Cardiovascular/Antiplatelet

Antiplatelets

also: aspirin · clopidogrel · ticagrelor

Overview

Secondary prevention of arterial thrombosis (ACS, stroke/TIA, PAD, post-stent). Cross-references Haematology.

Mechanism

Aspirin irreversibly acetylates COX-1 → ↓thromboxane A₂ for the platelet lifespan (~7–10 days). Clopidogrel/ticagrelor block the platelet P2Y₁₂ ADP receptor (clopidogrel irreversible prodrug; ticagrelor reversible). Both impair platelet aggregation.

Indications

ACS (dual antiplatelet therapy)
Secondary prevention post-MI / ischaemic stroke / TIA
PAD
Coronary stent (DAPT)

The agents

AspirinCOX-1 inhibitor

irreversible, 75 mg OD

Lifelong post-ACS/stroke.

ClopidogrelP2Y₁₂ (prodrug)

CYP2C19 activated

1st-line single agent after ischaemic stroke/TIA (NICE).

TicagrelorP2Y₁₂ (reversible)

ACS DAPT; causes dyspnoea.

PrasugrelP2Y₁₂ (prodrug)

PCI; avoid if prior stroke/TIA.

Adverse effects

GI bleeding / peptic ulcerserious

Aspirin; consider PPI cover.

Bruising / bleedingcommon

Dyspnoeaclassic

Ticagrelor (adenosine-mediated).

Aspirin hypersensitivity / bronchospasmcommon

Cautions & contraindications

Active major bleedingall

Aspirin in children <16paediatric

Reye syndrome.

Prasugrel after stroke/TIAall

Excess intracranial bleeding.

Interactions

Clopidogrel + omeprazole/esomeprazole → reduced activation (use lansoprazole)
Combination with anticoagulants ↑bleeding
NSAIDs ↑GI bleed

Monitoring & kinetics

Bleeding (clinical); Hb if suspected

Oral. Stop ~7 days pre-surgery for irreversible agents where bleeding risk high.

Source: BNF — Antiplatelet drugs