Clinical presentation

The main clinical effects of warfarin poisoning are anticoagulation and bleeding complications.

Warfarin inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) and the antithrombotic factors protein C and protein S. In poisoning, the onset of anticoagulation is delayed and depends on the half-life of these clotting factors. The INR rises 12 to 24 hours after ingestion in correlation with a decrease in concentration of factor VII, which has the shortest half-life (6 hours).

The risk of bleeding complications depends on the patient’s INR and pre-existing medical conditions. Anticoagulation can lead to the following bleeding complications:

• intracranial haemorrhage—altered conscious state, focal neurological signs and symptoms
• gastrointestinal haemorrhage—haematemesis, melaena, rectal bleeding, retroperitoneal bleeding (may present as abdominal pain)
• genitourinary haemorrhage—haematuria
• pulmonary haemorrhage—haemoptysis, dyspnoea
• haemorrhagic shock secondary to massive haemorrhage
• external signs of bleeding—bruising, epistaxis, bleeding gums.