every 6 hours, eradication of H. pylori infection was significantly dependent on omeprazole dosage, CYP2C19 genotype, age, gastritis status, and H. pylori density.
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan.
authors.forename: Jyh-Chin
authors.initials: JC
authors.lastname: Yang
authors.forename: Hong-Long
authors.initials: HL
authors.lastname: Wang
authors.forename: Herng-Der
authors.initials: HD
authors.lastname: Chern
authors.forename: Chia-Tung
authors.initials: CT
authors.lastname: Shun
authors.forename: Bor-Ru
authors.initials: BR
authors.lastname: Lin
authors.forename: Chun-Jung
authors.initials: CJ
authors.lastname: Lin
authors.forename: Teh-Hong
authors.initials: TH
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000658:Amoxicillin / Q000008:administration & dosage / Q000627:therapeutic use*; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D000897:Anti-Ulcer Agents / Q000627:therapeutic use*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D065731:Cytochrome P-450 CYP2C19; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D004381:Duodenal Ulcer / Q000188:drug therapy / Q000235:genetics; D005260:Female; D005756:Gastritis / Q000188:drug therapy / Q000235:genetics; D005838:Genotype; D016481:Helicobacter Infections / Q000188:drug therapy* / Q000235:genetics / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009853:Omeprazole / Q000008:administration & dosage* / Q000627:therapeutic use; D054328:Proton Pump Inhibitors / Q000627:therapeutic use*; D012737:Sex Factors; D013624:Taiwan; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D000897:Anti-Ulcer Agents; D054328:Proton Pump Inhibitors; D000658:Amoxicillin; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D009853:Omeprazole