What are the active ingredients and constituents of commercial rat poisons?

Active Ingredients in Commercial Rat Poisons

Commercial rat poisons contain three primary active ingredients: anticoagulant rodenticides (first- and second-generation), bromethalin, and cholecalciferol (vitamin D3), with anticoagulants being the most common but bromethalin and cholecalciferol exposures increasing since 2011 EPA regulations. 1

Anticoagulant Rodenticides

First-Generation Anticoagulants

• Coumatetralyl is a first-generation anticoagulant that requires multiple feedings over 6 days to achieve complete mortality in rats 2
• These compounds work by inhibiting vitamin K epoxide reductase (VKOR), the enzyme that activates vitamin K, leading to depletion of vitamin K-dependent clotting factors (II, VII, IX, X) 2

Second-Generation Anticoagulants

• Bromadiolone is a second-generation anticoagulant requiring only 4 days of feeding to achieve complete mortality, making it more potent than first-generation compounds 2
• Second-generation anticoagulants have longer half-lives and greater potency, requiring fewer feedings to achieve lethal effects 2

Clinical Mechanism

• Anticoagulant rodenticides cause coagulopathy by depleting vitamin K-dependent clotting factors, leading to prolonged PT/INR and potential bleeding complications 3
• Treatment of anticoagulant rodenticide poisoning involves vitamin K administration: 10 mg IV by slow infusion, with reassessment of INR after 12-24 hours 3
• For life-threatening bleeding from anticoagulant rodenticides, four-factor prothrombin complex concentrate (25-50 U/kg) should be administered along with 10 mg IV vitamin K 3

Bromethalin

Mechanism and Toxicity

• Bromethalin is a non-anticoagulant neurotoxic rodenticide with an LD50 of 2 mg/kg in rats, causing death within 8-12 hours at doses exceeding the LD50 4
• High-dose bromethalin exposure causes clonic convulsions and respiratory arrest, while sublethal or multiple low doses produce hind leg weakness, loss of tactile sensation, and spongy degeneration of white matter due to intramyelinic edema 4
• Bromethalin is metabolized to a desmethyl metabolite, and its toxicity can be modified by microsomal enzyme inducers and inhibitors 4

Regulatory Context

• EPA regulations finalized in 2008 (implemented by June 2011) restricted consumer rodenticide products to first-generation anticoagulants or non-anticoagulants (bromethalin and cholecalciferol), leading to increased bromethalin exposures 1

Cholecalciferol (Vitamin D3)

• Cholecalciferol is a non-anticoagulant rodenticide that has become more prevalent in consumer products since 2011 EPA regulations 1
• Cholecalciferol causes toxicity through hypercalcemia and subsequent organ damage, particularly affecting the kidneys and cardiovascular system 1

Sodium Fluoroacetate (Compound 1080)

Historical and Current Use

• Sodium fluoroacetate was introduced as a rodenticide in the US in 1946 but its use as a general rodenticide was severely curtailed by 1990 due to extreme toxicity to non-target mammals 5
• Currently licensed in the US only for use against coyotes preying on livestock, and in Australia and New Zealand for controlling invasive species 5

Mechanism of Toxicity

• Fluoroacetate combines with coenzyme A to form fluoroacetyl CoA, which substitutes for acetyl CoA in the tricarboxylic acid cycle, producing fluorocitrate that binds tightly to aconitase and halts the cycle 5
• This mechanism impairs oxidative metabolism, reduces ATP production, depletes glutamate (contributing to seizures), causes lactic acidosis, and leads to citrate accumulation with potential hypocalcemia 5

Clinical Presentation

• Acute poisoning presents with nausea, vomiting, and abdominal pain within 1 hour, followed by sweating, apprehension, confusion, agitation, cardiac arrhythmias (both supraventricular and ventricular), QTc prolongation, hypotension, and seizures 5
• Management is purely supportive, including correction of hypocalcemia, as no proven antidotes exist for human use 5

Vacor (N-3-pyridylmethyl N'-p-nitrophenyl urea)

• Vacor is a rodenticide that resembles corn meal in appearance, posing particular risk to small children who may mistake it for breakfast cereal 6
• This compound was associated with multiple pediatric poisoning cases due to its attractive appearance and packaging 6

Common Pitfalls

• Many patients use the term "D-con" to refer to any rodenticide regardless of brand or active ingredient; always verify the specific active ingredient before initiating treatment 1
• The shift in EPA regulations has fundamentally changed the rodenticide exposure landscape, with bromethalin and cholecalciferol now representing a larger proportion of cases than historically 1
• Resistance to anticoagulant rodenticides has developed in some rat populations through VKOR enzyme modifications, though susceptibility remains in many areas 2