title: Gastric acidity and acid breakthrough with twice-daily omeprazole or lansoprazole.
abstract: BACKGROUND
  In patients with severe gastro-oesophageal reflux disease (GERD), proton pump inhibitors are being used increasingly in twice-daily regimens to improve control of gastric acidity. Few data exist to compare the ability of the most-often used proton pump inhibitors, omeprazole and lansoprazole, to control gastric acid at twice-daily dosage regimens. Nocturnal acid breakthrough, defined as gastric pH < 4.0 continuously for > 60 min, may compromise treatment goals in patients with GERD.
  
  
  OBJECTIVE
  To compare the effects of omeprazole 20 mg b.d. or lansoprazole 30 mg b.d. on gastric acidity and the relative ability of each dosage regimen to prevent acid breakthrough.
  
  
  METHODS
  In a crossover pharmacodynamic study, 20 healthy volunteers (10 male, 10 female, mean age 38 years) were given omeprazole 20 mg b.d. or lansoprazole 30 mg b.d. for 7 days each, in a randomized manner. Each dosage regimen was separated by a minimum 7-day period where no medication was administered. On day 7 of each regimen, 24-h intragastric pH-metry was performed. The percentage of time for which gastric pH was below 4.0 and 3.0, the occurrence of daytime and nocturnal acid breakthrough, and the duration of action of each regimen were compared. Non-parametric statistics for paired data were used.
  
  
  RESULTS
  The percentage time for which gastric pH was below 4.0 was significantly lower with omeprazole 20 mg b.d. (median 14.8%) than with lansoprazole 30 mg b. d. (median 24.2; P=0.0372). Fourteen subjects showed more effective acid control when taking omeprazole; these were significantly more often H. pylori-negative patients compared with those for whom acid control was better on lansoprazole (P < 0.001). Nocturnal acid breakthrough occurred in seven patients (35%) on omeprazole and in 10 (50%) on lansoprazole (N.S.).
  
  
  CONCLUSIONS
  In healthy volunteers, twice-daily dosing of omeprazole 20 mg b.d. appears to be significantly more effective than lansoprazole 30 mg b.d. in controlling gastric acidity. The clinical importance of such a difference remains to be defined in GERD patients.
authors.affiliation: Oesophageal Research Laboratory, Department of Medicine, The Graduate Hospital, Phiadelphia, Pennsylvania 19146, USA. pkatz19512@aol.com
authors.forename: P O
authors.initials: PO
authors.lastname: Katz
authors.forename: J G
authors.initials: JG
authors.lastname: Hatlebakk
authors.forename: D O
authors.initials: DO
authors.lastname: Castell
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000328:Adult; D000897:Anti-Ulcer Agents / Q000008:administration & dosage* / Q000494:pharmacology / Q000627:therapeutic use; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D004334:Drug Administration Schedule; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D005745:Gastric Acidity Determination; D005764:Gastroesophageal Reflux / Q000188:drug therapy* / Q000503:physiopathology; D006801:Humans; D064747:Lansoprazole; D008297:Male; D008875:Middle Aged; D009853:Omeprazole / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000897:Anti-Ulcer Agents; D064747:Lansoprazole; D009853:Omeprazole