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False negative urea breath tests with H2-receptor antagonists: interactions between Helicobacter pylori density and pH.
MedLine Citation:
PMID:  15156900     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: We studied the effects of famotidine, sodium bicarbonate, and citric acid on the 13C-urea breath test (UBT). METHODS: Helicobacter pylori-infected volunteers received a UBT, 40 mg of famotidine at bedtime, and a second UBT (pudding test meal, 648 mg NaHCO3 tablet then 125 mg of urea in 200 ml of water containing 650 mg of NaHCO3). Experiment 2 consisted of four UBTs. Two were standard citric acid UBTs with 75 mg of urea and 2 g citric acid and two were sequential bicarbonate-citric acid UBTs. Sequential UBTs consisted of administration of a 648 mg bicarbonate tablet with 50 g of Polycose in 200 ml of water. Five minutes later, 125 mg of 13C-urea was given in 75 ml of water containing 650 mg of NaHCO3. Breath samples were collected after 15 minutes. Then, to acutely acidify the stomach, 4 g of citric acid was given in 200 ml of water. A second breath sample was collected 15 minutes after the citric acid. The standard UBTs were done before and after 6 days of famotidine (40 mg b.i.d.). Sequential UBTs were done after 1 and 6 days of famotidine therapy. Gastric biopsies for histology, culture, and mucosal cytokines were assessed before and after 6 days of famotidine. RESULTS: Eighteen subjects participated, 10 in each experiment; seven had endoscopy with biopsy. Famotidine/ bicarbonate resulted an approximately 50% fall in UBT values (p = .021) with 10% becoming negative. The gastric pH increased from 5.1 +/- 0.5 to 6.7 +/- 0.2 (p = .03) although no pH value predicted the occurrence of false negative results. Under famotidine acid suppression, NaHCO3 reduced the delta over baseline (DOB) by 63% (p = .021). This was reversed with citric acid. Histology showed a H2-receptor antagonist-associated increase in the depth of gastric corpus inflammation. CONCLUSIONS: H2-receptor antagonists differ from proton pump inhibitors as high intragastric pH may cause a reduction in urease activity, unrelated to a reduced bacterial load and reversed by citric acid.
David Y Graham; Antone R Opekun; Medhavi Jogi; Yoshio Yamaoka; Hong Lu; Rita Reddy; Hala M T El-Zimaity
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Helicobacter     Volume:  9     ISSN:  1083-4389     ISO Abbreviation:  Helicobacter     Publication Date:  2004 Feb 
Date Detail:
Created Date:  2004-05-25     Completed Date:  2004-09-21     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9605411     Medline TA:  Helicobacter     Country:  United States    
Other Details:
Languages:  eng     Pagination:  17-27     Citation Subset:  IM    
Department of Medicine, Veterans Affairs Medical Center, Houston, TX 77030, USA.
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MeSH Terms
Breath Tests*
Citric Acid / administration & dosage
Endoscopy, Gastrointestinal
False Negative Reactions
Famotidine / administration & dosage,  pharmacology
Gastric Mucosa / microbiology,  pathology
Gastritis / microbiology,  pathology
Helicobacter Infections / diagnosis*,  microbiology,  pathology
Helicobacter pylori / growth & development*
Histamine H2 Antagonists / administration & dosage*,  pharmacology
Hydrogen-Ion Concentration
Middle Aged
Sodium Bicarbonate / administration & dosage
Urea / analysis*,  metabolism
Grant Support
Reg. No./Substance:
0/Histamine H2 Antagonists; 144-55-8/Sodium Bicarbonate; 57-13-6/Urea; 76824-35-6/Famotidine; 77-92-9/Citric Acid

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