Development and Application of Liquid Chromatographic Method for Simultaneous Determination of Elvitegravir, Tenofovir Disoproxil Fumarate, Emtricitabine, and Cobicistat in Fixed Dosage Form

Quad pill is fi xed-dose combinations containing four drugs in a single tablet with the intention of reducing the number of tablets that need to be taken. Elvitegravir (ELVT)/cobicistat (COB)/emtricitabine (EMCB)/tenofovir disoproxil fumarate (TDF) is a complete regimen intended for treatment of HIV infection. Developing a single analytical method for the estimation of individual drugs in a QUAD is very challenging, due to the formation of drug-drug and drug-excipient interactions. The present study demonstrates the applicability of chromatographic method to develop a new, sensitive, single high-performance liquid chromatography method for the simultaneous quantitative determination of four antiviral agents in fi xed pharmaceutical dosage form. Chromatographic separation of the four antiviral drugs was achieved by using a gradient elution at a fl ow rate of 1.0 ml/min on Inertsil ODS 3V C 18 column (250 m × 4.6 mm, 5 μm particle size, 100 A pore size) at ambient temperature. Mobile phase A of the gradient solvent system was KH 2 PO 4 (0.02 M) in 1000 ml of water and by adjusting the pH to 2.5 with dilute orthophosphoric acid and mobile phase B was acetonitrile. Ultraviolet detection at 240 nm was employed to monitor the analytes. A linear response was observed for EMCB over the concentration range 20-240 μg/ml, for TDF over the concentration range of 30-360 μg/ml, for ELVT and COB over the concentration range of 15-180 μg/ml. Limit of detection for EMCB, TDF, ELVT, and COB were 0.02 μg/ml, 0.03 μg/ml, 0.75 μg/ml, and 3 μg/ml, respectively. Limit of quantifi cation for EMCB, TDF, ELVT, and COB were 0.06 μg/ml, 0.09 μg/ml, 2.25 μg/ml, and 9 μg/ml respectively. Key words: Cobicistat, elvitegravir, emtricitabine, gradient-high performance liquid chromatography, quadpill, tenofovir disoproxil fumarate.