Floating dosage systems in drug delivery

The identification of new diseases and the resistance shown toward existing drugs calls for the introduction of new therapeutic molecules. In response, a large number of chemical entities have been introduced, of which some have absorption over the entire gastrointestinal tract (GIT), some have absorption windows (i.e., absorption sites, especially the upper part of the small intestine), and some have poor solubility in intestinal media altogether. The drugs belonging to the second and third categories, and the drugs required for local action in the stomach, require a specialized delivery system. All the above requirements can be met and effective delivery of the drugs to the absorption window, for local action and for treatment of gastric disorders such as gastro-esophageal reflux, can be achieved by floating dosage systems (FDS). To date, a number of FDS involving various technologies, carrying their own advantages and limitations, were developed, such as single- and multiple-unit hydrodynamically balanced systems (HBS), single- and multiple-unit gas-generating systems, hollow microspheres, and raft-forming systems. Various factors such as gastrointestinal physiology, dosage form characteristics, and patient-related factors control the behavior of FDS. This review discusses the anatomy and physiology of the stomach, the gastric emptying process, factors affecting the gastric retention of dosage forms, and various techniques adopted in the development of FDS.