What is the delayed release mechanism of enteric capsules?

Enteric capsules have attracted widespread attention in the field of drug delivery due to their unique design and delayed release mechanism. The capsules are designed to increase the bioavailability of the drug and reduce stomach discomfort by delaying the release of the drug, allowing it to bypass the acidic environment of the stomach and release it directly into the small intestine.

Enteric capsules are capsules that encapsulate drugs. Their design mainly includes two key components: a drug core and a delayed-release outer coating. The special design of this outer coating is central to achieving the delayed release mechanism.

The outer layer of enteric capsules is usually composed of one or more polymers, the most common being methyl methacrylate copolymer (Eudragit series) or hydroxypropyl methylcellulose. These materials are relatively insoluble in acidic environments but are soluble in alkaline environments.

In the stomach, the outer coating of enteric capsules remains relatively stable and will not be dissolved by the highly acidic environment. This property is achieved by selecting the appropriate polymer and controlling its formulation. Therefore, the capsule remains intact as it passes through the stomach, preventing premature release of the drug in stomach acid.

Once the enteric capsule crosses the stomach and enters the alkaline environment of the small intestine, the outer coating begins to dissolve. This is because in the alkaline environment of the small intestine, the selected polymer becomes water-soluble. As the outer layer dissolves, the drug core is exposed and begins to release the drug into the surrounding environment.

Another key advantage of the delayed release mechanism is targeted release in the small intestine. This means that the drug is released in specific areas of the small intestine, rather than evenly throughout the entire small intestine. Such precise release helps improve the bioavailability of the drug and ensures maximum efficacy in the target area.

Delayed release mechanisms also enable pharmaceutical scientists to control the release rate of drugs. This is crucial, especially for drugs that require a long period of action. By adjusting the properties of the outer coating, fast or slow release can be achieved to meet the needs of a specific drug.

The delayed release mechanism of enteric capsules is widely used in drug delivery, especially for those drugs that are sensitive to acidic environments, such as insulin, certain antibiotics, and biologics. This mechanism provides a safer and more effective delivery route for these drugs.