Most of the oral dosage forms possess several physiological limitations such as variable gastrointestinal transit because of variable gastric emptying leading to non-uniform absorption profiles, incomplete drug release and shorter residence time of the dosage form in the stomach. This leads to incomplete absorption of drugs having absorption window especially in the upper part of the small intestine, as once the drug passes down the absorption site, the remaining quantity goes unabsorbed.Since many drugs are well absorbed in the upper part of the gastrointestinal tract, such high variability may lead to non-uniform absorption and makes the bioavailability unpredictable. Hence, a beneficial delivery system to control and prolong the gastric emptying time and can deliver drugs in higher concentrations to the absorption site to show local action in the stomach requires a specialized delivery system. So the purpose of this study was to lengthen the stay of drug in its favorable absorption area and prolonging the release of the drug by formulating it into an effervescent gastro-retentive drug delivery system. Это и многое другое вы найдете в книге Gastroretentive Drug Delivery System for oral Anti Diabetic Agents (Shailendra Singh,Amlan Mishra and Raghvendra Sharma)