Prolonged effect of liposomes encapsulating pilocarpine HCl in normal and glaucomatous rabbits

The possibility of using liposomes as an ophthalmic drug delivery carrier for the lipophilic drug, pilocarpine HCl, was investigated on the eyes of normal and glaucomatous pigmented rabbits. The intraocular pressure (IOP) of rabbits was measured, using a Shi∅tz tonometer, as a function of time after topical administration with free drug, neutral and negatively charged multilamellar vesicles (MLVs) encapsulating pilocarpine HCl. The results showed that administration with neutral MLVs displayed the most prolonged effect with respect to negatively charged MLVs and free drug. The efficiency of MLVs encapsulating pilocarpine HCl, measured using spectrophotometric technique, was found to be 96% in our modified preparations. The storage stability of MLVs encapsulating pilocarpine HCl was investigated by measuring phase transition and size distribution using light scattering technique. The results show that liposomes encapsulating pilocarpine HCl have kept their integrity and physicochemical properties for at least 15 months, which makes them suitable for commercial use.