Making Enteric Coated Tablets

Find innovative production technology for making enteric coated tablets and connect directly with world-leading specialists

When taking a tablet, it is usually the job of our stomach to break down the medication to make it ready to be absorbed into the bloodstream. However, some drugs are not meant to be dissolved in the stomach because the acidic pH of the stomach can disintegrate the drug, making it no longer effective. Using tablet coating equipment that applies a polymer barrier to the tablet makes it possible to protect it from stomach acidity.

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Enteric coated tablets forming

Enteric coated tablets labeling

Enteric coated tablets formulation

Enteric coated tablets drying

Enteric coated tablets compaction

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Why is an enteric-coated tablet needed?

So if it can’t be the stomach’s job to dissolve the tablets, whose job will that be? Enteric comes from the Greek word énteron, meaning intestine. As we mentioned earlier, some drugs like Rabeprazole or Pantoprazole are destroyed by the acidic pH of the stomach acids.

The funny thing is that these drugs are meant to reduce the acids in the stomach, but they are destroyed by the acids themselves without having a chance to provide their effectiveness. So they need to bypass the stomach and be released in the small intestine.

The enteric coating ensures that the tablet remains unaltered and stable in the stomach’s acidic pH (pH ~3) but breaks down and dissolves at higher pH (alkaline, pH 7–9) of the intestine. On the other hand, some drugs like aspirin and NSAIDs (Nonsteroidal anti-inflammatory drugs) can also cause side effects such as gastric irritation or nausea. The enteric coating protects the gastric mucosa from the drug itself. Another reason for enterically coated tablets is to provide a delayed release of the medication.

Polymers used for enteric coating

The enteric coating is nothing more than applying a polymer film on a tablet. Obviously, the polymers used for this coating must be resistant to gastric fluids. Polymers for enteric coating remain unionized at low pH, but when they reach the small intestine, they become soluble and swell, and begin to dissolve at a pH of 5.0-5.5. In addition to this, they should be compatible with the drug substrate and the coating solution and should be non-toxic in nature.

Examples of enteric film-coating polymers are cellulose acetate phthalate (CAP), which is the oldest and the most used for enteric coating, Cellulose acetate trimellitate (CAT), Hydroxypropyl methylcellulose phthalate (HPMCP) and Shellac.

Applying a polymer film using tablet coating equipment

When preparing an enteric coating formulation, you need to pay attention to the mixing part. The mixture should be uniform and fine enough to pass through the coating system. The most common tablet coating equipment used for enteric coating is a pan coating system. This involves spraying the film-forming material onto the tablet surface as the tablets rotate in the pan.

Hot air is applied which helps the organic solvent evaporate and form the coat over the tablets. You need to repeat the process according to the desired thickness of the tablet’s film.

Enteric-coated tablets are pills that have a special coating designed to protect the active ingredients from stomach acid. While protecting, these tablets are still able to release the important API in the intestine. This feature is particularly important for drugs like naproxen and ibuprofen. Which have been known to cause irritation of the stomach lining. And thus, can cause ulcers. Enteric coated tablets are commonly used in the treatment of arthritis and inflammation and can be found at most local pharmacies.