Basic coating polymers for the colon-specific drug delivery in inflammatory bowel disease

Area of Science:

• Pharmaceutical Sciences
• Drug Delivery Systems
• Gastroenterology

Background:

• Inflammatory bowel disease (IBD) acute attacks cause significant colonic luminal pH decrease.
• This pH drop presents an opportunity for targeted drug delivery to the colon using acid-soluble coatings.
• Developing effective colon-specific dosage forms is key for topical IBD treatment.

Purpose of the Study:

• To evaluate the drug release characteristics of minitablets coated with acid-soluble polymers (Eudragit E, AEA).
• To investigate the influence of pH and hydrodynamic stress on drug release from these coated dosage forms.
• To assess the potential of these formulations for topical drug delivery in the colon.

Main Methods:

• Two minitablet formulations (conventional and swellable) were prepared by direct compression.
• Tablets were coated with varying amounts of Eudragit E or AEA.
• Dexamethasone release was measured spectrophotometrically across a pH range (2.0-6.8) and stirring rates (100-200 rpm).

Main Results:

• AEA coatings exhibited longer drug release lag times than Eudragit E due to slower dissolution and lower permeability.
• At low pH, drug release was stirring rate-dependent, linked to polymer film dissolution time.
• At pH 6.8, non-swelling Eudragit E tablet release was unaffected by hydrodynamic stress; AEA release depended on diffusion; swelling tablets showed no hydrodynamic stress effect.

Conclusions:

• Coating polymers like Eudragit E and AEA can modulate drug release for colon targeting.
• Formulation design (swellable vs. conventional) and coating properties significantly impact release kinetics.
• These findings support the development of pH-triggered, colon-specific drug delivery systems for IBD.