In ACS, when should a P2Y12 inhibitor be loaded?

• A. At diagnosis for STEMI, before PCI for NSTEMI/UA
• B. After PCI
• C. Only after discharge
• D. Never

Answer: (A)

Loading a P2Y12 inhibitor early in ACS is about ensuring rapid, reliable platelet inhibition during the highest-risk period around coronary intervention. In STEMI, you want antiplatelet effects in place as soon as possible, so give the loading dose right after diagnosis (in the emergency department or even pre-hospital) and before the patient goes to the cath lab. This speeds up the onset of antiplatelet activity for the upcoming PCI and helps prevent thrombotic complications during the procedure and in the immediate post-procedure period.

For NSTEMI or unstable angina when an invasive strategy is planned, the same principle applies: administer the loading dose before PCI to achieve adequate platelet inhibition during the intervention and early post-PCI period. Delaying the loading dose until after PCI leaves a window of higher risk for thrombus formation, including stent thrombosis if a stent is placed.

In contrast, waiting until after discharge misses the critical time when rapid platelet inhibition is most beneficial, and never delaying is unsafe.

Note that newer agents (ticagrelor, prasugrel) provide faster, more consistent onset than clopidogrel, reinforcing the rationale to load early when an invasive strategy is anticipated.