What is the management for anticoagulant rat poison (rodenticide) ingestion?

Management of Anticoagulant Rat Poison (Rodenticide) Ingestion

For patients with unintentional ingestion of less than 1 mg of long-acting anticoagulant rodenticide (LAAR) active ingredient, observe at home without laboratory monitoring; for ingestions of 1 mg or more, evaluate coagulation studies at 48-72 hours post-exposure; and for symptomatic patients or those with intentional ingestion, refer immediately to the emergency department. 1

Initial Triage and Risk Stratification

Immediate Emergency Department Referral Required:

• Any suspected self-harm, abuse, misuse, or malicious administration regardless of reported dose 1
• Any symptoms of anticoagulant poisoning (bleeding, bruising, hematuria, hematemesis, melena) regardless of dose 1
• Chronic or repeated ingestions for evaluation of intent and coagulopathy 1
• Patients already on therapeutic anticoagulation (warfarin, DOACs) who ingest any amount of rodenticide 1

Safe Home Observation:

• Unintentional ingestion of <1 mg active ingredient in asymptomatic patients 1
• This includes virtually all unintentional pediatric exposures in children under 6 years 1
• Pregnant patients with unintentional exposure <1 mg should follow up with their obstetrician as outpatient, not requiring immediate ED evaluation 1

Outpatient Monitoring Required:

• Unintentional ingestion of ≥1 mg active ingredient in asymptomatic patients requires coagulation studies at 48-72 hours post-exposure 1
• Baseline prothrombin time (PT/INR) should be obtained, then repeated at 48-72 hours 1

Decontamination

Do not perform gastrointestinal decontamination with ipecac syrup or gastric lavage 1

Do not delay transportation to administer activated charcoal 1

For dermal exposures, wash skin with mild soap and water 1

Laboratory Evaluation

Measure prothrombin time (PT/INR) as the primary screening test at 48-72 hours after exposure for at-risk patients 1, 2

Specific coagulation factor analysis (factors II, VII, IX, X) shows profound decreases lasting at least 43 days post-ingestion in significant poisonings 3

Brodifacoum levels can be measured using specialized assays and may guide duration of therapy, with levels below 10 μg/L associated with normal coagulation profiles after vitamin K completion 4

Vitamin K Treatment Protocol

When NOT to Give Vitamin K:

Do not administer vitamin K prior to evaluation for coagulopathy in asymptomatic patients with unintentional exposures 1

When to Initiate Vitamin K:

Begin vitamin K therapy only after documented coagulopathy (elevated PT/INR) or in symptomatic bleeding patients 1, 2

Dosing Regimen:

High-dose oral vitamin K (100 mg daily) is the preferred route and dose for significant brodifacoum poisoning 4, 3, 5

• Oral administration is effective and preferred over subcutaneous or intramuscular routes 3, 5
• Doses up to 100 mg per day have been used without complication 3
• Some protocols use approximately 7 mg/kg per 24 hours divided every 6 hours 5
• Intravenous vitamin K should be given slowly (over at least 30 minutes) if used, as rapid IV injection causes anaphylaxis in 3 per 100,000 patients 6, 7

Duration of Treatment:

Treatment duration ranges from 3-6 months depending on ingestion severity and brodifacoum elimination kinetics 4

• Brodifacoum elimination half-life ranges from 15-33 days in reported cases 4
• Case 1: 33-day half-life required 6 months of vitamin K 100 mg daily 4
• Case 2: 15-day half-life required 3 months of vitamin K 100 mg daily 4
• Monitor PT/INR regularly during treatment and for several weeks after vitamin K discontinuation 4, 2

Treatment Cessation Criteria:

Consider stopping vitamin K when brodifacoum level falls below 10 μg/L with normal coagulation profile 4

Check PT/INR 48-72 hours after stopping vitamin K to ensure coagulopathy does not recur 4

Management of Active Bleeding

For patients with active bleeding from rodenticide poisoning, administer fresh frozen plasma (FFP) and cryoprecipitate in addition to vitamin K 2

• FFP provides immediate replacement of vitamin K-dependent clotting factors (II, VII, IX, X) 2
• Vitamin K takes a minimum of 1-2 hours for measurable PT improvement and should not be expected to have immediate effect 7
• Four-factor prothrombin complex concentrate (PCC) 25 U/kg can be considered for life-threatening bleeding, though evidence is primarily from warfarin reversal studies 6
• Vitamin K 5-10 mg IV should be added to any reversal strategy to sustain effects of clotting factor replacement 6

Critical Pitfalls to Avoid

Do not assume short treatment duration - superwarfarins like brodifacoum require prolonged therapy (months, not days) due to extremely long half-lives 4, 3

Do not use low-dose vitamin K regimens (10-20 mg) typical for warfarin reversal - brodifacoum poisoning requires much higher doses (100 mg daily) 4, 3, 5

Do not stop vitamin K based solely on normalized PT/INR - rebound coagulopathy can occur; confirm with brodifacoum levels if available or extend monitoring 4

Vitamin K will not counteract heparin - this is specific to vitamin K-dependent factor deficiency 7

Repeated large doses of vitamin K are not warranted in liver disease if initial response is unsatisfactory, as this indicates the condition is unresponsive to vitamin K 7

Special Populations

Pregnant patients with significant exposures require the same treatment approach with high-dose oral vitamin K, as the risk of maternal hemorrhage outweighs theoretical fetal risks 1

Premature neonates are at particular risk from benzyl alcohol preservative in some vitamin K formulations and from aluminum toxicity with prolonged parenteral administration 7

Patients with renal impairment may have altered elimination kinetics requiring extended monitoring 7