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P2Y12 Inhibitor Antiplatelet — ACS Pregnancy: Avoid in pregnancy — limited safety data

Clopidogrel (Loading Dose)

Brand names: Plavix

Adult dose

Dose: 300 mg loading (NSTEMI/UA); 600 mg (STEMI pre-PCI in selected cases)
Route: Oral
Frequency: Single loading dose; then 75 mg once daily
Max: 600 mg loading dose
NICE NG185: Clopidogrel 300 mg loading + aspirin for NSTEMI/UA. STEMI: prasugrel or ticagrelor preferred over clopidogrel if available. Dual antiplatelet therapy (DAPT) for 12 months post-ACS

Paediatric dose

Dose: Not established N/A/kg
Route: Oral
Frequency: Not established
Max: Not established
Not routinely used in paediatrics

Dose adjustments

Renal

No dose adjustment required

Hepatic

Avoid in severe hepatic impairment

Paediatric weight-based calculator

Not routinely used in paediatrics

Clinical pearls

  • Prodrug requiring CYP2C19 activation — poor metabolisers (approximately 30% of population) have reduced antiplatelet effect; prasugrel and ticagrelor do not have this limitation
  • MHRA and ESC: Omeprazole and esomeprazole significantly reduce clopidogrel's active metabolite — use pantoprazole or lansoprazole for gastroprotection in DAPT
  • TTP: rare but life-threatening complication (platelet consumption + microangiopathic haemolytic anaemia) — typically within first 2 weeks; requires urgent haematology review and plasma exchange
  • Clopidogrel vs prasugrel vs ticagrelor in ACS: prasugrel and ticagrelor are more potent and have better outcomes in STEMI (TRITON-TIMI 38, PLATO trials) but higher bleeding risk
  • Stop 5 days before elective surgery (7 days if prasugrel) — to allow platelet function recovery

Contraindications

  • Active pathological bleeding
  • Severe hepatic impairment
  • Hypersensitivity to clopidogrel

Side effects

  • Bleeding (most common serious risk)
  • GI upset
  • Rash
  • Thrombotic thrombocytopenic purpura (TTP — rare but life-threatening)
  • Neutropenia (rare)

Interactions

  • PPIs (omeprazole and esomeprazole reduce clopidogrel activation via CYP2C19 inhibition — use pantoprazole if GI protection needed)
  • Warfarin / DOACs (increased bleeding)
  • Other antiplatelet agents (additive bleeding risk)

Monitoring

  • Signs of bleeding
  • FBC (neutropenia, TTP)
  • Platelet count if TTP suspected

Reference: BNFc; BNF 90; NICE NG185 (ACS); ESC ACS Guidelines 2023; MHRA Drug Safety Update (clopidogrel/PPI interaction). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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