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Drug interactions with diosmectite: a study using the artificial stomach-duodenum model.
N Castela-Papin1, S Cai, J Vatier
1Laboratoire de Pharmacie Clinique, Faculté de Pharmacie, 92296 Chatenay-Malabry, Paris, France.
International Journal of Pharmaceutics
|May 20, 1999
Summary
Diosmectite significantly interacts with various drugs, affecting their absorption. Drug ionization state is crucial for diosmectite interactions, impacting oral drug bioavailability.
Area of Science:
- Pharmacology
- Gastroenterology
- Materials Science
Background:
- Diosmectite is a natural clay used for its gastrointestinal protective properties.
- Understanding drug interactions with diosmectite is vital for optimizing oral drug therapy.
- Physicochemical properties of drugs influence their interaction with adsorbent materials.
Purpose of the Study:
- To investigate in vitro drug interactions with diosmectite.
- To determine how drug ionization state affects adsorption by diosmectite.
- To assess the impact of these interactions on drug absorption in the gastrointestinal tract.
Main Methods:
- Utilized an artificial stomach-duodenum model for in vitro studies.
- Monitored neutral and ionizable drugs (pKa 2-8) to characterize interactions.
- Quantified drug adsorption by diosmectite across different pH conditions.
Main Results:
- Neutral and acidic drugs showed moderate, pH-independent binding (<27%).
- Basic drugs (pKa<7) were strongly adsorbed in acidic conditions (>62%) but released in neutral conditions.
- Amphoteric and basic drugs (pKa≥7) exhibited high adsorption (>81%) in both gastric and duodenal simulations.
- Positively charged drugs showed significantly reduced absorption (>80%) in the distal duodenum model.
Conclusions:
- Drug ionization is a critical factor in diosmectite interactions.
- Diosmectite can significantly reduce the bioavailability of certain ionized drugs.
- These findings highlight the importance of considering drug ionization when co-administering with diosmectite.