ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Antiplatelet — COX-1 Inhibitor Pregnancy: Avoid in third trimester — premature ductus arteriosus closure; low-dose aspirin used in first/second trimester for pre-eclampsia prevention (different indication)

Aspirin (Orthopaedic VTE Prophylaxis)

Brand names: Aspirin 75 mg, Aspirin 150 mg

Adult dose

Dose: 75–150 mg once daily
Route: Oral
Frequency: Once daily
Max: 150 mg/day
Used for extended VTE prophylaxis following initial LMWH period after total hip and knee arthroplasty. NICE NG89: 75–150 mg daily aspirin is an option for VTE prevention (typically after 1–2 weeks of LMWH). Take with food.

Paediatric dose

Route:
Avoid in children <16 years (Reye's syndrome risk)

Dose adjustments

Renal

Use with caution in renal impairment — NSAIDs reduce renal blood flow; antiplatelet doses are generally safer than analgesic doses

Hepatic

Avoid in severe hepatic impairment — bleeding risk from coagulopathy

Clinical pearls

  • EPCAT II trial (NEJM 2018): aspirin non-inferior to rivaroxaban for symptomatic VTE prevention after THR/TKR in low-VTE-risk patients following initial 5-day LMWH — practice-changing for orthopaedics in North America
  • NICE NG89 UK guidance: aspirin 75–150 mg is an option for extended prophylaxis following arthroplasty — commonly used as weeks 2–6 after THA (following 14 days LMWH)
  • Aspirin-sensitive asthma: all NSAIDs and aspirin are contraindicated — present in 8–20% of adult asthmatics; screen before prescribing
  • Pre-operative management: patients on long-term aspirin (cardiac/stroke prevention) — generally continue peri-operatively for THA/TKR; assess bleeding vs thrombotic risk with surgeon and anaesthetist
  • Lower cost and oral administration make aspirin attractive for extended prophylaxis vs LMWH injections — patient preference and compliance benefit

Contraindications

  • Active peptic ulceration
  • Haemophilia and other bleeding disorders
  • Aspirin hypersensitivity / aspirin-induced asthma
  • Children under 16 years (Reye's syndrome)
  • Third trimester of pregnancy

Side effects

  • GI irritation, dyspepsia, peptic ulceration
  • Bronchospasm in aspirin-sensitive asthma
  • Tinnitus (at high analgesic doses — not at antiplatelet doses)
  • Increased surgical bleeding (especially if not withheld pre-op)

Interactions

  • Ibuprofen — competitive COX-1 blockade; ibuprofen taken 2 hours before aspirin prevents antiplatelet effect
  • Warfarin and DOACs — additive bleeding risk
  • Uricosurics (probenecid, benzbromarone) — aspirin blocks uricosuric effect

Monitoring

  • GI symptoms
  • Renal function in at-risk patients
  • Platelet function (not routinely required at prophylactic doses)

Reference: BNFc; BNF 90; EPCAT II Trial (NEJM 2018); NICE NG89; AAOS VTE Prevention Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways