A novel LC-MS/MS method for simultaneous quantification of tenofovir and lamivudine in human plasma and its application to a pharmacokinetic study.

A new, rapid, sensitive and specific LC-MS/MS method has been developed and validated for the simultaneous quantification of tenofovir and lamivudine in human plasma using abacavir as an internal standard. An API-4000 LC-MS/MS with electrospray ionization was operated in multiple-reaction monitoring mode for the analysis. The analytes were extracted from plasma by solid-phase extraction technique using an Oasis HLB cartridge. The reconstituted samples were chromatographed on a Chromolith ROD speed C(18) column using a mixture of 0.1% formic acid in water and acetonitrile (90:10 v/v) at a flow-rate of 1 mL/min. The method was validated as per the FDA guidelines. The calibration curves were found to be linear in the range of 5-600 ng/mL for tenofovir and 25- 4000 ng/mL for lamivudine. The intra- and inter-day precision and accuracy results were well within the acceptable limits. A run time of 2.8 min consumed for each sample made it possible to analyze more samples per day. The proposed assay method was found to be applicable to a pharmacokinetic study in human male volunteers.