Class Explorer · Cardiovascular
Antiplatelet agents
Drugs that stop platelets aggregating, each at a different point: thromboxane synthesis, ADP signalling, or the final common receptor. They prevent arterial (white, platelet-rich) clot, which is why they are not interchangeable with anticoagulants.
Members
Also in this class: Ticagrelor · Prasugrel · Dipyridamole. Full pages arrive as the library grows.
Compare the members
- Target
- COX-1, irreversible
- Onset
- Minutes (chewed)
- Practical note
- Chew, do not swallow, in suspected ACS
- Target
- P2Y12, irreversible
- Onset
- Hours; faster with a loading dose
- Practical note
- Prodrug; CYP2C19-dependent
Shared across the class
- Indications
- Secondary prevention after myocardial infarction or ischemic stroke · Coronary stents · Peripheral arterial disease
- Adverse effects
- Bleeding, gastrointestinal above all · Bruising
- Contraindications
- Active major bleeding
- Monitoring
- Bleeding, overt and occult · Hemoglobin if there is any suspicion of GI loss · Adherence: a missed clopidogrel dose after a recent stent is a stent-thrombosis risk, not an inconvenience
What makes each agent different
- Aspirin blocks COX-1 irreversibly for the platelet's whole 7 to 10 day life; clopidogrel blocks P2Y12 irreversibly for the same span. Both need new platelets to recover, which is why 'stopping five days before surgery' is a platelet-turnover calculation, not a half-life one.
- Clopidogrel is a prodrug requiring CYP2C19; poor metabolisers get less effect, and this is the mechanism behind the omeprazole interaction.
- Ticagrelor and prasugrel are more potent and more bleeding-prone; they are cardiology's choices, not a routine substitution.
Antiplatelet plus anticoagulant is not additive risk, it is multiplicative. Every day of dual or triple therapy should have a stated end date.
Aspirin for primary prevention has quietly retreated from most guidelines; its net benefit in a person who has never had an event is close to zero and can be negative.
Last reviewed 2026-08-16 · Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed.