Coating polymers for colon specific drug delivery: a comparative in vitro evaluation

Area of Science:

• Pharmaceutical Sciences
• Drug Delivery Systems
• Polymer Science

Background:

• The colon is a promising site for targeted drug delivery due to its physiological conditions.
• Developing colon-specific drug delivery systems requires polymers that resist degradation in the upper gastrointestinal tract.
• Conventional enteric coatings often exhibit variable performance, necessitating exploration of alternative materials.

Purpose of the Study:

• To compare the efficacy of various polymers, including Eudragit, cellulose acetate phthalate, shellac, and ethyl cellulose, for colon-specific drug delivery.
• To evaluate the influence of polymer type and coat thickness on drug release profiles.
• To identify an optimal formulation for targeted indomethacin delivery to the colon.

Main Methods:

• Lactose-based indomethacin tablets were prepared and coated with different polymers (Eudragit, cellulose acetate phthalate, shellac, ethyl cellulose) at varying thicknesses.
• Coated tablets were subjected to dissolution testing under simulated gastric and small intestinal fluid conditions.
• Drug release rates were analyzed to determine the performance of each polymer coating.

Main Results:

• Dissolution rates were significantly influenced by the type and concentration of the polymer used.
• Shellac demonstrated superior performance compared to other tested polymers.
• A 3% (m/m) shellac coating effectively retarded indomethacin release for 3-4 hours, simulating small intestinal transit time.

Conclusions:

• Shellac, at a 3% coating concentration, is a highly suitable material for colon-specific drug delivery.
• This formulation ensures minimal drug release in the stomach and small intestine, facilitating targeted release in the colon.
• The study highlights the potential of shellac as a reliable carrier for colon-targeted pharmaceuticals.