A review on in situ gel forming ophthalmic drug delivery systems

Nowadays ophthalmic route of administration of drugs is rapidly progressing and more studies are going on in formulating ophthalmic drug delivery systems. There are many conventional dosage forms available in the market like ointments, eye drops etc. The main drawback with these types of formulations is rapid drainage of the instilled dose due to the lacrimal fluid secretions and blinking of the eye lids. In order to minimize this drainage and to increase the ocular residence time and corneal contact time, in situ gel forming formulations are developed. In these systems sol to gel transformation takes place due to the environmental changes like pH, temperature, ionic strength. Some polymers like sodium alginate, HPMC are frequently used to initiate these processes. These formulations can be assessed for viscosity, clarity, gel strength, gelling capacity, gelling time, texture, isotonicity, sterility, ocular irritancy, anti-microbial efficacy, in vitro drug release, ex vivo release, in vivo absorption, in vivo retention and stability.