Newer antiplatelet agents in acute coronary syndrome

Dual antiplatelet therapy comprising aspirin and a purinergic P2Y12 receptor inhibitor has long been the standard of care in patients with acute coronary syndrome (ACS). Clopidogrel is the most commonly used P2Y12 inhibitor,1 but its usefulness has been questioned, with 25-30% of patients achieving <25% inhibition of platelet activity. Moreover, onset (4-6 hours, even after a loading dose) and offset (5-7 days, the lifetime of platelets) of its activity are relatively slow. This slow offset is due to its irreversible binding to the P2Y12 receptor and may assume importance in patients with bleeding complications or in those requiring urgent surgical intervention. Slow onset is disadvantageous in patients with ACS, owing to the potential for propagation of thrombus in the interval until P2Y12 inhibition occurs.

The newer P2Y12 antagonists prasugrel and ticagrelor have more predictable pharmacokinetics and pharmacodynamics than clopidogrel; additionally, both are appreciably faster in their onset of action, and ticagrelor has a much faster offset than clopidogrel.2 Consequently, many cardiologists use these two agents over clopidogrel, which is reflected in some3 4—but not all5 6—guidelines for the management of ACS.

However, …