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Antiplatelet — COX Inhibitor Pregnancy: D (third trimester, full dose)

Aspirin (Antiplatelet)

Brand names: Aspirin 75 mg, Anadin

Adult dose

Dose: 75 mg once daily (secondary prevention); 300 mg loading dose (acute arterial event)
Route: oral
Frequency: once daily
Max: 300 mg loading; 75 mg daily maintenance
Enteric-coated for GI protection (though evidence limited); take with food; do not use as primary prevention in low-risk patients

Paediatric dose

Dose: 5 mg/kg
Route: oral
Frequency: once daily
Max: 100 mg/day (Kawasaki), 75 mg/day (antiplatelet)
Kawasaki disease: 30–50 mg/kg/day in acute phase (max 4 g/day); reduce after fever resolves; AVOID in viral illness in children <16 years (Reye's syndrome)

Dose adjustments

Renal

Use with caution if eGFR <30 ml/min

Hepatic

Avoid in severe hepatic impairment (haemorrhagic risk)

Paediatric weight-based calculator

Kawasaki disease: 30–50 mg/kg/day in acute phase (max 4 g/day); reduce after fever resolves; AVOID in viral illness in children <16 years (Reye's syndrome)

Clinical pearls

  • Irreversible COX-1 inhibition — effects last 7–10 days (platelet lifespan)
  • ASPREE trial: primary prevention in elderly — more harm than benefit (bleeding > cardiovascular benefit)
  • Aspirin resistance: up to 25% of patients (CYP2C19 polymorphism, compliance, drug interactions)

Contraindications

  • Active peptic ulcer
  • Haemophilia and other bleeding disorders
  • Allergy/NSAID-induced asthma
  • Children <16 years for viral illness (Reye's syndrome)

Side effects

  • GI bleeding/ulceration
  • Dyspepsia
  • Bronchospasm (aspirin-sensitive asthma)
  • Tinnitus (high dose)
  • Rare: intracranial haemorrhage

Interactions

  • NSAIDs (increased bleeding/gastropathy)
  • Warfarin/DOACs (increased bleeding)
  • SSRIs (increased GI bleed)
  • Methotrexate (reduced clearance)

Monitoring

  • Signs of GI bleeding
  • Blood pressure
  • Renal function (if CKD)

Reference: BNFc; BNF 86; NICE NG185; AHA guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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