Jun 14,2024

Enteric capsules are a drug delivery system designed to control drug release through the gastrointestinal tract. In the drug delivery process, controlling permeability is one of the key factors to ensure that the drug is released at a specific site.

1. The basic principle of enteric capsules:

Enteric capsules use a special polymer coating that is stable in an acidic environment and soluble in an alkaline environment. This means that enteric capsules can pass through the strong acid environment of the stomach without releasing drugs until they enter the alkaline environment of the small intestine and begin to dissolve and release drugs. This process ensures that the drug is not destroyed in the stomach while reducing stomach discomfort.

2. The role of permeability in drug release:

Permeability refers to the ability of water or solution to pass through the polymer coating. In enteric capsules, controlling permeability is crucial because it directly affects the release rate of the drug. By precisely adjusting the permeability of the coating, delayed or sustained release of the drug can be achieved.

3. Material selection to control permeability:

To control permeability, pharmaceutical scientists usually choose specific polymer materials. Commonly used materials include methyl methacrylate copolymers (such as Eudragit series) and hydroxypropyl methylcellulose. These materials have good stability in acidic environments and dissolve rapidly in alkaline environments.

By adjusting the ratio and properties of these polymers, the permeability of enteric-coated capsules can be controlled. For example, the permeability can be reduced and drug release can be delayed by increasing the cross-linking density of the polymer; conversely, reducing the cross-linking density can increase the permeability and accelerate drug release.

4. Multi-level design of permeability:

The coating of enteric-coated capsules can be designed into a multi-level structure, with different permeabilities in each layer to achieve more precise drug release control. The outer layer is usually a high-permeability material to ensure that the drug dissolves and releases rapidly after entering the small intestine. The inner layer can use a low-permeability material to control the continuous release of the drug throughout the small intestine.

This multi-level design can not only improve the bioavailability of the drug, but also reduce the degradation of the drug in the stomach, thereby improving the therapeutic effect.

5. Application of permeability regulation technology:

Permeability regulation technology has been successfully applied in many drug preparations. For example, some antibiotics and anti-inflammatory drugs can be precisely released in the small intestine through the permeability regulation technology of enteric-coated capsules, thereby improving the efficacy of the drug and reducing side effects.

6. Combination of sustained release and fixed-point release:

By controlling permeability, enteric-coated capsules can achieve a combination of sustained release and fixed-point release of drugs. This combination is particularly important in the treatment of some chronic diseases. For example, diabetic patients need long-term and stable drug release, and enteric-coated capsules can achieve this goal by regulating permeability.