Effect of H2-receptor antagonists on bile acid metabolism

Several reports have been presented concerning pronounced overgrowth of bacteria in gastric juices of patients treated with H2-receptor antagonists. However, there has been no report concerning influence of H2-receptor antagonists on jejunal flora. Thus, to investigate the influence and its effect on bile acid metabolism, this study was performed: 1) to examine whether patients with gastric ulcers who have been treated with H2-receptor antagonists have positive bile acid breath tests due to bacterial overgrowth in their jejuna; 2) to verify that these bacteria, isolated and identified, have deconjugation ability; and 3) to determine whether the changes in the gastric pH are related to bacterial overgrowth.

The methods used were detection of deconjugation of bile acids in early phase by a bile acid breath test using 5 muCi of oral glycine-1-14C labeled glycocholate, aspiration of jejunal fluids by a double lumen tube with a rubber cover on the tip, and examination of deconjugation ability by thin layer chromatography.

Expired breath samples from all 18 patients after administration of H2-receptor antagonists showed a significant increase in 14CO2 specific activity compared with those before administration of H2-receptor antagonist and the normal controls, and bacterial overgrowth was found in the jejunal fluid of the patients after administration of H2-receptor antagonist. The administration of tetracycline to the 18 patients reduced the 14CO2 specific activity significantly. The following species were identified in the jejunal fluid samples obtained from the patients: Escherichia coli, Candida albicans, Pseudomonas aeruginosa, enterococcus, Lactobacillus bifidus, Bacteroides vulgatus, Bacteroides thetaiotaomicron, Bacteroides uniformis, Eubacterium lentum, and Eubacterium parvum. All of the species identified except for Escherichia coli, Pseudomonas aeruginosa, and Candida albicans deconjugated bile acids. There were significant correlations between the 14CO2 activity and gastric pH before and after administration of H2-receptor antagonist, respectively.

Patients with gastric ulcers who were treated with H2-receptor antagonists have increased bile acid deconjugation due to bacterial overgrowth in their jejuna containing species that can deconjugate bile acids. The bacterial overgrowth is probably associated with a shift to neutral pH in the gastric juice caused by the H2-receptor antagonists.