Aspirin has an established role in the treatment of ACS and secondary prevention of ischaemic heart disease. In the landmark trial of aspirin in ACS, ISIS-2 (1988), it conferred a benefit of similar magnitude to thrombolysis. The addition of a second antiplatelet agent (a P2Y12 inhibitor) to aspirin is known to improve outcomes in both NSTE-ACS (Yusuf, Zhao et al. 2001) and STEMI (Chen, Jiang et al. 2005, Sabatine, Cannon et al. 2005). There are 2 major classes of oral P2Y12 inhibitor: irreversibly binding thienopyridine agents, such as clopidogrel or prasugrel, and reversibly-binding drugs, such as the cyclo-pentyl triazolopyrimidine ticagrelor.