RHEOLOGICAL EVALUATION OF POLOXAMER AS AN IN-SITU GEL FOR OPHTHALMIC USE

The contact time of a vehicle on the cornea is of utmost importance fo r ocular drug delivery. In the present study rheological measurements were performed to study the gel and the sol-gel transition of an in si tu gel, Poloxamer 407. The rheological measurements and a small in viv o study of ocular residence times in humans were used to evaluate polo xamer as an ocular vehicle. An increasing concentration of poloxamer r esulted in a slightly increasing elasticity of the gels and a decreasi ng sol-gel transition temperature. The contact time increased with inc reasing concentration of poloxamer which could be explained and correl ated with the rheology of poloxamer solutions/gels mixed with simulate d tear fluid. The maximum contact time for the preparations studied wa s about 1 h. The poloxamer system did not seem to be promising as an o phthalmic in situ gel due to the strong concentration dependence of th e sol-gel transition temperature combined with the dilution that occur s in the eye. (C) 1998 Elsevier Science B.V.