Bromethalin Poisoning

Eager, happy dogs like Catherine and Joni will dive into most rodenticides because they taste really good, and not just to rats!


Rat poison just got a whole lot more dangerous.

Bromethalin causes swelling of the brain (cerebral edema) leading to lethargy (inactivity), ataxia (unstable walking), pupils that may be both unresponsive to light and different sizes, loss of consciousness, tremors (shaking), seizures and death. Once significant brain swelling occurs treatment may be futile, as the damage may be irreversible.

As if that were not enough bad news, the onset of action of bromethalin is very rapid.  Therefore, the time between ingestion and initiation of treatment must be very short if the patient is to be saved.

And, that danger is the same for children as for pets.  And wildlife.

Bromethalin, a rodenticide that works by attacking the nervous system, has no antidote. There is no specific treatment. There is no laboratory test for this mouse poison. Your pet’s doctor’s response is limited to evacuation of the toxin (inducing vomiting) and symptomatic, supportive therapy, including IV fluids, diuretics and osmotics that can reduce brain swelling and anticonvulsants if seizures occur.

Bromethalin looks a lot like brodifacoum, an anticoagulant rodenticide. Both are extruded pellets and both are green. Bromethalin is a darker, turquoise color and brodifacoum is a bright green.

The names even look a little bit alike to the untrained.

Because brodifacoum is a long-acting anticoagulant (LAAC), poisoning by ingesting it can be treated with medications to allow the blood to clot again (to read more about brodifacoum click here). Transfusions can also be utilized in patients with severe blood loss.

Click here to read Part Two of this ongoing controversy.

See you next week, Dr. Randolph.

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Dr. Randolph
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  1. I have an 80 mini pig male approx 1 yr old. He ate 3 blocks of this tomcat rat poison. Approx 24 to 36 hours ago. My pig vet is on vacation and I have watched him closely and he has not exhibited any signs of poisoning. I am worried about cerebral edema. How long till he is out of the woods for this to happen? I belive each block has .01% bromethalin

  2. My American Strafford terroir, Trouble ate Tom cat mouse bait…vet induced vomiting and gave him charcoal… poison control said the tab he ate was 1oz, he weighs 77lbs…they seem to think he will be fine because by his weight they figure 3oz to be fatal. What can I do besides sit here and wait for him to have complications?

  3. My little dog died suddenly four weeks ago today. She seemed fine all night, sitting in the chair with my mom for six hours. She has always been a finicky eater and my mom cooks for her, so she had eaten some pork chop that night, but refused her dry food. She did this sometimes. At bedtime, she ran up the stairs and begged for her treat as usual and ate it all. Everything was normal. About half hour later, she whined to get out of her playpen. I noticed she was panting hard, so I turned on the air conditioner. I offered her water and she got an unusually long drink. She rubbed her face on the bed, so I looked at her gums and teeth, but they seemed normal. So I cleaned her ears, as she had had an infection some years ago. After I cleaned her ears, she appeared to be in distress. I felt her and found that she was trem bling. At this point, I got dressed to head to the emergency vet. She followed me down the stairs running quickly after me and as I was tying my shoes, I began to hear liquid in her nose and throat and she began to have trouble breathing because of it. I grabbed her and headed for the vet hospital. On the way, she died. It was only a little over half hour from getting her from the playpen till she died. CPR did not revive her. The vet said he found a lot of blood and air in her stomach. No other signs of problems. My breeder’s vet and my vet said it sounded like a pulmonary aneurysm. A few days later, I realized she was exposed to brodifacoum four days earlier, but I checked the traps and did not find any missing. I calculated that she would have to have eaten about an ounce, which would be 1/3 of the bait. It just doesn’t seem to be. She is used to eating roast, chicken, livers, gizzards and pork chops on her dry food. I can’t imagine her eating a dry poison pellet. We neve r saw a speck of blood. No nosebleeds or bruising. She lost her bladder when she died and there was no blood. I turned her upside down when she died to try to get her breathing again… no blood. No lethargy. No symptoms of poisoning. I looked in the playpen. No blood, no stool, no vomit. Nothing. I am driving myself crazy trying to figure out what could have happened to her. I blame myself of course. I had her heartworm tested last spring. Heartguard administration was hit and miss. Could heartworms cause an aneurysm in less than a year? Could she have been poisoned and not shown any bleeding? We had xrays and bloodwork done last spring when she quit eating for two days, and all organs looked normal. Bloodwork was off a little, so we had her tested for Addison’s but it was negative. I have read that aneurysms are rare in dogs. But she didn’t show any symptoms until right up until she died. The vet who tried CPR said without necropsy he would not venture a guess. Without any signs of poisoning or heart worm problems, or any kind of problem whatsoever, is a pulmonary aneurysm the likely cause? But it was 4 days after exposure to poison (my mom took her in the vacant farm house) so I felt that had to be it. But I could not find a bait station with pellets missing. My mom swears she watched her closely and there is no way she got into poison. I am at a loss. It all seem surreal. I am on chemo for an illness and my little dog was my companion. I have no peace, wondering what happened to her. My other little dog is fine. Do dogs have aneurysms in the lungs and just die like that? I hope you can help me with some guess at what happened. We were with them all day and night all the time. I’m sure we would have seen symptoms if any were there. She was a coton de tulear and they don’t have a lot of health issues. That’s why I bought her, after having a lot of vet bills with my two wheatens. I have spent endless hours researching sudden death and find no answers. She was an indoor only dog, six years old. Can you tell me if it sounds like an aneurysm since she had no prior symptoms? I would appreciate anything at all you might be able to add. Thank you. Kelly

    • Kelly, please accept our sympathy on the loss of your precious baby. Do not feel guilty (Click here to read about the stages of grief in pet loss. Blaming one’s self is a necessary step, but do not dwell on it.) Next, there was a miscommunication. What your ER veterinarian said was that she could have died from a pulmonary embolism, not aneurysm. I don’t know what the rate of aneurysm formation is in dogs, but in 33 years of practice I have never diagnosed one. Pulmonary embolism (its full name is pulmonary thromboembolism), on the other hand, is not uncommon in illness. I emphasize “in illness” because it usually is associated with an inflammatory condition of some type, resulting in clots (thrombi) being created, which can obstruct an artery anywhere in the body. In the case of pulmonary embolism the artery is in the lungs. The resulting response of the body is to flood the area with fluid so as to dilute the many bad players that are associated with the pathologic occurrence. That leads to the frothy, sometimes bloody, fluid that we sometimes see coming from the nose and/or mouth. The fact remains that the ER doctor’s statement is absolutely correct: Without a necropsy no answers will be forthcoming. Literally, there are thousands of possible causes of your little dog’s demise. And, pulmonary thromboembolism isn’t a primary problem, it is the body’s inappropriate response to some other condition. All you can do now is move on, when the time feels right to you. Do not get bogged down in your grief (as hard as that is to do. I grieved for our Sally for over 3 years.) With your next pet, be very faithful with her monthly heartworm preventive (click here to read about how to get a free monthly email reminder). Here is a hug sent down the line. We understand your pain and your loss.

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