Liquid chromatography-tandem mass spectrometric assay for the non-nucleoside reverse transcriptase inhibitor rilpivirine in human plasma.

An analytical method based on liquid chromatographic-tandem mass spectrometry (LC-MS/MS) was developed for the determination of the non-nucleoside reverse transcriptase inhibitor rilpivirine in human plasma using nevirapine as an internal standard. Analyte and the internal standard were extracted from human plasma by liquid-liquid extraction. The reconstituted samples were chromatographed on a C(18) column using a mixture of acetonitrile and 0.1% formic acid buffer (80:20, v/v) as the mobile phase at a flow rate of 0.5 mL/min. The linearity was confirmed in the concentration range 0.51-200 ng/mL in human plasma. Multiple reaction monitoring mode was used for quantification of ion transitions at m/z 367.2/195.1 and 267.1/226.1 for the drug and the internal standard, respectively. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. Extraction recoveries of drug from plasma were >69.5%. A run time of 2.50 min for each sample made it possible to analyze more than 300 plasma samples per day. The developed method is simple, rapid and sensitive for the determination of rilpivirine concentrations in real-time plasma samples obtained from pharmacokinetic studies.

Simultaneous determination of sitagliptin and simvastatin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study.

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and validated for simultaneous quantification of sitagliptin and simvastatin in human plasma. Carbamazepine was used as an internal standard (IS). The analytes and IS were extracted from the human plasma by liquid-liquid extraction technique. The reconstituted samples were chromatographed on an Alltima HP C(18) column using an isocratic solvent mixture [acetonitrile-5 mm ammonium acetate (pH 4.5), 85:15 (v/v)] at a flow rate of 1.0 mL/min. Method validation was performed as per Food and Drug Administration guidelines and the results met the acceptance criteria. The calibration curves obtained were linear (r(2) ≥ 0.99) over the concentration range of 0.10-501 and 0.05-105 ng/mL for sitagliptin and simvastatin, respectively. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. Both the analytes were found to be stable in a battery of stability studies. The method is precise and sensitive enough for its intended purpose. A run time of 3.0 min for each sample made it possible to analyze more than 300 plasma samples per day. The developed assay was successfully applied to a pharmacokinetic study in human volunteers.