An enteric coating is a polymer coating applied to oral medications to protect acid-sensitive drugs from dissolving in the stomach. Enteric coatings are insoluble in low pH environments but dissolve in the higher pH of the small intestine. This allows drugs to pass through the stomach intact and be released and absorbed in the intestines. Common polymers used for enteric coatings include cellulose acetate phthalate, acrylic polymers like Eudragit, and hydroxypropyl methylcellulose phthalate. Enteric coatings help improve drug stability, absorption, and prevent gastric irritation.

2.  An enteric coating is a barrier that controls
the location of oral medication in the
digestive system where it is absorbed.
 The word “enteric” indicates the small
intestine.
 These are polymer coatings which are
insoluble at low pH, but soluble at high pH.
 Enteric coatings are prepared from gastric
resistant polymers.
 Drug release rate is controlled by its exposed
pH.

4.  To protect acid labile drugs.
 For optimal absorption.
 To prevent gastric stress due to drug
irritation.
 To show local action on intestine.
 To provide delayed release.

5.  Resistance to gastric fluid.
 Susceptible/permeable to intestinal fluid.
 Formation of continuous film.
 Compatibility.
 Stability.
 Non toxic or no pharmacologic activity.
 Ease of printing.

6. 1. Cellulose acetate phthalate (CAP)
CAP is widely used but it has major disadvantage
that it dissolves above pH 6, thus delaying the drug
release as the ideal material may dissolve around pH
5.
It is having hygroscopic nature and relatively
permeable to gastric fluids.
It form brittle film so it required hydrophobic
plasticizers.

7. 2. Acrylate polymers
Two types of commercial available acrylic
resins are
i) Eudragit L ii)Eudragit S
Soluble at pH 6 and 7 respectively.
Eudragit L is available as an organic solution
(Isopropanol), solid or aqueous dispersion.
Eudragit S is available only as organic
solution and solid.

8. 3. Hydroxypropyl Methylcellulose
Phthalate (HPMCP)
Three grades are available
i)HPMCP 55 (HP 50) ii) HPMCP 50 (HP 55)
iii)HPMCP 55S (HP 55S)
These polymers dissolved at a lower pH (around 5
to 5.5) than CAP and acrylic copolymers.
They show higher bioavailability of some drugs.
HP 55 used for general enteric preparations.
These are quit stable then CAP because of absence
of acetyl group.

9. 4. Polyvinyl Acetate Phthalate (PVAP)
Prepare by esterification of partially
hydrolyzed polyvinyl acetate with phthalic
anhydride.
It is similar to HP-55 in terms of stability
and pH-dependent solubility.
Supplied as ready-to-use.

10. Examples of enteric coated
formulation
Brand Generic Manufacturer
Omez Omeprazole Dr. Reddy’s
Cardizem CD 360mg Diltiazem Aventis

11. ADVANCEMENT IN TABLET
COATING MATERIAL
 Aqueous based coating materials like
colloidal dispersion (30%) of polymer
Ethyl Cellulose (aqua coat and aquateric)
are now replacing organic solvent based
coating materials.
 Water based controlled tablet coatings by
Latex and Pseudo latex of acrylate
polymers and ethyl cellulose have been
reported.

12.  Cross-linked product of hydroxyl-end
blocked polydimethyl- siloxane has been
developed as water based controlled
release tablet coating system.

13. References …..
 Aulton, Michael E., Taylor, Kevin M. G., Aultons
pharmaceutics : the design and manufacturing of
medicines, 4th edition (International), churchill livingstone,
Elsevier publication, page no. 562.
 Khar, Roop K, Vyas, S. P., Ahmad, Farhan J, Jain, Gaurav
K, The Theory and Practice of Industrial Pharmacy, 4th
edition, CBS publishers and distributers, page no. 502
 Sharma, Kapil, Sharma, Priyanka, A review on formulation
and evaluation aspects of enteric coated pellets on
http://www.pharmatutor.org/articles/review-on-
formulation-evaluation-aspects-of-entric-coated-pellets .
 Dhilman, Vandna, Modgil, Swati, Nagpal Meenu, Jain,
Uprendra K, Coating technology and its recent advances –
a review on http://www.pharmatutor.org/articles/coating-
technology-its-recent-advances-review%20?page=0,1 .