Oral Drug Delivery Systems: Delayed-Release Systems

Oral delayed-release systems are modified-release formulations that postpone drug release until reaching a specific site in the gastrointestinal tract, usually the intestine.

These systems address challenges such as gastric irritation and acid-induced drug degradation. Also, they contribute to achieving localized therapeutic action within the intestine.

They typically employ enteric coatings made of pH-sensitive polymers like cellulose acetate phthalate or methacrylic acid copolymers.

These coatings prevent drug dissolution in the stomach’s low pH and enable release in the higher intestinal pH, minimizing gastric side effects.

Some examples include enteric-coated aspirin and diclofenac.

Delayed release systems are often classified as intestinal or colonic release systems, depending on the target site within the gastrointestinal tract.

Some formulations—such as mesalamine—also act as targeted-release systems, releasing the drug in the terminal ileum and colon.