Enteric coating

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An enteric coating is a barrier applied to oral medication that controls the location in the digestive system where it is absorbed. Enteric refers to the small intestine, therefore enteric coatings prevent release of medication before it reaches the small intestine.

Most enteric coatings work by presenting a surface that is stable at the highly acidic pH found in the stomach, but breaks down rapidly at a less acidic (relatively more basic) pH. For example, they will not dissolve in the acidic juices of the stomach (pH ~3), but they will in the higher pH (above pH 5.5) environment present in the small intestine. Materials used for enteric coatings include fatty acids, waxes, shellac and plastics.

Drugs that have an irritant effect on the stomach, such as aspirin, can be coated with a substance that will only dissolve in the small intestine. Similarly, certain groups of azoles (esomeprazole, omeprazole, pantoprazole and all grouped azoles) are acid-unstable. For such types of drugs, enteric coating added to the formulation tends to avoid the stomach's acidic exposure, delivering them instead to a basic pH environment (intestine's pH 5.5 and above) where they do not degrade, and give their desired action.

Recently, some companies have begun to utilize enteric coatings on fish oil (omega 3 fatty acids) supplements. The coating prevents the fish oil capsules from being digested in the stomach, which has been known to cause a fishy reflux.

Sometimes the abbreviation "EC" is added beside the name of the drug to indicate that it is enteric coated.

Composition of coatings

• Cellulose acetate phthalate (CAP)
• methyl acrylate-methacrylic acid copolymers
• cellulose acetate succinate
• hydroxy propyl methyl cellulose phthalate
• hydroxy propyl methyl cellulose acetate succinate (hypromellose acetate succinate)
• polyvinyl acetate phthalate (PVAP)
• methyl methacrylate-methacrylic acid copolymers
• Sodium alginate and stearic acid

See also

• Phthalates

External links

Definition of "enteric coating" in the free dictionary website