Purpose  To assess the ocular absorption of raceanisodamine, an analytical HPLC method was developed for the determination of raceanisodamine in rabbit aqueous humor and to study its pharmacokinetics in
rabbit aqueous humor.
Methods  Proteinaceous material in rabbit aqueous humor is extracted by ethylacetate. An aliquot of the supernatant is analyzed by HPLC.The chromatography was performed on a reversed-phase encapped column (Dikma,250*4.6 mm, i.d. 5 μm C₁₈ ) at 30°C with a mobile phase consisting of acetonitrile in 10mM monopotassium phosphate solution with 0.47 ml·L perchloric acid acetate (pH 3.0, 11.5: 88.5, v/v). The flow rate was 1.0 ml·min^-1.Raceanisodamine was monitored with UV detector at 214 nm.
Results  Good linearity between concentration of raceanisodamine (c, ng·mL^-1) in aqueous humor and peak area was obtained for y=0.226x+0.008, R²=0.996(n=3)in the range from 0.1-0.15 ng·mL^-1.The lower limit of quantification (LOD) of the method was 20.0 ng·mL^-1,indicating that the method is adequate for sensitive pharmacokinetic studies.The average recoveries were determined as 122.8%, 97.06% and 106.7% at aconcentration of 0.2, 1, 3 ng·mL^-1. With in-day and inter-daycoefficients of variation were lower than 5%. 24 healthy rabbits were given the eye drops to study the pharmacokinetic bioavailability of the raceanisodamine eye drops. The concentration-time course followed a 1-compartment open model and the major parameters were listed: t_max: (10.00±3.01) h, C_max:
(12401.9±18.34) ng·mL^-1, t _1/2 (44.77±2.19) h, AUC _0-8: (29065.16±44.78) ng·mL^-1, MRT: (30.7±0.63) h.
Conclusion  This method is selective, sensitive and reproducible for the determination of raceanisodamine in rabbit aqueous humor and is suitable for the pharmacokinetic study of raceanisodamine in ophthalmic system.