title: Rheological evaluation of poloxamer as an in situ gel for ophthalmic use.
abstract: The contact time of a vehicle on the cornea is of utmost importance for ocular drug delivery. In the present study rheological measurements were performed to study the gel and the sol-gel transition of an in situ gel, Poloxamer 407. The rheological measurements and a small in vivo study of ocular residence times in humans were used to evaluate poloxamer as an ocular vehicle. An increasing concentration of poloxamer resulted in a slightly increasing elasticity of the gels and a decreasing sol-gel transition temperature. The contact time increased with increasing concentration of poloxamer which could be explained and correlated with the rheology of poloxamer solutions/gels mixed with simulated tear fluid. The maximum contact time for the preparations studied was about 1 h. The poloxamer system did not seem to be promising as an ophthalmic in situ gel due to the strong concentration dependence of the sol-gel transition temperature combined with the dilution that occurs in the eye.
authors.affiliation: Department of Pharmaceutics, Pharmacia Pharmaceuticals, Uppsala, S-751 82 Uppsala, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Edsman
authors.forename: J
authors.initials: J
authors.lastname: Carlfors
authors.forename: R
authors.initials: R
authors.lastname: Petersson
mesh_terms: D005782:Gels / Q000737:chemistry*; D009883:Ophthalmic Solutions / Q000737:chemistry*; D020442:Poloxamer / Q000737:chemistry*; D012212:Rheology
chemical_list: D005782:Gels; D009883:Ophthalmic Solutions; D020442:Poloxamer