Major heart attacks are caused by a number of factors, the two major of which are furring up of a coronary artery with atheroma and then sudden clot formation on this area leading to a blockage and interruption of blood flow. The clots that lead to heart attacks are largely made of clotting blood cells (platelets) that in health repair blood vessels and inhibit spontaneous bleeding. One of the main treatment strategies for heart attacks is to make these cells less "sticky". Aspirin is a main stay of anti-platelet treatment in the United Kingdom (UK) and in addition one of three other oral antiplatelet agents acting on the same platelet activation pathway (P2Y12 receptor) is licensed for use. When a patient is admitted with a major heart attack, they are treated with emergency primary percutaneous coronary intervention (PPCI) a technique where a wire and balloon are used to reopen the coronary artery and then usually a stent (a slotted metal tube) is placed to keep the artery open. Aspirin and one of the P2Y12 inhibitor agents are given to prevent further clots and all have been shown to reduce negative events following heart attacks and angioplasty with stent insertion. There are increasing data, including from our own institution, showing that in the setting of heart attacks, the oral P2Y12 inhibitors are poorly absorbed and have little effect at the time of most need, i.e. soon after dosing while the primary PCI is being performed.