Bromethalin – a neurotoxicant

Bromethalin is a commonly used rodenticide, but should NOT be confused with brodifacoum and bromadiolone (which are both anticoagulant rodenticides). Bromethalin, a neurotoxic rodenticide, is marketed under several common brand names of Assault®, Tomcat Mole Killer®, Talpirid®, Real Kill®, Clout®, Fastrac®, Vengeance®, etc.

One of the biggest mistakes I see veterinarians making when treating rodenticides is assuming bromethalin is treated with Vitamin K1 as an antidote. Bromethalin works by uncoupling oxidative phosphorylation in the brain and liver mitochondria.1 This results in decreased ATP production, which affects sodium and potassium pumps; as a result, lipid peroxidation occurs, resulting in sodium accumulation within the cell.1 Edema of the central nervous system (CNS) may result.1

In dogs, the LD50 of bromethalin is 2.38-3.65 mg/kg, with a minimum lethal dose being 2.5 mg/kg.1 Cats are more sensitive to the effects of bromethalin, and the LD50 is significantly lower (0.54 mg/kg).1 Clinical signs are dose-dependent, and the onset of clinical signs depends on the amount ingested. Typically, with acute ingestion, signs may be seen within 2-24 hours.1

Rodenticide defecated out by a dog

Rodenticide defecated out by a dog

Clinical signs of bromethalin toxicity include:

  • CNS stimulation or depression
  • Abnormal behavior
  • Ataxia
  • Paresis
  • Hind limb paralysis
  • Anisocoria
  • Nystagmus
  • Changes in the pupillary light reflex (PLR)
  • Tremors
  • Hyperesthesia
  • Seizures
  • Coma
  • Death (rare)

Treatment includes early decontamination (e.g., emesis induction if asymptomatic, followed by charcoal administration), anti-emetic therapy (to prevent aspiration pneumonia), fluid therapy (to perfuse the patient and the central nervous system), prevention of cerebral edema (mannitol, only if clinical signs are severe), and symptomatic supportive care.

With recent ingestion in an asymptomatic patient, the use of decontamination (e.g., emesis induction, activated charcoal) is warranted. As bromethalin undergoes enterohepatic recirculation, the use of multiple doses of activated charcoal (without a cathartic) can be administered q 6 hours for 24 hours. Patients should be monitored for signs of neurotoxicity.

The use of IV fluid therapy, oxygen support, head elevation, mannitol (to decrease cerebral edema), anticonvulsant therapy, and thermoregulation is warranted if clinical signs develop. The prognosis 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. If persistent seizures or paralytic syndrome is seen, the prognosis is poorer.

When in doubt, contact the manufacturer of the rodenticide for free Animal Poison Control advice or ASPCA Animal Poison Control Center at (888) 426-4435 for life-saving advice. You can also download the ASPCA APCC app and calculate the toxic dose for bromethalin here!

ASPCA_animal_poison_control

 

  1. Steve says:

    What are the long term effects of Bromethalin poisoning if decontamination with emesis induction and followed by charcoal administration is started within 1 hour of the dog eating the poison? Kidney, Liver, Heart…?

  2. John says:

    This unfortunately just happened to an 8-week old puppy I was planning to adopt this week (three of them may have been exposed). They believe emesis and charcoal was administered within 2 hours and are continuing the regular charcoal therapy. A second Vet (opinion) recommended vitamin K1 for 30 days although they had the package and clearly confirmed it was Bromethalin.

    Also concerned over any long-term effects so it’s good to see the response above. Is there any downside of giving a puppy 30 days of Vitamin K1 that they may not really need?

    • vetgirl says:

      Vitamin K1 is super safe, so that’s not an issue. You just want to always confirm the active ingredient to make sure the poison is being treated appropriately. Also, know that you ALWAYS get free animal poison control advice by calling the 800-number on the box of poison (in the USA only). Hope that helps!

  3. Michael Correll says:

    I have been sporadically using both Bromethalin and Diphacinone based rat poisons to hold the rat [and mongoose] population down on our property, [as well as slug baits] because of the prevalence of rat lung worm infections in our area. I do apply them in locked bait boxes so that neighbor pets cannot access the bait blocks.
    We acquired a couple of “rat traps” last December from the pound. They are outdoor cats, but are not “barn cats”. The live on the lanai and are fed, watered, handled and socialized daily. They are family. They hunt for sport and fun. Their main toys have been gekos, anoles, and coqui frogs. They are now almost a year old. I just found a rat body on the lawn. They appear to have graduated to the larger prey we intended them for.
    My concern is the danger from their eating rats poisoned with either or both of the rodenticides I have been using.
    Need I worry about it?

    • vetgirl says:

      Relay toxicity (e.g., when a cat eats a dead mouse) is typically rare unless the cats are feral and eating mice daily as part of their routine diet. Cats are also very resistant to diphacinone, but are very sensitive to bromethalin. There is definitely a risk, however, and when in doubt, I recommend contacting the non-profit ASPCA Animal Poison Control Center for life saving advice. When in doubt, mouse traps (snap traps) are more humane and safer for this reason.

