Antiplatelet treatment
Exam Tips
- In UK exams, state clearly: antiplatelets are mainly for secondary prevention; routine primary prevention is generally not advised.
- Quote core ACS dosing: aspirin 300 mg loading then 75 mg daily; DAPT usually up to 12 months unless bleeding risk alters duration.
- For PAD, clopidogrel 75 mg daily is preferred over aspirin in many patients.
- Always mention bleeding risk stratification, GI protection, and drug-interaction checks (especially with anticoagulants/NSAIDs).
- Differentiate antiplatelet versus anticoagulant indications: arterial platelet-rich thrombosis versus venous/cardioembolic fibrin-rich thrombosis.
Definition
Antiplatelet treatment is the use of drugs that reduce platelet activation and aggregation to lower arterial thrombus formation, especially in atherosclerotic disease where platelet-rich clots predominate. In UK practice, it is used mainly for secondary prevention after events such as acute coronary syndrome, ischaemic stroke/TIA, and symptomatic peripheral arterial disease, while routine primary prevention is generally not recommended because bleeding risk often outweighs benefit.
Pathophysiology
Endothelial injury (for example from smoking, diabetes, and elevated LDL cholesterol) promotes atherosclerotic plaque formation; plaque disruption exposes thrombogenic material, triggering platelet adhesion, activation, and aggregation with downstream arterial occlusion or distal embolization. Antiplatelet drugs interrupt different points in this pathway: aspirin irreversibly inhibits COX-1 and thromboxane A2 synthesis; clopidogrel/prasugrel (thienopyridines) and ticagrelor inhibit P2Y12-mediated ADP signalling; dipyridamole and cilostazol increase platelet cAMP via phosphodiesterase inhibition. This mechanism explains benefit in arterial disease (MI, stroke, PAD) and the principal harm of bleeding. See Figure from a haemostasis chapter in core medicine/cardiology texts showing platelet activation (COX-1 and P2Y12 pathways).
Risk Factors
- Atherosclerotic risk factors: cigarette smoking, diabetes mellitus, elevated LDL cholesterol, hypertension, chronic kidney disease
- Previous MI, ischaemic stroke/TIA, symptomatic PAD, or prior coronary stent/CABG
- High bleeding risk: previous GI bleed/peptic ulcer disease, older age/frailty, low body weight, thrombocytopenia
- Concomitant drugs increasing bleeding risk (anticoagulants, NSAIDs, SSRIs, corticosteroids)
- Alcohol excess and uncontrolled hypertension (increase haemorrhagic complications)
Clinical Features
Symptoms
- Usually no symptoms from the drug itself; treatment is started because of atherothrombotic presentations (chest pain, focal neurological deficit, exertional calf pain)
- Adverse-effect symptoms: dyspepsia, epigastric pain, melaena, haematemesis
- Mucosal bleeding symptoms: epistaxis, gum bleeding, easy bruising, haematuria
- Red-flag haemorrhage symptoms: sudden severe headache, neurological deficit, collapse
Signs
- Bruising/purpura and prolonged bleeding from minor trauma
- Pallor, tachycardia, postural hypotension if significant blood loss
- PR bleeding/melaena on examination suggesting GI haemorrhage
- Condition-specific signs prompting therapy (for example ACS ECG changes, stroke focal signs, reduced peripheral pulses in PAD)
Investigations
Management
Lifestyle Modifications
- Aggressive cardiovascular risk reduction: smoking cessation, Mediterranean-style diet, exercise, weight management, BP/diabetes/lipid control
- Bleeding-safety counselling: report melaena, haematemesis, haematuria, prolonged epistaxis, or neurological symptoms urgently
- Medication safety: avoid over-the-counter NSAIDs unless advised; limit alcohol; carry an up-to-date antithrombotic medication list
- Peri-procedural planning with dentistry/surgery teams rather than self-stopping antiplatelets
Pharmacological Treatment
Single antiplatelet therapy (secondary prevention first-line)
- Aspirin 75 mg once daily (usual long-term dose)
- Clopidogrel 75 mg once daily if aspirin is contraindicated or not tolerated
For suspected ACS or suspected TIA within 1 week, initial aspirin 300 mg loading may be used in appropriate clinical pathways. Routine primary prevention with antiplatelets is generally not recommended.
Dual antiplatelet therapy after ACS/PCI
- Aspirin 75 mg once daily plus ticagrelor 90 mg twice daily (up to 12 months; 60 mg twice daily if extended)
- Aspirin 75 mg once daily plus prasugrel 10 mg once daily (or 5 mg once daily if <60 kg or age >=75 years)
- Aspirin 75 mg once daily plus clopidogrel 75 mg once daily
Typical duration up to 12 months, shortened in high bleeding risk or extended in selected high ischaemic-risk patients with good tolerance. Contraindications/safety: active bleeding, previous intracranial haemorrhage, hypersensitivity; review interactions and bleeding risk before combining agents.
PAD-focused regimens
- Clopidogrel 75 mg once daily preferred
- Aspirin 75 mg once daily if clopidogrel unsuitable
- Rivaroxaban 2.5 mg twice daily plus aspirin 75 mg once daily in selected high-ischaemic-risk/low-bleeding-risk patients (specialist decision)
Balance limb/cardiovascular benefit against bleeding risk; combination pathway requires careful renal function and bleeding-risk review.
Other specialist antiplatelets
- Dipyridamole modified-release 200 mg twice daily (stroke/TIA secondary prevention in selected patients, alone or with aspirin)
- Cilostazol 100 mg twice daily for intermittent claudication (specialist initiation; stop if no benefit after 3 months)
Avoid cilostazol in heart failure due to safety concerns. IV agents (for example cangrelor, glycoprotein IIb/IIIa inhibitors) are specialist in-hospital therapies around PCI/ACS.
GI protection when bleeding risk is high
- Proton pump inhibitor co-prescription (for example lansoprazole 15-30 mg once daily or omeprazole 20 mg once daily, depending on interaction profile)
Use gastroprotection in higher-risk patients (previous ulcer/GI bleed, dual therapy, concomitant anticoagulant/NSAID, older age). Check local interaction guidance when combining PPIs with clopidogrel.
Surgical / Interventional
- Percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) pathways require coordinated antiplatelet timing
- Perioperative antiplatelet interruption/continuation should be individualized by thrombotic versus bleeding risk and procedure type
- Urgent management of major haemorrhage may require temporary cessation of antiplatelet drugs and specialist haemostasis support
Complications
- Major or clinically relevant non-major bleeding
- Gastrointestinal bleeding and peptic ulcer complications
- Intracranial haemorrhage (rare but serious)
- Haematuria, epistaxis, gum bleeding, easy bruising
- Adherence problems due to dyspepsia or nuisance bleeding
- Recurrent thrombotic events if therapy is omitted early after ACS/PCI
Prognosis
When matched to indication and bleeding risk, antiplatelet therapy substantially reduces recurrent arterial events and improves long-term cardiovascular outcomes, particularly after ACS, stroke/TIA, and in PAD. Prognosis worsens with poor adherence, premature discontinuation (especially post-stent), or major haemorrhage; regular review of net clinical benefit is therefore essential.
Sources & References
✅NICE Guidelines(1)
- Antiplatelet treatment[overview]
📖Textbook References(11)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1416)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 28)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 682)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 27, 28)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 682)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1416)[context]
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 491)[context]
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 491)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 813)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 812, 813)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 38)[context]