Enteric coating refers to a specialized protective layer applied to oral medications, such as tablets or capsules. This barrier is designed to prevent the medication from dissolving or breaking down too early in the digestive tract. It ensures the active ingredients remain intact as they pass through the stomach’s acidic environment. This coating functions as a polymer barrier that protects the drug until it reaches a suitable location for release and absorption.
The Purpose of Enteric Coating
The application of an enteric coating serves two main purposes. One primary reason is to protect the active ingredients within the medication from degradation by highly acidic stomach fluids. Some drugs are unstable or can be inactivated by the stomach’s pH, which ranges from 1.5 to 2.0. Without this protective layer, these medications would lose their effectiveness before they could be absorbed.
Another significant purpose of enteric coatings is to protect the stomach lining from potentially irritating substances found in certain medications. Many drugs, like some pain relievers, can cause stomach upset, irritation, or even ulcers if they dissolve directly in the stomach. By keeping the medication from releasing its contents in the stomach, the coating helps minimize these gastrointestinal side effects. This ensures the medication reaches the small intestine, where it can be absorbed with less risk of harming the stomach.
How Enteric Coatings Function
The mechanism by which enteric coatings work relies on their pH-sensitive properties. The coating is designed to remain stable and insoluble in the acidic environment of the stomach. Stomach acid has a pH around 1 to 3. This low pH keeps the polymer barrier intact, preventing the medication from dissolving prematurely.
As the medication moves from the stomach into the small intestine, the environment becomes less acidic and more alkaline. The pH in the small intestine ranges from 6 to 9. This shift in pH causes the enteric coating to swell and then dissolve. Once the coating dissolves, the active ingredients of the medication are released into the small intestine, where they can be absorbed into the bloodstream. Common materials used for these coatings include polymers like cellulose acetate phthalate (CAP) and methacrylic acid copolymers, which resist acid but dissolve in alkaline conditions.
Common Uses of Enteric Coatings
Enteric coatings are used for various medications and supplements where targeted delivery or stomach protection is beneficial. A common example is aspirin. Aspirin can irritate the stomach lining, and an enteric coating helps prevent this by ensuring the drug bypasses the stomach and dissolves in the small intestine. This reduces the risk of gastrointestinal issues like ulcers or bleeding.
Certain enzyme supplements also use enteric coatings. These enzymes are designed to aid digestion, but stomach acid would degrade them before they could reach the intestines where they are needed. The coating protects these sensitive enzymes, allowing them to remain active until they reach the small intestine. Similarly, some probiotics and fish oil supplements are enteric-coated to ensure the beneficial bacteria or omega-3 fatty acids survive the stomach and are released in the intestines. Additionally, some proton pump inhibitors (PPIs) are enteric-coated because they would be degraded by stomach acid if not protected.