Determination of the concentration of Venlafaxine in human plasma by HPLC

OBJECTIVE To establish a method for determining the concentration of venlafaxine in human plasma by HPLC.METHODS The drug from plasma was analyzed in a reverse phase HPLC system C18 column(150 mm×4.6mm,5μm);mobile phase consisted of 0.03 mol·L-1 ammonioum-methanol(19:81);the flow rate was 1.0mL·min-1;the detection wavelength was at 254 nm.Ethyl acetate and dichloromethane(80∶20) was used as extracting solvent.RESULTS The average recoveries of venlafaxine in low,middle and high concentrations(20.0,160.0,640.0ng·mL-1) were 101.32%,98.63%and 99.61%,respectively.The intra-day and inter-day variation(RSD) was less than 10%(n=5).The calibration curve of venlafaxine showed good linearity,r=0.9989(n=8),over the range of 10.0~800.0ng·mL-1.The regression equation was Y=22.75X+2.07,r=0.9989(n=8).The minimum detectable concentration of venlafaxine was 5.0ng·mL-1.CONCLUSION The method is sensitive,accurate,simple and quick,it can be used for clinical drug monitoring and pharmacokinetics studies of venlafaxine.