Polymers and Formulation Approaches for Floating In-Situ Gels

Developing gastroretentive drug delivery systems using floating in-situ gels is an innovative strategy. These formulations are given as liquids and, once in the stomach, solidify into a gel that can stay buoyant for a long time. Polymers are important aspects of these systems as they affect gel formation, viscosity, gel strength, floating behaviour, and release of drugs. Due to their excellent gel-forming properties and biocompatibility, natural polymers such sodium alginate, pectin, guar gum, xanthan gum, and gellan gum are often studied. Additionally, viscosity, gel strength, and drug release characteristics can be altered by adding synthetic and semi-synthetic polymers. On the basis of the mechanism of gel formation, floating in-situ gels can be developed using different approaches, including ion-activated, pH-triggered, temperature-sensitive, and gas-generating systems. While suitable polymer combinations can enhance the quality and stability of the produced gel, gas-forming agents are especially helpful for adding buoyancy. The selection of polymer type, concentration, polymer combination, and gas-generating agent plays an important role in achieving suitable floating lag time, floating duration, and drug release. This work discusses the major polymers used in floating in-situ gels and the different formulation approaches employed to obtain effective gastroretentive systems.