Development and validation of a HPLC-MS/MS method for the determination of venlafaxine enantiomers and application to a pharmacokinetic study in healthy Chinese volunteers.

An HPLC-MS/MS method has been developed and validated for the determination of venlafaxine enantiomers in human plasma and applied to a pharmacokinetic study in healthy Chinese volunteers. The method was carried out on a vancomycin chiral column (5 µm, 250 × 4.6 mm) maintained at 25°C. The mobile phase was methanol-water containing 30 mmol/L ammonium acetate, pH 3.3 adjusted with aqueous ammonia (8:92, v/v) at the flow rate 1.0 mL/min. A tandem mass spectrometer with an electrospray interface was operated in the multiple reaction monitoring mode to detect the selected ions pair at m/z 278.0 → 120.8 for venlafaxine enantiomers and m/z 294.8 → 266.7 for estazolanm (internal standard). The method was linear in the concentration range of 0.28-423.0 ng/mL. The lower limit of quantification was 0.28 ng/mL. The intra-and inter-day relative standard deviations were less than 9.7%. The method was successfully applied for the evaluation of pharmacokinetic profiles of venlafaxine enantiomers in 18 healthy volunteers. Validation parameters such as the specificity, linearity, precision, accuracy and stability were evaluated, giving results within the acceptable range. Pharmacokinetic parameters of the venlafaxine enantiomers were measured in the 18 healthy Chinese volunteers who received a single regimen with venlafaxine hydrochloride capsules. The results show that AUC((0-∞)) , C(max) and t(1/2) between S-venlafaxine and R-venlafaxine are significantly different (p < 0.05).