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Antiplatelet — ACS / Ischaemic Stroke Pregnancy: Avoid in third trimester; low-dose aspirin used in pre-eclampsia prevention under specialist supervision

Aspirin (Loading Dose)

Brand names: Aspirin (generic), Disprin

Adult dose

Dose: 300 mg (ACS or ischaemic stroke loading); 75 mg daily (maintenance)
Route: Oral (chewed or dispersed in water for fastest absorption)
Frequency: Single loading dose; then 75 mg once daily
Max: 300 mg loading dose
NICE NG185 (ACS): 300 mg aspirin as soon as ACS suspected — chewed or dispersed for rapid buccal absorption. Ischaemic stroke / TIA (NICE NG128): 300 mg immediately after CT confirms no haemorrhage

Paediatric dose

Dose: Seek specialist opinion N/A/kg
Route: Oral
Frequency: Seek specialist opinion
Max: Seek specialist opinion
Avoid in under 16s due to Reye syndrome risk; Kawasaki disease is a specialist exception

Dose adjustments

Renal

Use with caution in renal impairment — avoid regular use if eGFR under 10

Hepatic

Avoid in severe hepatic impairment and hypoprothrombinemia

Paediatric weight-based calculator

Avoid in under 16s due to Reye syndrome risk; Kawasaki disease is a specialist exception

Clinical pearls

  • Chewing or dispersing aspirin in water achieves buccal absorption — onset 5-10 minutes versus 30+ minutes for swallowed tablet; critical in ACS
  • CT head mandatory before aspirin in stroke — giving aspirin in haemorrhagic stroke dramatically worsens prognosis
  • NICE NG185: Do not give clopidogrel loading in pre-hospital unless STEMI confirmed — aspirin alone initially is safer without confirmed diagnosis
  • Aspirin hypersensitivity (aspirin-exacerbated respiratory disease, AERD): occurs in approximately 10% of adult asthmatics; use P2Y12 inhibitor alone if aspirin genuinely contraindicated
  • Irreversible COX-1 inhibitor — antiplatelet effect lasts platelet lifetime (7-10 days); reversal requires platelet transfusion if urgent surgery needed

Contraindications

  • Active GI bleeding
  • Haemorrhagic stroke (CT must exclude before giving in stroke)
  • Aspirin allergy / NSAID hypersensitivity
  • Severe hepatic impairment
  • Children under 16 (Reye syndrome)

Side effects

  • GI upset and bleeding
  • Bronchospasm (aspirin-exacerbated respiratory disease)
  • Tinnitus and hearing loss (overdose)
  • Prolonged bleeding time

Interactions

  • Other antiplatelet agents (additive bleeding risk)
  • Anticoagulants (increased bleeding)
  • Ibuprofen (may reduce aspirin's irreversible COX-1 inhibition — take aspirin first)
  • Methotrexate (increases methotrexate toxicity)

Monitoring

  • Bleeding signs
  • GI symptoms

Reference: BNFc; BNF 90; NICE NG185 (ACS); NICE NG128 (Stroke/TIA); BNF 90. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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