A validated liquid chromatography and tandem mass spectrometric method for simultaneous quantitation of tenofovir, emtricitabine, and efavirenz in human plasma and its pharmacokinetic application

A novel, rapid, and sensitive liquid chromatography-tandem mass spectrometric method was developed and validated for the simultaneous quantification of tenofovir, emtricitabine, and efavirenz in human plasma. Nevirapine was used as an internal standard. The analytes and the internal standard were extracted from human plasma sample by solid-phase extraction technique (SPE). The reconstituted samples were chromatographed on a Chromolith ROD C18 column (50 x 4.6 mm; 5 [mu]) by gradient elution using a mixture of ammonium acetate buffer (5 mM) and 0.1% formic acid in acetonitrile as the mobile phase at a flow rate of 1.0 mL min super(-1). The calibration curve obtained was linear (r super(2)> or = 0.9990) over the concentration range of 2.5-650 ng mL super(-1) for tenofovir and 10-4000 ng mL super(-1) for emtricitabine and efavirenz. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies, and the authenticity in the measurement of clinical data is demonstrated through incurred samples reanalysis (ISR).