What are the treatment options for a patient with suspected rodenticide poisoning, particularly those containing brodifacoum or other long-acting anticoagulants?

Treatment of Rodenticide Poisoning (Long-Acting Anticoagulants)

Immediate Triage and Referral

For patients with suspected long-acting anticoagulant rodenticide (LAAR) poisoning, immediate emergency department referral is mandatory if the patient has any bleeding symptoms, intentional ingestion, chronic exposure, or ingestion of ≥1 mg active ingredient. 1

Patients Requiring Immediate ED Referral:

• Any patient with bleeding symptoms (epistaxis, hematuria, hematochezia, bruising, or neurological symptoms suggesting intracranial hemorrhage) regardless of reported dose 1, 2
• All suspected self-harm, abuse, misuse, or malicious administration cases 1
• Any chronic/repeated ingestion pattern 1
• Asymptomatic patients who ingested ≥1 mg of active ingredient (requires coagulopathy evaluation at 48-72 hours) 1
• Patients already on therapeutic anticoagulation who ingest any dose of LAAR 1

Patients Safe for Home Observation:

• Unintentional ingestion of <1 mg active ingredient in asymptomatic patients (includes virtually all unintentional pediatric exposures in children <6 years) 1
• No laboratory monitoring required for this group 1

Antidote Therapy: Vitamin K1 (Phytonadione)

High-dose oral vitamin K1 is the definitive treatment for LAAR poisoning, with doses ranging from 50-100 mg daily for prolonged periods (months), guided by coagulation studies and brodifacoum levels when available. 3, 4

Dosing Strategy:

• Initial dose: 2.5-25 mg orally, up to 50 mg for severe coagulopathy 5
• Maintenance dose for brodifacoum poisoning: 50-100 mg daily based on case reports of successful management 3, 4
• Duration: Typically 3-6 months for significant brodifacoum ingestions 3, 4
• Do NOT administer vitamin K prophylactically before coagulopathy is documented 1

Monitoring Parameters:

• Check INR/PT at 48-72 hours post-exposure for at-risk patients 1
• Recheck INR 6-8 hours after vitamin K administration 5
• If INR not corrected in 12-48 hours, repeat the dose 5
• Continue monitoring coagulation studies throughout treatment 5
• Target brodifacoum level <10 μg/L before discontinuing therapy (when levels available) 4

Critical Pharmacokinetic Considerations:

• Brodifacoum has a terminal half-life of 15-33 days (up to 60 times longer than warfarin) 3, 6, 4
• Coagulant effects of oral vitamin K take 1-8 hours to manifest 5
• Avoid oral route if gastrointestinal absorption is compromised 5
• Bile salts must be co-administered if biliary secretion is deficient 5

Acute Hemorrhage Management

For patients with active bleeding, immediate administration of fresh frozen plasma or prothrombin complex concentrate is necessary while awaiting vitamin K effect. 6

• Vitamin K alone is insufficient for acute hemorrhage control 5, 6
• Whole blood or component therapy required for severe bleeding 5
• Intracranial hemorrhage has been reported and is potentially fatal 2, 6

Decontamination

Gastrointestinal decontamination with ipecac or gastric lavage is NOT recommended. 1

• Do not delay ED transport to administer activated charcoal 1
• For dermal exposure: wash skin with mild soap and water 1
• Critical pitfall: One fatal case involved ipecac-induced emesis precipitating subarachnoid hemorrhage in a coagulopathic patient 6

Special Populations

Pregnant Patients:

• Unintentional exposure <1 mg: outpatient obstetric follow-up (no immediate ED referral needed) 1

Patients on Therapeutic Anticoagulation:

• Baseline PT/INR immediately, repeat at 48-72 hours 1
• Higher risk for bleeding complications 1

Common Pitfalls to Avoid

• Never underestimate duration of treatment required: Cases require 3-6 months of high-dose vitamin K 3, 4
• Do not stop vitamin K based solely on normalized INR: Coagulopathy recurs when vitamin K discontinued prematurely due to extremely long brodifacoum half-life 3, 6
• Suspect superwarfarin poisoning in unexplained vitamin K-deficient coagulopathy: Brodifacoum is 200-fold more potent than warfarin 3, 6
• Avoid procedures that induce vomiting in potentially coagulopathic patients: Risk of precipitating catastrophic hemorrhage 6
• Recognize that overzealous vitamin K therapy may restore prothrombotic conditions: Keep doses as low as effective 5