Antiplatelet therapy in coronary artery disease

Dr Matthew Sibbald is an associate professor in the Division of Cardiology at McMaster University and interventional cardiologist at Hamilton Health Sciences.

What should be taken into consideration when choosing or switching antiplatelet agents in patients with coronary artery disease (CAD)?

Matthew Sibbald, MD, MHPE, PhD: It is not often that we have to switch antiplatelet agents. Currently most practitioners use a combination of clopidogrel, ticagrelor, or prasugrel. Ticagrelor and prasugrel have more potent platelet inhibition through the P2Y₁₂ receptor.

When we think about switching, usually there is a reason. Either we are trying to intensify therapy because the patient has had a recurrent event or a stent thrombosis on aspirin and clopidogrel alone, or we are trying to deintensify therapy because the patient has had a bleeding event. Sometimes we are trying to de-escalate therapy or switch because patients have had a side effect related to one of the antiplatelet medications. I think the rationale and the way of switching depends on whether you are intensifying or de-escalating therapy.

When you are intensifying therapy, I think it makes sense to load with the new agent. Despite the patient already being on clopidogrel, and maybe even being loaded with clopidogrel, when they present with a new myocardial infarction (MI), the PLATO (Platelet Inhibition and Patient Outcomes) trial would have given them an additional load of 180 mg of ticagrelor on top of that. That showed a reduction in events as early as 6 hours after the load. It is similar with prasugrel. I think the evidence would suggest that a load in the setting of intensification of therapy makes sense.

If you are trying to de-escalate therapy because the patient had a bleed, then probably it does not make sense to load the patient. I would introduce it at a regular maintenance dose. And usually that means going back to clopidogrel rather than to ticagrelor or prasugrel.

Finally, when we are switching for side effects, I think the jury is out in how you do that, but either option makes sense.