Validation of simultaneous quantitative method of HIV protease inhibitors atazanavir, darunavir and ritonavir in human plasma by UPLC-MS/MS.

OBJECTIVES: HIV protease inhibitors are used in the treatment of patients suffering from AIDS and they act at the final stage of viral replication by interfering with the HIV protease enzyme. The paper describes a selective, sensitive, and robust method for simultaneous determination of three protease inhibitors atazanavir, darunavir and ritonavir in human plasma by ultra performance liquid chromatography-tandem mass spectrometry. MATERIALS AND METHODS: The sample pretreatment consisted of solid phase extraction of analytes and their deuterated analogs as internal standards from 50 µL human plasma. Chromatographic separation of analytes was performed on Waters Acquity UPLC C18 (50 × 2.1 mm, 1.7 µm) column under gradient conditions using 10 mM ammonium formate, pH 4.0, and acetonitrile as the mobile phase. RESULTS: The method was established over a concentration range of 5.0-6000 ng/mL for atazanavir, 5.0-5000 ng/mL for darunavir and 1.0-500 ng/mL for ritonavir. Accuracy, precision, matrix effect, recovery, and stability of the analytes were evaluated as per US FDA guidelines. CONCLUSIONS: The efficiency of sample preparation, short analysis time, and high selectivity permit simultaneous estimation of these inhibitors. The validated method can be useful in determining plasma concentration of these protease inhibitors for therapeutic drug monitoring and in high throughput clinical studies.

Development and validation of a sensitive and rapid method to determine naratriptan in human plasma by LC-ESI-MS-MS: application to a bioequivalence study.

A simple, sensitive, selective, and rapid high-performance liquid chromatography-tandem mass spectrometry method is developed and validated for the quantitation of naratriptan, using sumatriptan as internal standard (IS). The method included liquid-liquid extraction of naratriptan and IS with methyl-tert-butyl ether and dichloromethane mixture from 100 µL human plasma. The chromatographic separation is achieved on ACE C18 (50 mm × 2.1 mm, 5 µm) analytical column under isocratic conditions, using 0.1% acetic acid and acetonitrile (15:85, v/v) at a flow-rate of 0.4 mL/min. The precursor → product ion transitions for naratriptan (m/z 336.10 → 98.06) and IS (m/z 296.09 → 251.06) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and positive ion mode. The linearity of the method for naratriptan is determined in the range of 103-20690 pg/mL with the analysis time of 1.5 min. The method is fully validated according to USFDA guidelines. A systematic post-column infusion study is conducted for ion-suppression due to endogenous matrix components. The process efficiency of analyte (96%) and IS (93%) from spiked plasma samples was consistent and reproducible. The application of the method is demonstrated by a bioequivalence study of 2.5 mg naratriptan tablet formulation in 31 healthy volunteers under fasting conditions.

Rapid and specific liquid chromatographic tandem mass spectrometric determination of tenofovir in human plasma and its fragmentation study.

A simple, specific, and high throughput liquid chromatography tandem mass spectrometry method is developed for the determination of tenofovir, a nucleotide reverse transcriptase inhibitor, in human plasma using adefovir as internal standard. Plasma samples are prepared by solid-phase extraction of the analyte and internal standard using Waters Oasis MCX cartridges (1 cc, 30 mg). The chromatographic separation is achieved on a reversed-phase Chromolith, C18 analytical column (100 mmx4.6 mm, 5 microm) under isocratic conditions. The mobile phase consists of 0.5% formic acid in water and acetonitrile (90:10, v/v) to give a run time of 1.8 min. The protonated precursor-->product ion transitions for tenofovir and IS are monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ion mode. The fragmentation pathways for tenofovir are studied by varying the collision energy (5-55 V) using nitrogen as CAD gas. A linear dynamic range of 3.1-1002.0 ng/mL is established using 0.2 mL plasma sample. The method is fully validated for its sensitivity, selectivity, accuracy and precision, matrix effect, recovery, stability, and dilution integrity. It is applied to a bioequivalence study in 43 human subjects after oral administration of 300 mg tablet formulation under fasting conditions.