Bromethalin is a potent, non-anticoagulant rodenticide classified as extremely hazardous, making it highly toxic to humans and other mammals. This neurotoxin is designed to be lethal in a single feeding for rodents. Accidental or intentional exposure in humans carries a significant risk of severe neurological effects and death. Unlike older anticoagulant poisons, bromethalin targets the central nervous system rather than causing internal bleeding, leading to cellular damage.
Where Bromethalin is Found
Bromethalin is widely available for rodent control in commercial and residential settings. It is commonly found in block baits, pellets, paste, and soft baits, often colored to deter non-target species. Consumer products typically contain a low concentration, around 0.01%, but this still poses a serious risk if ingested.
Its use increased after restrictions on second-generation anticoagulant rodenticides, making it a common replacement product. It is often encountered in residential garages, basements, agricultural structures, or industrial buildings. Professional products may contain slightly higher concentrations, such as 0.025% in mole control baits.
Accidental exposure frequently involves young children ingesting small amounts. Intentional ingestions by adults, however, carry the greatest risk of severe effects or death. Occupational exposure is minimized by required personal protective equipment.
How Bromethalin Affects the Human Body
After ingestion, bromethalin is rapidly absorbed and metabolized in the liver into N-desmethyl bromethalin. This metabolite is the actual toxic agent and is more potent than the parent compound. Both substances are highly lipid-soluble, allowing them to cross the blood-brain barrier and concentrate in the central nervous system.
In the brain, the metabolite disrupts oxidative phosphorylation in nerve cell mitochondria. This prevents the production of adenosine triphosphate (ATP), the primary energy source for cellular functions. The resulting energy depletion inhibits the sodium-potassium pump, which maintains fluid balance across cell membranes.
The pump’s failure breaks down osmotic balance, causing fluid to accumulate inside the myelin sheaths and nerve axons. This fluid accumulation results in widespread swelling of the brain tissue, known as cerebral edema. The increased intracranial pressure damages neuronal axons, leading to the severe neurological signs of poisoning.
Recognizing the Signs of Poisoning
Clinical signs of bromethalin poisoning vary based on the amount ingested and the time elapsed since exposure. Symptoms are often delayed because the toxin must be metabolized and cause cellular damage, sometimes appearing hours or even days later. In severe cases, signs may not fully manifest for up to seven days.
Initial signs of mild exposure often resemble general sickness, including gastrointestinal issues like nausea, vomiting, abdominal pain, and diarrhea. Patients may also report non-specific symptoms such as headache, lethargy, or agitation. Even if these milder signs resolve, medical evaluation is warranted due to the potential for delayed complications.
Significant exposure leads to severe neurological dysfunction caused by cerebral edema. Serious signs include tremors, muscle weakness, loss of coordination (ataxia), and myoclonic jerks. As brain swelling worsens, patients can experience seizures, altered mental status, confusion, and depressed respiration, potentially leading to paralysis, coma, and death if uncontrolled.
Emergency Response and Treatment
Immediate action is necessary if bromethalin ingestion is suspected. The first step is to contact the national Poison Control Center at 1-800-222-1222 for expert guidance. If the exposed person is unconscious or having difficulty breathing, emergency medical services must be called immediately.
There is no specific antidote for bromethalin poisoning; treatment focuses entirely on supportive care and symptom management. If ingestion was recent and the patient is alert, medical staff may administer activated charcoal to limit toxin absorption. Because bromethalin is lipid-soluble and may recirculate, multiple doses of charcoal may be considered.
Management for symptomatic patients centers on controlling severe neurological effects, especially cerebral edema. Medications like mannitol or hypertonic saline are used to draw fluid out of the swollen brain tissue and decrease intracranial pressure. Seizures are controlled using benzodiazepines, such as diazepam or midazolam. Patients who ingested a significant amount require a minimum of 12 hours of observation in a healthcare facility.