January 2024

Bromethalin Toxicity in Cats

By Dr. Justine Lee, DACVECC, DABT

In today’s VETgirl blog, Dr. Justine Lee, DACVECC, DABT reviews bromethalin poisoning in cats. As anticoagulant rodenticides (ACR) are less commonly seen nowadays (and cats are more resistant to these ACR as compared to dogs), veterinary professionals must be aware of this up-and-coming, common active ingredient found in mouse and rat poisons!

Bromethalin is a neurotoxic rodenticide that is often confused with “b” sounding anti-coagulant rodenticides such as bromadiolone and brodifacoum (which both affect Vitamin K1). However, bromethalin is a lipid soluble rodenticide that results in cerebral edema, increased intracranial pressure (ICP), seizures and death. Bromethalin is rapidly absorbed from the gastrointestinal tract (GIT) and once metabolized, crosses the blood brain barrier (BBB). Bromethalin works directly in the central nervous system (CNS) by uncoupling phosphorylation, which results in intracellular accumluation of sodium (and subsequently, water, which follows sodium) to result in cytotoxic edema and intramyelinic edema.

The most common brand names of bromethalin include:

  • Assault®
  • Clout®
  • Fastrac®
  • Real Kill®
  • Talpirid®
  • Tomcat Mole Killer®
  • Vengeance®

Unfortunately, bromethalin has a narrow margin of safety, particularly in cats. Cats are more sensitive to the effects of bromethalin, and have a very low LD50 (0.54 mg/kg) compared to dogs.

In cats, signs of bromethalin toxicosis can be seen as either acute or chronic. Clinical signs of acute bromethalin toxicity can be seen within 2-24 hours, with signs generally developing within 8-12 hours after ingestion; that said signs have been observed as early as 2-4 hours.

Acute bromethalin syndrome
Clinical signs of acute bromethalin toxicosis in cats include:

  • Agitation
  • Weakness/depression
  • Abnormal behavior/mentation
  • Ocular changes (e.g., pupillary light reflex changes, aniscoria, nystagmus
  • Ataxia
  • Blindness
  • Pelvic limb ataxia
  • Fine muscle tremors
  • Hyperexcitiability
  • Hyperesthesia
  • Seizures
  • Coma
  • Death secondary to hypoventilation
Bromethalin toxicity cat VETgirl lateral

Photo courtesy of Dr. Heidi Fay

Chronic bromethalin syndrome
Clinical signs of chronic bromethalin toxicosis in cats occur when a large dose is ingested (e.g., at the LD50) or when sublethal doses are repeatedly ingested (e.g., multiple doses ingested). Clinical signs can be seen as early as 12-24 hours post-ingestion. In experimental studies in cats, clinical signs between 4-7 days after oral administration of doses as low as 0.45 mg/kg. Clinical signs of chronic bromethalin poisoning in cats includes:

    • Weakness/lethargy
    • Hindlimb ataxia/weakness
    • Paralysis
    • Dull mentation progrssing to coma
    • Death

Treatment for bromethalin toxicity in cats
Treatment includes early decontamination, prevention of cerebral edema, and symptomatic supportive care. With recent ingestion in an asymptomatic patient, the use of decontamination (e.g., emesis induction, activated charcoal) is warranted. In cats, tubing (orogastrically) activated cahrcoal with a protected airway can be done under sedation/general anethesia. As bromethalin undergoes enterohepatic recirculation, the use of multiple doses of activated charcoal (without a cathartic) can be administered; in cats, the author recommends just one more additional dose 6 hours later (as it is difficult to administer charcoal to cats).

Additional treatment includes:

    • Intravenous fluid therapy
    • Oxygen support
    • Reduction of intracranial pressure via 15-30 degree head elevation and/or mannitol administration IV
    • Anti-convulsant therapy (such as benzodiazepines, phenobarbital, levetiracetam)
    • Symptomatic supportive care
    • Appropriate thermoregulation

Note: The use of intravenous lipid emulsion (ILE) is not recommended for treatment of bromethalin.

Prognosis for bromethalin toxicity in cats
The prognosis for bromethalin toxicosis varies depending on the amount ingested and the severity of clinical signs; however, prognosis is generally fair to excellent with appropriate decontamination and treatment prior to development of clinical signs. However, if clinical signs develop, such as persistent seizures or paralytic syndrome, the prognosis is poor to grave.

When in doubt, the toxic dose should be ingested by calling the ASPCA Animal Poison Control Center for life-saving advice.

You can find a bromethalin calculator on VIN HERE.


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