MUCOADHESIVE OPHTHALMIC VEHICLES - EVALUATION OF POLYMERIC LOW-VISCOSITY FORMULATIONS

A series of polyanionic natural or semi-synthetic polymers (polygalact uronic acid, hyaluronic acid, carboxymethylamylose, carboxymethylchiti n, chondroitin sulfate, heparan sulfate and mesoglycan) were evaluated as potential mucoadhesive carriers for ophthalmic drugs. Solutions co ntaining cyclopentolate (CY) or pilocarpine (PI) as salts (or polyanio nic complexes) with the acidic polymers, all showing a low viscosity, were tested for miotic (resp. mydriatic) activity in albino rabbits. I n the case of some polymeric complexes, small but significant increase s of the areas under the activity vs. time curves (AUC) over reference cyclopentolate hydrochloride (CYHCl) or pilocarpine nitrate (PINO3) v ehicles, and significant AUC decreases after removal bf precorneal muc in by treatment with N-acetylcysteine were observed. A correlation was found between these data, considered indicative of the occurrence of a mucoadhesive interaction ''in vivo'', and ''in vitro'' viscometric d ata expressing the polymers-mucin force of interaction. The advantages and limitations of the mucoadhesive non-viscous approach in the formu lation of ophthalmic vehicles are presented and discussed.