Objective: To develop an RP-HPLC method for assay of pilocarpine in rabbit ocular aqueous humor.
Methods: The RP-HPLC method was performed on a column of ODS-C(18) with the mobile phase consisting of 0.5% of triethylamine (TEA) of phosphate solutions (10 mmol/L, pH 2.5) and acetonitrile (98/2,v/v). The detection wavelength was 215 nm and flow rate was 1.0 ml/min. Ninety albino rabbits were divided into 3 groups (30 in each):group 1 received 50 microl of eye drops containing 1% generic pilocarpine, group 21% mixture pilocarpine solution consisting of aqueous sample and liposome and group 31% liposome pilocarpine, respectively. The aqueous humor was withdrawn at 5, 10, 30, 40, 60, 90, 120, 180, 240 and 360 min. Pilocarpine was extracted from aqueous humor with dichloromethane.
Result: The linear calibration curve was obtained in the concentration range of 0.1 - 20 microg/ml. The average recovery was (68.1+/-2.7)% (n=9). Inter-day and intra-day RSD were 4.33% and 2.87%, respectively. In three formations 1% liposome pilocarpine was the best for the areas under curve and measurable amounts.
Conclusion: The RP-HPLC method is simple and reliable for pilocarpine measurement in ocular aqueous. Liposome formulation can significantly increase the bioavailability of pilocarpine in ocular aqueous.