Rodenticides or “rat poisons” are mixed compounds used to eradicate rodents. They are one of the most toxic agents commonly found in households. Historically, heavy metals such as arsenic were the first agents used to control rodent populations, but the most common rodenticide used in the twenty-first century is anticoagulants.[1] When a clinician suspects rodenticide poisoning, every effort should be made to identify the substance, including package information (i.e., brand name, chemical name, signal word, presence of skull or crossbones on the label) and description (odor, appearance, color). This step may involve staff returning to the point of potential exposure where the patient was last seen and searching for evidence of the rodenticide. In cases of serious ingestion, poison control and/or a medical toxicologist should be contacted.
Given the wide array of toxins used as rodenticides, symptoms will vary depending on the toxin ingested. Rodenticides are often categorized on their label regarding toxicity.[2]
“Danger” or highly toxic rodenticides include thallium, sodium monofluoroacetate (fluoroacetate), strychnine, zinc phosphide, aluminum phosphide, elemental phosphorus, arsenic, barium carbonate. Rarely used or banned dangerous toxins: tetramethylene disulfotetramine (TETS, tetramine), aldicarb, alpha-chloralose, and pyrinuron.
“Warning” or toxic rodenticides include alpha-naphthyl thiourea (ANTU), and cholecalciferol.
“Caution” or less toxic rodenticides include anticoagulants (superwarfarins, warfarin), norbormide, bromethalin, and red squill.
According to the 2017 Annual Report of the American Association of Poison Control Centers, there are almost 10,000 ingestions annually in the United States.[1] Of these, over half of the exposures are in children under six years of age except strychnine and zinc phosphide. Anticoagulants were the most common cause at 5,186 cases reported with 182 of those cases due to warfarin-type rodenticides. The second most common rodenticide was bromethalin at 1,196 cases reported.[1] The outcomes were generally benign. Seven cases noted major outcomes and only two deaths were reported.
The clinical presentation varies depending on the type of rodenticide ingested. A brief outline with specific pathophysiology and symptoms for common rodenticides follows.
Thallium
Acute exposure:
Chronic exposure:
Fluoroacetamide (Compound 1080), Sodium Monofluoroacetate (SMFA)
Symptom onset: 30 minutes to 20 hours
Late complications
Strychnine
Symptom onset: 10 to 20 minutes
Zinc and Aluminum Phosphide
Symptom onset: 30 minutes
Elemental Phosphorus
Arsenic
Symptom onset: 1 to 3 hours
Barium Carbonate
Symptoms:
Tetramethylene Disulfotetramine (TETS, Tetramine)
Symptom onset: 10 minutes to 13 hours
Aldicarb
Symptoms:
Alpha-chloralose:
Pyriminil, Pyriminil, N-3-pyridylmethyl-N-p-nitrophenyl Urea, PNU
Symptoms:
Cholecalciferol (Vitamin D3)
Anticoagulants (Superwarfarin, Warfarin)
Symptoms:
Norbormide
Bromethalin
Red Squill (Urginea maritima)
Symptoms:
Patients most often presenting with rodenticide poisoning are children with oral ingestion. The most common rodenticide used in the United States is a long-acting anticoagulant. The presenting symptoms include hematuria, hemoptysis, epistaxis, flank pain, easy bruising, or petechiae under the blood pressure cuff. Other cases include adults with the intention of suicide. Regardless, the most crucial part of history is identifying the substance ingested. The toxicity is categorized by the amount of poison needed to cause death in 50 percent of those exposed, known as lethal dose 50 or LD50. In some regions, including the United States, this toxicity is denoted by signal words on product labels: danger, warning, and caution.
Physical findings of rodenticides categorized by systems include:
Please refer to the pathophysiology section for a more detailed description of specific rodenticide symptoms.
Assuming unknown ingestion, the clinician may order the following tests. Rodenticides are noted for associated abnormalities but are non-specific.
Initial Care
Immediate management consists of supporting the airway, breathing, and circulation. Once the patient is stable and if visibly contaminated, then the next step involves removing clothes and irrigating skin with water. Gastric lavage and activated charcoal are not indicated in acute poisoning, according to the American Academy of Toxicology.[21] There is limited data that shows a decrease in morbidity and mortality. If the patient presents within 30 to 60 minutes since ingestion, please call poison control immediately for the most updated guidelines.
Acute gastrointestinal effects may benefit from anti-emetics and rehydration to help correct electrolyte derangements. Initiate cooling mechanisms such as evaporative cooling if severely hyperthermic such as in strychnine poisoning. Cholinergic toxicity may benefit from the administration of anticholinergic agents such as atropine, glycopyrrolate, and pralidoxime. Further treatment is often mainly supportive.
Specific Medical Treatment
Renal replacement therapy
Benzodiazepines
British anti-Lewisite
Meso-2,3-dimercaptosuccinic acid (DMSA) or 2,3-dimercapto-1-propane sulfonate (DMPS)
Sodium sulfate or magnesium sulfate
Nicotinamide (intravenous)
Mineralocorticoids
Digoxin immune fab
Most importantly, clinicians should evaluate and manage patients in consultation with regional poison control or a toxicology resource.
Prognosis depends on the specific rodenticide ingested as well as the amount. In general, a better prognosis is associated with early initiation of treatment; however, chronic exposure will have a longer recovery.
Complications include:
Although meant to harm rodents, rodenticides are also toxic to humans, as described previously. A variety of sequelae can lead to organ failure and even death. One should always follow label instructions and take steps to avoid exposure. All rodenticides should be kept out of reach of children and pets, whether they are in use or storage. Children may find rodenticides to be visibly appealing in addition to their taste.
For this reason, tamper-resistant bait stations should be employed to prevent accidental ingestion. When disposing dead rodents into secure bins, always use gloves to avoid contact with their carcass. It is reasonable to seek medical evaluation even if asymptomatic or with mild symptoms like nausea as it can be an early manifestation of severe illness.
Managing rodenticide toxicity requires an interprofessional team, including the emergency department, poison control, toxicologist, neurologist, intensivist, and possibly a nephrologist or hepatologist. The initial management includes a primary survey with the ABCDE protocol. If within one hour of ingestion, gastric lavage and activated charcoal may be used after proper dermal exposure and decontamination. A collective team effort will provide the most expedient care yielding the best prognosis. Those with minimal symptoms may recover fully with treatment, but others with severe toxicity may have permanent organ damage, or their case may even result in death. [Level 5]
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