title: Comparison of the effect on intragastric pH of a single dose of omeprazole or rabeprazole: which is suitable for on-demand therapy?
abstract: OBJECTIVE
  An ideal medication for heartburn should have the rapid onset of action needed for on-demand treatment. However, assessment of the onset of action of proton pump inhibitors has been largely subjective. We compared the inhibitory effect on gastric acid secretion of a single oral dose of omeprazole with that of rabeprazole.
  
  
  METHODS
  Fourteen Helicobacter pylori-negative men participated in this randomized, double-masked, two-way cross-over study. Intragastric pH was monitored continuously for 6 h after a single, randomly assigned 20 mg oral dose of either omeprazole or rabeprazole. After a 7-day washout period, the other drug was administered. Each patient's S-mephenytoin 4'-hydroxylase (CYP2C19) genotype was determined by polymerase chain reaction-restriction fragment length polymorphism.
  
  
  RESULTS
  Intragastric pH and pH holding time did not differ between treatments when the data were analyzed for the whole group without stratifying for CYP2C19 status. In CYP2C19 homozygous and heterozygous extensive metabolizers (10 subjects), rabeprazole maintained the intragastric at pH > 3 and> 4 for longer than omeprazole during both the 5 and 6 h study periods, and the average pH during the 6 h study period was higher with rabeprazole than with omeprazole. In these extensive metabolizers, rabeprazole maintained the pH > 2,> 3,> 3.5 and> 4 for longer during the 6 h study period than did omeprazole.
  
  
  CONCLUSIONS
  In H. pylori-negative men who are CYP2C19 homozygous or heterozygous extensive metabolizers, the intragastric pH after a single dose of 20 mg rabeprazole is higher during first 5-6 h than that after a single dose of 20 mg omeprazole.
authors.affiliation: The Third Department of Internal Medicine, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan. inamorim@med.yokohama-cu.ac.jp
authors.forename: Masahiko
authors.initials: M
authors.lastname: Inamori
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Togawa
authors.forename: Kirokazu
authors.initials: K
authors.lastname: Takahashi
authors.forename: Masato
authors.initials: M
authors.lastname: Yoneda
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Fujisawa
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Iwasaki
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ozawa
authors.forename: Taisuke
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Kenichi
authors.initials: K
authors.lastname: Muramatsu
authors.forename: Gaku
authors.initials: G
authors.lastname: Chiguchi
authors.forename: Shuhei
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Harunobu
authors.initials: H
authors.lastname: Kawamura
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Abe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kirikoshi
authors.forename: Noritoshi
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakaguchi
authors.forename: Tomoo
authors.initials: T
authors.lastname: Takamura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakajima
authors.forename: Norio
authors.initials: N
authors.lastname: Ueno
authors.forename: Hisahiko
authors.initials: H
authors.lastname: Sekihara
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000328:Adult; D000897:Anti-Ulcer Agents / Q000008:administration & dosage*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics; D001562:Benzimidazoles / Q000008:administration & dosage*; D065731:Cytochrome P-450 CYP2C19; D004311:Double-Blind Method; D005745:Gastric Acidity Determination; D005753:Gastric Mucosa / Q000378:metabolism*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008297:Male; D006899:Mixed Function Oxygenases / Q000235:genetics; D009853:Omeprazole / Q000008:administration & dosage*; D064750:Rabeprazole; D013270:Stomach / Q000187:drug effects*
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000897:Anti-Ulcer Agents; D001562:Benzimidazoles; D064750:Rabeprazole; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D009853:Omeprazole