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Does H2 receptor antagonist-resistant ulcer exist?--A review based on bioavailability in man
1Department of Preventive Medicine, Kyoto Prefectural University of Medicine, Japan.
Gastroenterologia Japonica
|June 1, 1992
Summary
The existence of H2 receptor antagonist-resistant ulcers is questionable. Differences in bioavailability and metabolism of H2 receptor antagonists like cimetidine, famotidine, and ranitidine may explain treatment variations.
Area of Science:
- Pharmacology
- Gastroenterology
Background:
- The term
- H2 receptor antagonist-resistant (H2RA-resistant) ulcer
- is increasingly used for ulcers unresponsive to H2 receptor antagonists (H2RAs).
- Some studies suggest increasing H2RA dosage or switching agents can cure these ulcers.
Purpose of the Study:
- To investigate the absorption and bioavailability of oral doses of three H2RAs in healthy volunteers.
- To identify factors contributing to variable H2RA treatment responses.
Main Methods:
- Study of oral absorption and bioavailability of cimetidine, famotidine, and ranitidine in healthy volunteers.
- Analysis of drug decomposition in gastric acid and first-pass metabolism.
Main Results:
- Significant differences in bioavailability were observed: cimetidine (80%), ranitidine (50%), and famotidine (39%).
- Famotidine showed significant decomposition in gastric acid (35.8%-57.8%).
- Ranitidine underwent substantial first-pass metabolism in the liver (approx. 50%).
Conclusions:
- Variable bioavailability and metabolism of H2RAs can impact treatment efficacy.
- Famotidine and ranitidine require careful administration in patients with slow gastric emptying and hepatic dysfunction, respectively.
- The existence of true H2RA-resistant ulcers may be premature to conclude, suggesting patient-specific H2RA selection is crucial.