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Abstract

The validated analytical method was applied for estimation of vorapaxar in aqueous and human plasma with vorapaxar-D5 as an internal standard by using UPLC-ESI-MS/MS. The chromatographic separation was achieved with 5mM Ammonium Formate Buffer (pH: 4.0): Methanol: Acetontrile, (40:30:30, % v/v) using the Pursuit XRs-100Å, C18, 4.6 × 50 mm, 10 µm. The total analysis time was 3.5 min and flow rate was set to 0.2 ml/min. The mass transitions of vorapaxar and vorapaxar-D5 obtained were m/z 591.4447.2 and 498.6447.2. The standard curve shows correlation coefficient (r 2) greater than 0.999 with a range of 0.01-200.0 ng/ml using the linear regression model. The developed method was applied successfully for studying the pharmacokinetics of vorapaxar in rabbits. INTRODUCTION: Vorapaxar is a reversible antagonist of the protease-activated receptor-1 (PAR-1) expressed on platelets, but its long halflife makes it effectively irreversible. Vorapaxar inhibits thrombin-induced and thrombin receptor agonist peptide (TRAP)-induced platelet aggregation in-vitro studies. Vorapaxar does not inhibit platelet aggregation induced by adenosine diphosphate (ADP), collagen or a thromboxane mimetic and does not affect coagulation parameters ex-vivo. PAR-1 receptors are also expressed in a wide variety of cell types, including endothelial cells, neurons, and smooth muscle cells, but the pharmacodynamic effects of vorapaxar in these cell types have not been assessed 1-2 .