Abstract: AIM: To establish LC-MS method in determination of oxymatrine in plasma of Beagle dogs and to investigate its absolute bioavailability.METHODS: According to a randomized two-period crossover design, the Beagle dogs were iv 6 mg·kg^-1 and ig 30 mg·kg^-1 of oxymatrine, respectively.Drug concentration in plasma was assayed by HPLC ESI MS. RESULTS: The linearity of oxymatrine ranged from 2 to 5 000 μg·L^-1(r=0.9990).The detection limits of oxymatrine was 0.6μg·L^-1 .The values of RSD of within day and between day were less than 4.2 %.The recovery of this method was more than 96.7 %.The disposition was conformed to a two-compartment model .The C_max, T_max, T_1/2β, AUC_0→∝ and absolute bioavailability of oxymatrine were 2.42±0.97μg·L^-1,1.0±0.3h,5.54±1.58h,6.12±1.08μg·L^-1·h^-1 and (19.4±9.0)%, respectively.CONCLUSION: This study provides a simple, reliable and special method for determining concentrations of oxymatrine in plasma of Beagle dog.Oxymatrine shows low absolute bioavailability in Beagle dogs.

Key words: oxymatrine, liquid chromatography mass determination, pharmacokinetics, Beagle dogs, absolute bioavailability