title: Helicobacter pylori infection prevents the occurrence of the tolerance phenomenon of histamine H2 receptor antagonists.
abstract: BACKGROUND
  The attenuated anti-secretory activity of H2 receptor antagonists (H2RA) during continuous administration is referred to as the tolerance phenomenon. However, it is not clarified whether Helicobacter pylori infection affects the occurrence of tolerance to H2RA. It is also not clarified whether the tolerance phenomenon occurs to a new H2RA, lafutidine.
  
  
  OBJECTIVE
  To investigate the occurrence of the tolerance phenomenon in subjects with and without H. pylori infection during the continuous administration of lafutidine and famotidine.
  
  
  METHODS
  Subjects were 20 healthy male volunteers (seven H. pylori positive and 13 H. pylori negative cases). All subjects were examined by ambulatory intragastric pH monitoring five times without medication, on the first and 15th day of the administration of 20 mg b.d. famotidine and 10 mg b.d. lafutidine in a cross-over fashion.
  
  
  RESULTS
  The tolerance phenomenon was not observed in H. pylori-positive subjects during the 15-day-long administration of both H2RAs. In contrast, the tolerance phenomenon was observed in H. pylori negative subjects, which has been previously reported.
  
  
  CONCLUSIONS
  This study demonstrated that H. pylori infection affects the tolerance phenomenon during continuous administration of H2RAs.
authors.affiliation: Department of Gastroenterology and Hepatology, Shimane University, School of Medicine, Shimane, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Fujisawa
authors.forename: K
authors.initials: K
authors.lastname: Adachi
authors.forename: Y
authors.initials: Y
authors.lastname: Komazawa
authors.forename: T
authors.initials: T
authors.lastname: Mihara
authors.forename: T
authors.initials: T
authors.lastname: Azumi
authors.forename: T
authors.initials: T
authors.lastname: Katsube
authors.forename: K
authors.initials: K
authors.lastname: Furuta
authors.forename: H
authors.initials: H
authors.lastname: Kazumori
authors.forename: Y
authors.initials: Y
authors.lastname: Kinoshita
mesh_terms: D000081:Acetamides / Q000008:administration & dosage*; D000328:Adult; D000553:Ambulatory Care; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D003430:Cross-Sectional Studies; D004361:Drug Tolerance / Q000502:physiology*; D015738:Famotidine / Q000008:administration & dosage*; D016481:Helicobacter Infections / Q000503:physiopathology*; D016480:Helicobacter pylori; D006635:Histamine H2 Antagonists / Q000008:administration & dosage*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010880:Piperidines / Q000008:administration & dosage*; D011725:Pyridines / Q000008:administration & dosage*
chemical_list: D000081:Acetamides; D006635:Histamine H2 Antagonists; D010880:Piperidines; D011725:Pyridines; C076948:lafutidine; D015738:Famotidine