Pilocarpine bioavailability from a mucoadhesive liposomal ophthalmic drug delivery system

Abstract The influence of a mucoadhesive polymer (Carbopol 1342) on the in-vitro release and in-vivo ocular bioavailability of pilocarpine nitrate entrapped in liposomes has been investigated. Coating of reverse phase evaporation vesicles (REVs) by Carbopol 1342 was achieved by incubating pre-formed vesicles in a 0.05% pH 5.0 polymer solution for 5 min. The in-vitro release phase of pilocarpine was extended by the presence of the polymer coating. The adsorbed film was therefore shown to provide a substantial barrier to drug release. Bioavailability was evaluated in albino rabbits by measuring the intensity and duration of the miotic response. Carbopol 1342 coated REVs showed a larger area under the miotic intensity curve (AUC) and a longer duration of action compared to uncoated REVs. No significant difference of area under the miotic intensity curve and duration of action was found between coated REVs and phosphate-buffered saline (PBS) solution containing the same concentration (0.5% w/v) of pilocarpine nitrate.