In Situ Gelling Systems for Drug Delivery

Implication for health policy/practice/research/medical education: Development of polymeric in situ gels for controlled release of various drugs provides a number of advantages over conventional dosage forms. Some important advantages of these smart systems are ease of application and reduced frequency of administration, as well as protection of the drug from environmental conditions. Published by DOCS. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In situ gelling systems are polymeric formulations that are in sol forms before entering in the body, but change to gel forms under the physiological conditions. The sol-gel transition depends on one or a combination of different stimuli, like pH change, temperature modulation, solvent exchange, ultra violet irradiation and the presence of specific ions or molecules. Drug delivery systems having such properties can be widely used for sustained delivery vehicle preparation of the bioactive molecules. Some important advantages of these smart systems are ease of application and reduced frequency of administration, as well as protection of drug from environmental condition changes. Various natural and synthetic polymers undergo in situ gel forming and potentially can be used for oral, buccal, rectal, vaginal, ocular, intraperitoneal and parenteral drug delivery. Pectin, xyloglucan, gellan gum, chitosan and alginic acid are some of the natural polymers (1). The pectin gelation occurs in the presence of calcium ions. When pectin is administered orally, divalent cations induce gel formation in the stomach (2). Xyloglu-can exhibits thermally reversible gelation with body temperature and have been used for oral, ocular, rectal and peritoneal drug delivery. An oral liquid in situ gelling system could successfully produce sustained release formulation and solve quick transit of liquid preparations from the gastrointestinal tract (1). Dilute aqueous solutions of alginates form firm gels, on addition of di and trivalent metal ions. The formation of covalent bonds, leading to the perception of the insoluble cross linked alginate hy-drogels, reduces the release of embodied drugs in algi-nate matrices. A formulation containing sodium alginate and calcium ions, being added to sodium citrate delays gelation process until the administered solution reaches the acidic environment of the stomach. Additionally, buc-cal adhesive in situ gels have been formulated, using ion or pH sensitive polymers, to prolong the contact time of antifungal drugs in the oral cavity (1). Ophthalmic in situ gels have been …