In oral drug delivery, the extent of drug absorption can be limited by the gastrointestinal transit time of the dosage form and the residence time of the drug at the site of absorption. For some drugs localisation in the upper gastrointestinal tract could significantly improve the drug absorption. As the gastrointestinal tract is coated with a mucus gel layer, increased contact of the dosage form with the mucus layer may lead to increased gastric residence times.
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