Aspirin and clopidogrel are two antiplatelet agents that have a potent protective effect against adverse vascular events[1]. They interfere with platelet activation in complementary but separate pathways.
Aspirin irreversibly inhibits cyclooxygenase, thus preventing the production of thromboxane A(2), which is a prothrombotic and vasoconstrictive substance. Clopidogrel is a specific and potent inhibitor of platelet aggregation, exerting its action via the P2Y12 receptor[4].
The combination of aspirin and clopidogrel has an even stronger antiplatelet effect, translating into superior antithrombotic protection in coronary, cerebral, or peripheral arterial disease, without an inordinate increase in adverse effects[1]. A number of clinical trials have demonstrated and confirmed the incremental benefit and efficacy of the combination of clopidogrel and aspirin therapy above and beyond that of aspirin alone[1].
However, the combination of clopidogrel and aspirin can significantly increase the bleeding time through a synergistic antiplatelet action[3]. Therefore, the risks and benefits of the combination should be carefully considered on an individual basis[4].
Citations:
[1] https://pubmed.ncbi.nlm.nih.gov/15974885/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4170318/
[3] https://www.sciencedirect.com/science/article/pii/S0741521402139450
[4] https://www.nps.org.au/radar/articles/clopidogrel-and-clopidogrel-with-aspirin-now-unrestricted-on-pbs
[5] https://www.ahajournals.org/doi/10.1161/01.str.0000181081.09262.e1
[6] https://www.ahajournals.org/doi/10.1161/01.cir.0000140675.85342.1b
