[Ocular pharmacokinetics of pilocarpine micron emulsion in rabbits]

To compare the pharmacokinetics of pilocarpine micron emulsion with generic pilocarpine solution in the aqueous humor.

60 albino rabbits were used and were divided into 20 groups, each consisting of 3 animals. 10 groups received 2% generic pilocarpine 50 microl as controls; 10 groups received 50 microl of 2% pilocarpine micron emulsion in the conjunctival sac. The aqueous humor was withdrawn at 5, 10, 30, 40, 60, 90, 120, 180, 240 and 360 min. after instillation. The drug was extracted from aqueous humor with dichloromethane. The drug was analyzed by reversed phase high pressure liquid chromatography (HPLC).

Pilocarpine micron emulsion therapy gave higher aqueous humor concentration of the drug than drops at all time periods tested except 5 min. time point (P = 0.0003 - 0.042). The area under curve of micron emulsion was 3 times as much as that of drops. There was a two-fold increase in ocular bioavailability of pilocarpine due to the therapy with micron emulsion. Measurable amounts of drug following 2% micron emulsion were still observed at 360 min. while drug levels at 180 min. following 2% drop therapy were nil.

Our study results demonstrated significantly increase in ocular bioavailability of pilocarpine due to the therapy with micron emulsion. Our finding indicates that a novel topical preparation of pilocarpine incorporated in micron emulsion might serve as a long acting antiglaucoma agent, and less frequent applications are necessary with it than with conventional drops.