Canonical Question

Phaemacopeia – Antiplatelet Agents

Master answer

Anti-platelet drugs

COX Inhibitors	Aspirin	MoA	Cyclooxygenase-1 (COX-1) produces precursor to thromboxane A2 (TxA2)           Aspirin irreversibly binds and inactivates
		A/E	GI bleeding and ulceration Kidney injury Reye’s syndrome Bronchospasm In overdose – metabolic acidosis
		Elimination	CYP2C19, metabolites in urine
		Duration	Irreversible COX-1 inhibition → last until platelet turnover (7-10 days)
P2Y12 receptor antagonists	Clopidogrel Ticagrelor	MoA	P2Y12 is an ADP receptor, which causes platelet recruitment and activation (by inducing activation of GPIIb/IIIa)
		A/E	Bleeding, itch
		Elimination	dogrel is a prodrug, requiring activation by CYP450 Prasugrel is inactivated by CYP450
		Duration	Irreversible receptor inactivation → 7-10 days
Glycoprotein IIb/IIIa inhibitors	Abciximab Tirofiban	MoA	glycoprotein IIb/IIIa binds von Willebrand factor on damaged vascular wall, and fibrinogen to create a pro-clot with other platelets
		AE	Higher rate of bleeding than aspirin and ADP receptor antagonists
		Elimination	Variable
		Duration	6-12 hours after cessation of infusion
Phosphodiesterase inhibitors	Dipyridamole	MoA	Inhibits phosphodiesterase → increased platelet cAMP Also causes coronary vasodilation → useful in angiograms
		AE	Bleeding, hypotension
		Elimination	Mainly glucuronides in bile 5% in urine
		Duration	3 hours

Click to Open CICMWrecks Table: Anti-platelet Agents