Clopidogrel hydrogen sulfate is an antiplatelet agent which works by blocking platelets from sticking together and prevents them from forming harmful clots.

References:
[1]. Geiger, J., et al., Specific impairment of human platelet P2Y(AC) ADP receptor-mediated signaling by the antiplatelet drug clopidogrel. Arterioscler Thromb Vasc Biol, 1999. 19(8): p. 2007-11.
[2]. Roald, H.E., et al., Clopidogrel--a platelet inhibitor which inhibits thrombogenesis in non-anticoagulated human blood independently of the blood flow conditions. Thromb Haemost, 1994. 71(5): p. 655-62.
[3]. Ramadan, R., et al., Effects of Clopidogrel Therapy on Oxidative Stress, Inflammation, Vascular Function and Progenitor Cells in Stable Coronary Artery Disease. J Cardiovasc Pharmacol, 2013.