EntericCoated

Enteric coating refers to a polymer-based film applied to oral dosage forms to control where a drug is released in the gastrointestinal tract. Enteric-coated products are designed to resist dissolution in the acidic environment of the stomach and to dissolve once they reach the small intestine, where the pH is higher.

The primary purpose is to protect acid-sensitive drugs from gastric degradation, reduce gastric irritation or ulcer risk, and improve tolerability. Enteric coatings can also mask taste or odor and, in some cases, help target drug release to the proximal intestine or beyond. The coating remains intact in the stomach but dissolves in a more neutral to alkaline environment, allowing the active ingredient to release where it is better absorbed.

Coating materials are pH-sensitive polymers, including cellulose derivatives such as cellulose acetate phthalate and hydroxypropyl methylcellulose phthalate, and vinyl or acrylic polymers such as polyvinyl acetate phthalate and methacrylate copolymers (for example Eudragit L and Eudragit S). Eudragit L dissolves at approximately pH 6 or higher, while Eudragit S dissolves at around pH 7 or higher. Shellac and other natural or synthetic polymers are also used. The choice of polymer determines the disintegration pH and release profile.

Manufacture involves applying the coating as a thin, uniform film on tablets or pellets using pan coating or fluid-bed processes. Quality control includes measuring coating thickness and weight gain, and conducting disintegration tests in acidic media followed by dissolution tests in higher-pH buffers to ensure appropriate release.

Enteric coatings are widely used for drugs that irritate the stomach or are unstable in acid. Limitations include higher production costs, potential for incomplete coating, and factors such as alcohol exposure or crushing that can compromise integrity. Patients should swallow enteric-coated forms whole unless advised otherwise.