What is the treatment for anticoagulant rodenticide (rat killer) poisoning?

Treatment for Anticoagulant Rodenticide Poisoning

Immediate Assessment and Stabilization

For anticoagulant rodenticide poisoning, prioritize immediate supportive care including airway management and hemodynamic support without waiting for toxin confirmation, contact poison control immediately, and avoid gastrointestinal decontamination in late presentations as it is ineffective once absorption has occurred. 1, 2

• Do not delay supportive care while awaiting rodenticide identification—treatment must begin immediately based on clinical presentation 1
• Gastrointestinal decontamination with ipecac syrup, gastric lavage, or activated charcoal is not recommended in late presentations (beyond 1-4 hours post-ingestion) as these interventions are ineffective once absorption has occurred and may delay definitive care 1, 2
• For dermal exposures, decontaminate by washing the skin with mild soap and water 2

Risk Stratification and Laboratory Monitoring

• Measure INR at 36-48 hours post-exposure for all patients except young children with unintentional ingestion of <1 mg active ingredient 2, 3
• If INR is normal at 48-72 hours, no further action is required even with long-acting formulations 2, 3
• Patients with unintentional ingestion of <1 mg active ingredient (practically all unintentional pediatric ingestions) can be safely observed at home without laboratory monitoring 2
• Patients with unintentional ingestion of ≥1 mg active ingredient who are asymptomatic should be evaluated for coagulopathy at 48-72 hours after exposure 2

Vitamin K Therapy

Do not administer vitamin K prophylactically before coagulopathy is documented—wait for INR results in asymptomatic patients without significant exposure. 1, 2

For Elevated INR Without Active Bleeding:

• If INR is <4.0, no treatment is required 3
• If INR is ≥4.0, administer phytonadione (vitamin K1) 10 mg intravenously (100 mcg/kg for children) 3
• Initial oral dosing for anticoagulant-induced coagulopathy: 2.5-10 mg, up to 25 mg initially; in some cases 50 mg may be required 4
• Evaluate INR after 6-8 hours and repeat dose if INR remains prolonged 4

For Active Bleeding:

• Administer phytonadione 10 mg intravenously (100 mcg/kg for children) immediately 3
• Add prothrombin complex concentrate 50 units/kg, OR recombinant activated factor VII 1.2-4.8 mg, OR fresh frozen plasma 15 mL/kg if concentrate unavailable 3

Long-Term Management Considerations

• Long-acting anticoagulant rodenticides (brodifacoum, bromadiolone, difenacoum) have extremely long half-lives (up to 24-60 days) and high affinity for vitamin K epoxide reductase compared to warfarin 5, 6, 7
• Rebound coagulopathy is common after initial treatment—monitor INR regularly and adjust vitamin K dosing accordingly 6, 7
• Chronic maintenance therapy often requires 100 mg oral vitamin K1 daily, with treatment courses averaging 168 days for significant exposures 7
• Repeated large doses of vitamin K are not warranted in liver disease if initial response is unsatisfactory 4
• Failure to respond to vitamin K may indicate congenital coagulation defect or condition unresponsive to vitamin K 4

Special Populations and Referral Criteria

• Immediately refer to emergency department: suspected self-harm, abuse, misuse, malicious administration (regardless of dose), any symptoms of bleeding/bruising, chronic ingestion, or patients on therapeutic anticoagulation 2
• Pregnant patients with unintentional exposure to <1 mg active ingredient should be evaluated by obstetrician or primary care provider as outpatient (immediate ED referral not required) 2
• Consider medical toxicology consultation for complex presentations 1

Critical Pitfalls

• Avoid overzealous vitamin K therapy—excessive dosing may restore prothrombotic conditions that originally required anticoagulation 4
• Monitor for intracranial hemorrhage in patients with severe coagulopathy, as this is the most common cause of death from LAAR poisoning 6, 7
• Be aware of paradoxical thrombosis and thrombotic complications that can accompany hemostatic therapy 7
• Coagulant effects of vitamin K are not immediate—improvement in INR may take 1-8 hours; interim use of blood products may be necessary for severe bleeding 4