Objective To determine the concentration and dynamic changes of
tetramethylpyrazine hydrochloride in aqueous humor following
intraperitoneal injection in rabbits. Methods Forty-four New Zealand white rabbits were randomly divided into 11 groups.The aqueous humor were collected at 0,0.25,0.50,0.75,1,1.5,2,3,5,8 and 12 hours following intraperitoneal injection of 80 mg/kg of
tetramethylpyrazine hydrochloride,and the concentration of tetramethylpyrazine was detected by reversed phase high performance liquid chromatography(RP-HPLC). Results The concentration-time data of tetramethylpyrazine hydrochloride in aqueous humor was subjected to two-compartment open model.The
pharmacokinetics parameters were found to be as following: C max= 13.73 μg/mL,t max= 0.28 h,t 1/2α= 0.42 h,t 1/2β= 3.97 h and CL= 1.34 L/h.The observed concentration of tetramethylpyrazine hydrochloride in aqueous humor was 11.91± 1.41 μg/mL at 15 min,and the maximum concentration reached 18.71± 1.13 μg/mL at 30 min.The concentration of tetramethylpyrazine hydrochloride in aqueous humor was decreased gradually thereafter to a much lower concentration of 0.06 μg/mL at 5 hours and almost undetectable in 8-12 hours. Conclusion The method of RP-HPLC is specific,accurate and sensitive to the measurement of tetramethylpyrazine hydrochloride in aqueous humor.Tetramethylpyrazine can penetrate blood-aqueous barriers and enter aqueous humor.