Tuesday, 7 January 2014

What is Enteric Coated Tablets - (Why enteric coated tablets are not recommended for spliting,crushing or chewing ?)


 
Enteric Coated Tablets
=
Gastro resistant Tablets
( Why enteric coated tablets are not recommended for spliting,crushing or chewing ?)
 
 

 Enteric coated tablets are solid dosage forms which are designed to bypass the stomach and release the drug in small intestine ( i.e enteric coated tablets are colon targeted drug delivery systems).

The word “enteric” indicates small intestine; therefore enteric coatings prevent release of medication before it reaches the small intestine. Most enteric coatings work by presenting a coated surface that is stable at the highly acidic pH (ex. in stomach - where pH is 1.0-3.5), but breaks down rapidly at a less acidic pH (ex. Colon - where pH is 7.9 - 8.0).

An enteric coating is a barrier that controls the location of oral medication in the digestive system where it is absorbed. The enteric coated polymers remain unionise at low pH, and therefore remain insoluble. But as the pH increases in the GIT, the acidic functional groups are capable of ionisation, and the polymer swells or becomes soluble in the intestinal fluid. Materials used for enteric coatings include CAP, CAT, PVAP and HPMCP, fatty acids, waxes, shellac etc.

Usually entering coating is done for following reasons: 

·       To protect acid labile active pharmaceutical ingredients (e.g Omeprazole), from the acidic environment of the stomach.

·       To prevent gastric distress or nausea from a drug due to irritation (e.g. Sodium salicylate,Aspirin etc).

·       For the delivery of drugs that are optimally absorbed in the small intestine to their primary absorption site in their most concentrated form.

·       To provide a delayed-release component for repeat action.

·       Required for minimizing first pass metabolism of drugs.

 

The choice of the polymer and the thickness of the coated layer are critical to control the pH solubility profile of the enteric coated dosage form. The most common drugs which cause stomach ulcers like aspirin, diclofenac and naproxen are frequently available with enteric coatings. Omeprazole, which is a drug which stops the stomach from producing acid, is itself broken down in acid and therefore the drug generally has an enteric coating around it either as a granule in the capsules or as a granule in the dispersible form.  

Enteric coatings  are also used in the formulation of sustained action preparations as the release of medicament is delayed by the time taken for the tablet to pass from the mouth to the intestine. Cellulose acetate phthalate and eudragit are  the most widely used polymers  for enteric coating.

If enteric coated tablets are chewed or crushed, the tablet core will be exposed to acidic environment of stomach, this will increase the chance of a stomach ulcer (If API is irritant to stomach), or affect the bioavailability of drug in the body (if it is degraded by the acid in the stomach). For this reason a patient should never crush or chew enteric coated tablets.

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