PREPARATION AND EVALUATION IN-VITRO OF SOLUTIONS AND O W MICROEMULSIONS CONTAINING LEVOBUNOLOL AS ION-PAIR/

Aqueous and aqueous-PEG 200 solutions, and o/w microemulsions containi ng levobunolol (LB) coupled to octanoic acid (OA) as lipophilic ion-pa ir were submitted to a preliminary investigation in vitro, in view of possible ophthalmic applications. Evaluation of the following was carr ied out: n-octanol/water partition coefficient, permeation through an artificial lipophilic membrane and through hairless mouse skin, isoton icity and eye irritation in albino rabbits. Permeation studies in aque ous and in aqueous-PEG 200 solutions through the artificial membrane i ndicated a higher apparent lipophilicity of LB-OA with respect to the drug alone. The transport rate of LB-OA through hairless mouse skin wa s lower from a microemulsion containing 0.5% w/w drug than from a wate r-PEG 200 solution simulating the continuous phase, thus suggesting a possible reservoir effect of the dispersed phase of the microemulsion. The microemulsion, which was isotonic and non-irritating on rabbit ey es, appears as a potentially interesting ophthalmic vehicle for LB.