RHEOLOGICAL EVALUATION OF GELRITE(R) IN-SITU GELS FOR OPHTHALMIC USE

One of the reasons for the relatively low bioavailability of conventio nal eye drops is their short precorneal contact times. In situ gels ar e promising ocular drug delivery systems since they are conveniently d ropped into the eye as a liquid whereafter they undergo a transition i nto a gel. Due to their elastic properties hydrogels resist ocular dra inage leading to longer contact times. In this paper the rheology of G elrite(R) in situ gels was studied. A complementary in vivo study for determining precorneal contact times in humans and in rabbits was perf ormed. The elastic moduli of the gels increased with increasing concen tration of electrolytes. At physiological concentration of the electro lytes, the elasticity of the gels was independent of Gelrite(R) concen tration. The human contact times increased up to 20 h with decreasing osmolality of the formulations. The results indicate that a high rate of the sol/gel transition results in long contact times. (C) 1998 Else vier Science B.V.