Abstract: AIM: To develoPa reversed RP-HPLC method for the study of pharmacokinetics and bioavailability of oxymatrine in male volunteers.METHODS: 1.0 ml plasma sample was applied to C18 cartridges activated with methanol.After washing, the cartridge was eluted with 2 ml mixed liquor of methanol and chloroform.The elution was evaporated to dryness with nitrogen gas at 60 ℃.The residue was dissolved with 80 μl mobile phase solution, and 20 μl was injected onto a Diamonsil ODS C₁₈column (5 μm, 4.6 mm ×150 mm).The mobile phase was 0.005 mol·L^-1sodium heptanesulfonate (pH=3.5, adjusted with H3PO4) -acetonitrile (80∶20).The flow rate was 1.0 ml·min^-1.An ultraviolet detector was set at 220 nm wavelength to monitor eluted components.A single oral dose of 600 mg of oxymatrine dispersible tablet and oxymatrine capsule was given to each of 18 healthy volunteers in an open randomized two-way crossover design.RESULTS: The linear range was 0.025 -1.600 mg·L^-1, r =0.9999.The limit of determination was 0.025 mg·L^-1.The method recovery was 96.5 %-110.2 %.Within-day precision (RSD) and between-day precision (RSD) were less than 10 %.The main pharmacokinetic parameters obtained showed no statistically significant difference between two preparations.CONCLUSION: The method is sensitive, specific and reproducible for the determination of oxymatrine concentration in human plasma.Two products are bioequivalent.

Key words: oxymatrine, pharmacokinetics, RPHPLC, solid phase extraction