Pharmacokinetics of Venlafaxine

Aim To establish a method to determine the concentration of venlafaxine in human plasma using High performance Liquid Chromatography-Fluoresence (HPLC-F). Methods The analytical column was Diamonsil C18(150mm×4.6mm,5 μm);the mobile phase was acetonitrile-phosphate buffer solution(pH 3.0)-triethylamine(33.5∶ 66.5∶ 1,V/V/V);the flow rate was 1.0ml/min;and the injection volume was 20 μl,and the internal standard was maprotiline. Plasma samples were extracted with n-hexane and isopropyl alcohol with fluorimetric detection (λex 276 nm, λem 596 nm). Results The linear range of venlafaxine in human plasma was 10～800ng · ml-1(r=0.999 9). The lowest detectable plasma concentration was 16.99ng · ml-1(S/N3). The extraction and relative recoveries of venlafaxine over plasma concentration 30,150,600ng · ml-1 were 81.51%～91.08% and 98.7 %～112.6 % respectively. The RSD of within-day and between-day were less than12% and 10%(n=5), respectively. The parameters:t1/2(6.57±2.81)h,Tmax(3.11±0.93)h,Cmax(273.38±75.44)ng · ml-1, AUC(0～t)(2 237.54±816.67)ng · h · ml-1,AUC(0～∞)(2 456.13±838.30)ng · h · ml-1.Conclusion The method is proved to be convenient,specific,sensitive enough to be applied to pharmacokinetic studies of venlafaxine in human plasma.