Delayed release, defined with lag phase and followed with release phase, is obtained when all surface of core is compression-coated. Pulsatile release defined by fast drug release after a certain lag time could be categorized within this group as well.

Lag time for drug release could be controlled by the application of different polymeric coats which were differentiated with triggering factors to control drug release as mainly mentioned in colonic drug delivery system.

Enteric/delayed release coatings consist of pH sensitive polymers, which means the coating remains intact in the acidic environment of the stomach and then solubilizes in the more alkaline environment of 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 alkaline (pH 7-9) environment present in the small intestine.

Enteric protection for solid oral dosage forms is required to:

1. prevent gastric mucosal irritation
2. protect a drug which is unstable in gastric fluids
3. delay release for local delivery in the intestine.

Materials used for enteric coatings
Materials used for enteric coatings include fatty acids, waxes, shellac, plastics, and plant fibers.

Read More : Enteric Coating Tablet : Polymer, Material and Formulation

Enteric Coated Tablet Application

Drugs that have an irritant effect on the stomach, such as aspirin, can be coated with a substance that will dissolve only in the small intestine. Likewise, certain groups of azoles (esomeprazole, omeprazole, [[pan 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 (fish burps).

Read More : Enteric Coating Tablet Process And Manufacturing