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Site-dependent small intestinal absorption of ranitidine
T Gramatté1, E el Desoky, U Klotz
1Institute of Clinical Pharmacology, Faculty of Medicine, Technical University, Dresden, Germany.
European Journal of Clinical Pharmacology
|January 1, 1994
Summary
Ranitidine absorption varies significantly along the small intestine, with highest rates in the upper regions. Secretion occurs in the mid-jejunum, impacting overall drug bioavailability.
Area of Science:
- Pharmacokinetics
- Gastroenterology
- Drug Absorption
Background:
- Understanding drug absorption is crucial for optimizing therapeutic efficacy.
- Ranitidine is a widely used medication, but its intestinal absorption characteristics require detailed investigation.
Purpose of the Study:
- To investigate the site-dependent absorption of ranitidine in the small intestine.
- To correlate intestinal absorption rates with serum concentrations and water flux.
Main Methods:
- Utilized the intestinal steady-state perfusion technique with triple-lumen tubing.
- Administered ranitidine (150 mg/L) at 10 mL/min for 180 min at various intestinal sites (65-250 cm).
- Simultaneously measured serum ranitidine concentrations and net intestinal water flux in 9 healthy male volunteers.
Main Results:
- Ranitidine absorption rates demonstrated significant site-dependence, peaking in the proximal duodenum/jejunum.
- The mid-jejunum exhibited marked ranitidine secretion into the gut lumen.
- Serum concentrations (AUC) decreased with more distal perfusion sites, confirming reduced absorption.
Conclusions:
- The small intestine exhibits a gradient of ranitidine absorption, with proximal regions showing higher uptake.
- Intestinal water flux positively correlated with ranitidine movement in proximal and distal sites, but not in the mid-jejunum.
- These findings highlight the importance of intestinal site in determining ranitidine bioavailability.