Rapid and Sensitive Method for Quantitative Determination of Lopinavir and Ritonavir in Human Plasma by Liquid Chromatography-Tandem Mass Specrtometry

A rapid and sensitive liquid chromatography-mass spectrometric (LC-MS-MS) method for the simultaneous determination of lopinavir and ritonavir in human plasma using abacavir as internal standard has been developed and validated. Sample preparation of plasma involved solid phase extraction. Detection was performed using an Applied Biosystems Sciex API 2000 Mass spectrometer. The assay of lopinavir and ritonavir was linear over the range of 50 ng mL(-1) to 20000 ng mL(-1) and 20 ng mL(-1) to 3000 ng mL(-1) respectively with a precision of < 15% and accuracy in the range of 85-115%. The limit of quantification in plasma for lopinavir and ritonavir was 50 ng mL(-1) and 20 ng mL(-1) respectively. The described method has the advantage of being rapid and easy and it could be applied in therapeutic monitoring of these drugs in human plasma.