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  5. Ashley Webb says:

    Hello. I have a 120lbs pot belly pig. He ate 1 bar of tomcat mouse Bait (at 1pm on 4/30). They are 1oz for each block. Containing 0.01% bromethalin. I gave him 2tbs hydrogen peroxide mixed with coconut water (he would not accept it just plain). He drank it. He has not vomited yet. It has been about 1 hour since the hydrogen peroxide. And about 3 hours since invention of the poison.
    I have been in contact with my vet. He didn’t think that by the time I got him there (vet is a couple hours away) that it would do him much good. So, I am picking up vitamin k1 tomorrow morning. But you are saying that vitamin K1 is not helpful?

    My other question: what is the lethal amount of bromethalin for a 120lbs pot belly pig? He ate a 1oz block. So 28 grams. So 28,000mg. So there is 2.8 mg of bromethalin per block. Correct?

    • vetgirl says:

      Please call ASPCA Animal Poison Control Center directly. Vitamin K doesn’t do anything from bromethalin.

  6. John says:

    If a dog only chews on a poisoned rat carcass and doesn’t swallow it how dangerous might this be to the dog. 20lbs to 115lbs dogs.

    Thanks

    • vetgirl says:

      Relay poisoning is not very common, but when in doubt, we would recommend calling the ASPCA Animal Poison Control Center to be safe.

  7. Jesse Wilmot says:

    Tyson My 1 1/2 old French BullDog Ate about a 1/4 of a TomCat Block Today. We Bought a House. We where cleaning the Apartment out for the Last Time. When Tyson got behind the fridge and found a old block of TomCat. I Totally forgot I had put back there behind the Fridge 3/4 May be Even 5 years ago. I noticed b4 he Really starting Eating it. But he Swallowed a few bites. I Administered hydrogen peroxide right Away. He vomited a lot. 8/10 times puddles of Foam with green still chunky bits of bait. The last 3 times all white foam. He Seems Good. He is a Tough Little Guy. What should I Do Now? Any and All Recommendations Please. Like I Said I just bought a house and do not have $500 to go to the vet. If there is no Need. Of Course Anything For Tyson!! Please Help!!! Thank you

  8. Enrique Hernandez says:

    My German Shepard dog got to a less than 25% of a Tom cat stick ..

    I call my vet he informed me that it’s to late to do anything it’s been more than 3 hours..

    What else could I do for her she is about 6 months about 13 pounds, she still very playful, but seems to rest a little more.

    Any information would be very appreciated..

    It’s been 8hours now ..

    What do I need look out for ..

    Thank you

    • VETgirl says:

      We don’t answer medical queries directly here, but you can call the Tomcat 800 number on the box for 24/7 care immediately!

  10. Kelly says:

    My Yorkie mix chewed on a dead mouse (caught him be4 he ate any)the mouse who ate a lite bit of a tomcat l with bromethalin .01 in it will he my dog be ok? He has ate and pooped 3 times will he be ok?

    • Justine Lee says:

      Highly unlikely to be an issue as that is relay toxicity, but I would recommend calling the 800-# on the box of Tomcat to ask them!

  11. Kay Mason says:

    Just an example one cat’s signs with bromethalin toxicosis. My 12 year cat ate an indeterminate amount of small Tom Cat baits…. green bits over a 2 ft area and 1/3 eaten small bar present. Exposure was 2-4 hours before getting to the referral center ER. My cat has hypertrophic cardiomyopathy and diabetes and is on cardiac meds and insulin. He spent 11 hours in ER and was discharged home with activated charcoal every 8 hours for 36 hours. They administered an iv lipid emulsion once and activated charcoal twice. His heart disease is so advanced they did not give fluids(to risk pulmonary edema), do a gastric lavage( to stress him). They did not want to kill him with the treatment. They did not give him a cathartic. His blood work was normal. The doctor said in his experience if cats made it 12 hours without symptoms then they were usually ok long term. My cat came home looking and acting 100% normal. 6 hours later he ate another dose of activated charcoal mixed with food and had a BM that had green in it ( Tom Cat bait). 8 hours later I woke up to give him another dose of activated charcoal. His respirations were normal and the ate the food/charcoal mix but he was mildly ataxic ( wobbly )on his hind legs. In the morning his ataxia was the same. His ataxia slowly worsened over the day and he appeared to get weaker. He can wobble to his food bowl, water bowl and litter box but he usually ” falls over” in the rear when he is done with whatever task he he is doing. He is asleep now, respirations normal . It has been almost 48 hours since his exposure and his symptoms were first noticed at 2 am, 27 hours after exposure. Since he is cognitively normal and only wobbly in the rear I am waiting to see how he progresses.

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