Objective: To establish LC-MS method in the determination of oxymatrine and its
metabolite in plasma and investigate their
pharmacokinetics in beagle dogs. Method: Lichrospher C18 column (4.6 mm×250 mm, 5 μm )was used as the analytical columnm maintained at 25 ℃. The mobile phase was consisted of 10 mmol·L~(-1) CH_3COONH_4 and CH_3OH (25∶75). Flow rate was 1mL·min~(-1). Electrospray ionization(ESI)was carried out. The ESI ion source was set in positive ion polasity mode.The selective ion monitoring (SIM) was set at m/z 265.1 and 249.2. Result: The linearity ranged from 2 to 5 000 ng·mL~(-1)(r=0.999 1). The detectction of
oxymatrine and its metabolite were 0.6 and 0.3 ng·mL~(-1).The RSD(%) within day and between day was less than 4.7 %. The recovery of this method was more than 96.5%. The disposition was conformed to a two-compartment model. The T_(1/2), T_(max), C_(max), MRT, AUC_(0→24 h) of oxymatrine were ((5.5±)1.58) h,(1.0±0.30) h,(2 418.3±970.78) ng·mL~(-1),(3.2±0.64) h,(5 797.4±908.16) ng·mL~(-1)·h accordingly. The corresponding T_(1/2), T_(max), C_(max), MRT, AUC_(0→24h) of matrine were(9.8±2.77) h,(1.9±1.09) h,(1 532.4±494.86) ng·mL~(-1),(4.4±1.97) h,((5 530.5±)1 042.65) ng·mL~(-1)·h. Conclusion: This assay was highly senstive, rapid, simple and specific enough for determining concentrations of oxymatrine and its metabolite matrine in plasma of beagle dog.