Warfarin
Warfarin
Mechanism of toxicity
Toxic dose
Symptoms and signs of poisoning
Special investigations
Management
Antidote
Monitoring
Mechanism of toxicity
Inhibits clotting factors II, VII, IX and X cause significant prolongation of INR.
Toxic dose
Highly variable.
Symptoms and signs of poisoning
Bleeding is the main risk: epistaxis, bleeding gums, ecchymosis, haematochezia, haematuria, menorrhagia, haemarthrosis, bleeding from minor trauma. Severe toxicity: intracranial haemorrhage, retro-peritoneal haemorrhage, gastrointestinal bleed.
Special investigations
INR: may be normal up to 48 hours after ingestion; repeat 24-48 hours post-ingestion or when symptomatic.
Management
Note general principles of acute poisoning.
| Intervention | Not effective | Consider | Indicated |
| Gastric lavage | |||
| Early (within 1 hour) post-ingestion activated charcoal | |||
| Multiple dose activated charcoal | |||
| Whole-bowl irrigation | |||
| Dialysis | |||
| Charcoal haemoperfusion |
Antidote
- Vitamin K1 (Parenteral dosing may be used in patients with active bleeding)
- Dose: 10 mg (adult), 1 to 5 mg (children)
- Therapeutic response may take 4-6 hours.
- Blood products (actively bleeding).
- Fresh frozen plasma, prothrombin complex concentrate, or factor VIIa until bleeding is controlled.
Monitoring
INR: serial testing may be required as INR may not increase for several days.