3. Enteric Protection – modified / delayed release
Traditionally, enteric coatings with pH-sensitive polymers were used to delay the release of certain active ingredients. This is done either to protect the product from the acidic stomach environment or to protect the stomach from gastric irritation caused by the API.
GI Tract (pH Values/Retention time)
Basically it can be distinguished between a fast and a modified-release formulation.
In order to prevent that the dosage form disintegrates already in the mouth or esophagus, a water-soluble coating is sufficient, since the retention times could be low.
To perform drug release only upon entry into the small intestine, polymers must be used, which are dissolved only above the pH value of 5.5.
Enteric-coated drugs do not dissolve in the acidic condition of the stomach. While they readily dissolve in the alkaline pH of the small intestine.
Important: An enteric coating is only effective as long as the tablet is not crushed or cut/tilled before taking it.
- Stability in gastric fluid: pH 1.0 – 1.5 (fasted), pH 3.0 – 5.0 (fed)
- Quick dissolution & drug release in the duodenum: pH > 6.0
For example: Polymer with a defined number of functional acidic groups.