Rodenticide Poisoning

Classification & Mechanisms

A. Anticoagulant Rodenticides

1st Generation - Warfarin-type

• Examples: Warfarin, coumafuryl
• Mechanism: Inhibit vitamin K epoxide reductase --> block synthesis of clotting factors II, VII, IX, X
• Half-life: ~42 hours
• Toxicity: Requires large single dose or repeated exposure; onset 12-48 hours
• Single small ingestions in children are almost never clinically significant

2nd Generation - Superwarfarins ("Long-Acting Anticoagulant Rodenticides" / LAARs)

• Examples: Brodifacoum, bromadiolone, difenacoum, diphacinone, chlorophacinone, valone
• Mechanism: Same as warfarin but far more potent and prolonged
• Half-life: Brodifacoum ~120 days - a single ingestion can cause anticoagulation lasting weeks to months
• Clinical features: Unexplained bleeding, prolonged PT/INR ± aPTT with large doses
• Indandione derivatives (pindone, diphacinone, chlorophacinone) have similar clinical profiles
• Important note: superwarfarins are not detected by standard warfarin assays; specific reference lab assays exist

Contamination of synthetic cannabinoids with brodifacoum has caused outbreak clusters of anticoagulant toxicity presenting as unexplained bleeding. - Rosen's Emergency Medicine

B. Non-Anticoagulant Rodenticides

Clinical Approach

History

• Identify the specific rodenticide (packaging is critical)
• Route, quantity, and time of exposure
• Intentional vs. accidental
• Age - pediatric accidental ingestions of anticoagulants are rarely significant

Key Lab Investigations

• PT/INR (baseline, then 12-24 h or 24-48 h post-exposure depending on compound)
• aPTT (elevated with large superwarfarin doses)
• CBC, blood type and screen if bleeding

• Phosphides: ABG, metabolic panel, troponin, CXR (pulmonary edema)
• Yellow phosphorus: LFTs, coagulation panel
• Thallium/arsenic: heavy metal levels, urine analysis
• Bromethalin: clinical diagnosis (no specific assay); neuroimaging for edema
• Barium: serum potassium, ECG

Management

General Principles (All Rodenticides)

1. ABCs first - airway, breathing, circulation
2. Remove contaminated clothing, wash skin with water
3. Contact Poison Control Center / toxicologist immediately
4. Gastric decontamination (activated charcoal, gastric lavage, whole bowel irrigation) - only after toxicologist consultation; limited evidence for mortality benefit

Specific Treatments

Anticoagulant Rodenticides

• Warfarin: No treatment for single small ingestion; vitamin K1 (phytonadione) if INR >2.0
  • Dose: Children 1-5 mg/day PO divided; Adults 20 mg/day PO divided
• Superwarfarins: Activated charcoal if presenting within 1 hour of massive ingestion (100 g or 10:1 charcoal:poison ratio); no role for enhanced elimination
  • Vitamin K1 orally for elevated INR without active bleeding
  • Fresh frozen plasma (FFP) or 4-factor PCC for active bleeding
  • Treatment may be needed for weeks to months given long half-life of brodifacoum

Phosphide Rodenticides (Zinc/Aluminum Phosphide)

• Supportive care (mechanical ventilation, vasopressors)
• Limited evidence for IV N-acetylcysteine, melatonin, vitamin E, magnesium
• Caution: gastric lavage may release more phosphine gas - should be done in well-ventilated setting

Heavy Metals (Thallium, Arsenic)

• Arsenic: BAL/dimercaprol, DMSA (succimer), DMPS (for chronic exposure)
• Thallium: Prussian blue (FDA-approved for thallium poisoning)
• Hemodialysis, continuous renal replacement, or charcoal hemoperfusion can help with thallium and arsenic

Strychnine

• Benzodiazepines (first-line for spasms), propofol for refractory cases
• Airway protection - rapid intubation if necessary
• Minimize stimulation (dark, quiet environment)

Barium

• Aggressive IV potassium replacement
• Cardiac monitoring; hemodialysis for severe cases

Key Points (Rosen's Emergency Medicine)

• Most rodenticide exposures are superwarfarin compounds
• INR must be checked at minimum 2 days after large ingestion
• Vitamin K1 is used for reversal of anticoagulant effect; blood products (FFP/PCC) for active hemorrhage
• Superwarfarin poisoning can masquerade as spontaneous coagulopathy - suspect in any unexplained bleeding, including in synthetic cannabinoid users

Special Situations

• Relay toxicosis: Humans (especially children) can be poisoned by eating animals (birds, dogs) that consumed rodenticide
• Vacor (PNU): This older rodenticide causes a severe autonomic neuropathy + diabetes-like syndrome by destroying islet cells; listed among causes of "other specific types of diabetes" in Harrison's and Goodman & Gilman's
• Yellow phosphorus/liver failure: Auxiliary partial orthotopic liver transplantation (APOLT) has been used as a bridge to native liver recovery in severe ALF