Anti-platelet medications
The classes of anti-platelet drugs include:
- Irreversible cyclooxygenase (COX) inhibitors
- Aspirin
- Adenosine diphosphate (ADP) receptor inhibitors
- Clopidogrel (Plavix)
- Prasugrel (Effient)
- Ticagrelor (Brilinta)
- Ticlopidine (Ticlid)
- Glycoprotein IIB/IIIA inhibitors (intravenous use only)
- Abciximab (ReoPro)
- Eptifibatide (Integrilin)
- Tirofiban (Aggrastat)
- Adenosine reuptake inhibitors
- Dipyridamole (Persantin / Asasantin)
- Thromboxane inhibitors and phosphodiesterase inhibitors
Asprin is recommended for all patients with ACS, in the absence of hypersensitivity. It should be given along with one of the following anti-platelet agents as indicated.
Clopidogrel, Prasugrel and Ticagrelor are all oral anti-platelet agents. They are in the thienopyridine class of ADP receptor inhibitors that affect the P2Y12 receptor on the platelet cell membrane. They inhibit ADP binding to its platelet receptor, and the subsequent ADP mediated activation of the GPIIb/IIIa complex, thereby inhibiting platelet aggregation.
Clopidogrel and Ticagrelor are indicated for the prevention of atherothrombotic events in adult patients with acute coronary syndrome (ACS), including patients managed medically, and those who are managed with percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).
Prasugrel is indicated for patients with ACS who are going to undergo percutaneous coronary intervention (PCI).
Administration Guidelines
Note: With regards to choice of antiplatelet agents use, local policies may vary. This information has been obtained from current national guidelines, derived from expert consensus - check your local institutional policies (and/or consult your cardiology service), before prescribing these medications.
Aspirin
- 300mg loading dose followed by 100-150mg daily.
Clopidogrel (trade name Plavix)
300-600mg loading dose followed by 75mg daily.
Prasugrel (trade name Effient)
60mg loading dose followed by 10mg daily.
The TRITON study compared Prasugrel to Clopidogrel and found it to inhibit platelet aggregation more rapidly and more consistently with significantly reduced rates of ischaemic events but with increased major bleeding.
It is used as an alternative to Clopidogrel at the time of PCI. However, it should not be used in patients over 75 years old, patients with low body weight (<60kg) or history of TIA or stroke.
Ticagrelor (trade name Brilinta)
180mg loading dose followed by 90mg bd.
The PLATO trial compared Ticagrelor to Clopidogrel and found it had a significant reduced rate of death from vascular causes, MI, or stroke without an increase in overall major bleeding but with an increase in the rate of non-procedure-related bleeding. It has a more rapid onset and more pronounced platelet inhibition than Clopidogrel.
Ticagrelor is currently preferred over Clopidogrel for use in patients with STEMI or NSTEACS at intermediate to high risk of an ischaemic event. It should not be used in patients with AV conduction disorders (2nd and 3rd degree AV block) and asthma or COPD.
Glycoprotein IIb/IIIa inibitors
Inhibitors prevent the binding of fibrinogen and von Willebrand factor to GP IIb/IIIa receptors on the platelet. They work by preventing platelet aggregation and thrombus formation. They are indicated at the time of PCI in selected high risk patients.
Australian guidelines recommend balancing the risk of poor outcome from ACS against the estimated bleeding risk to determine when these agents should be used - for further information see the following guidelines.
Further References and Resources
Chew DP, Scott IA, Cullen L, et al. NHFA/CSANZ: Australian clinical guidelines for the management of Acute Coronary Syndromes 2016. Med J Aust 2016; 205 (3): 128-133.
Amsterdam EA, Wenger NK, et al. 2014 AHA/ACC Guideline for the Management of Patients with Non-ST-Elevation Acute Coronary Syndromes. Circulation 2014; 64(24).