OBJECTIVE To develop an HPLC method for the quantification of huperzine A in rat plasma an d in injection site after im microspheres.METHODS Samples were extracted by liquid-liquid extraction and separated on a Kromasil -C 18( 4.6 mm× 250 mm, 5 μm).The mobile phase of drug content d etermination in plasma and muscle homogenate was acetonitrile- 0.2% triethyl amine)20∶100 and 25∶75 respectively.The detection wavelength was 310 nm.RESULTS The assay range of the two methids was 2.5~ 500 μg·L -1...