Acrylic polymers (e.g., Eudragit) can form coatings with diffusion- or dissolution-controlled release. Which polymer is an example of this class?

• A. Hydroxypropyl methylcellulose
• B. Eudragit
• C. Ethyl cellulose
• D. Karaya gum

Answer: (B)

Acrylic polymers like Eudragit are synthetic film-forming polymers based on methacrylate/acrylate units that can be used to coat a dosage form to control drug release. These coatings can work in two ways: they may dissolve at a specific pH to release the drug (dissolution-controlled) or remain as a semi-permeable barrier that the drug diffuses through (diffusion-controlled). Eudragit represents this versatile class because different grades are designed for either dissolution at certain pH values (enteric-type coatings) or for diffusion control through a permeable film. The other options are not acrylics: hydroxypropyl methylcellulose is a cellulose derivative used mainly as a hydrogel-forming matrix or film; ethyl cellulose is a cellulose derivative but not acrylic; Karaya gum is a natural gum. Therefore, the polymer that exemplifies this class is Eudragit.