An enteric coating is a polymer barrier applied to oral medication that prevents its dissolution or disintegration in the gastric environment.[1] This helps by either protecting drugs from the acidity of the stomach, the stomach from the detrimental effects of the drug, or to release the drug after the stomach (usually in the upper tract of the intestine).[2] Some drugs are unstable at the pH of gastric acid and need to be protected from degradation. Enteric coating is also an effective method to obtain drug targeting (such as gastro-resistant drugs).
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Most enteric coatings work by presenting a surface that is stable at the intensely acidic pH found in the stomach, but breaks down rapidly at a higher pH (alkaline pH). For example, they will not dissolve in the gastric acids of the stomach (pH ~3), but they will in the alkaline (pH 7–9) environment present in the small intestine.[4][5] The time required for an enteric-coated dosage form to reach the intestine mostly depends on the presence and type of food in the stomach. It varies from 30 minutes up to 7 hours, with an average time of 6 hours.[6] Although some studies indicated that larger sized dosage forms may require additional time for gastric emptying, others suggested that the size, shape, or volume of the tablet possess no significant effects instead.[7][8][9] Enteric coated granules emptying rate is, however, less affected by the presence of food and present the more uniform release and reproducible transit time typical of the multiparticulates dispersion.
