Not Cool, Bro(methalin)

Bromethalin is like some relentless, vicious psycho-killer

Published: April 24, 2017
Meme by Dr. Tony Johnson

“I didn’t think rat poison would hurt my dog – he’s not a rat!”

- Random ER client years ago whose dog was bleeding out due to rat poison

As far as poisons go, most pet owners are aware of a few. There’s your antifreeze (bad – real, real bad), your chocolate (not that bad – unless it’s dark or baking chocolate, then it’s a tasty terror) and that’s about it.

Oh, there are a few that know about rat poison, probably because it’s got poison right there in the name, which is a dead giveaway. (Unless you’re French, I guess, and bad at spelling, in which case you’re mayhap thinking I’m talking about a rat poisson or ratfish, which are kinda gross but not toxic.)

In any case, rat poison isn’t all the same. Ten years ago, if you asked a bunch of ER vets how they feel about treating a dog that’d eaten rat poison, you’d probably get responses like: “Bring it – I have the antidote right here in my hot little hand!” Whereas nowadays if you asked them that same question, they’d be more likely to run and hide, shrieking all the way.

What changed?

The government decided to step in and make things all better.

The most common rat poison available for the past several decades (and the most common one that we’d see in the ER) was known as an anticoagulant; it caused the rats and mice (and cats and dogs that also got into it) to bleed to death.

Incidentally, and I honestly don’t know where it came from, but that old saw about making the poisoned rats want to find water and run out of the house and die is not true.

When a dog or cat eats an anticoagulant rat poison, it does the same thing it does to a rat: it knocks out the body’s ability to clot blood. It may take a day or it may take a few days, but eventually they start bleeding. It could be anywhere; lungs, joints, eyes, brain – I’ve seen them bleed from about any place you could name. (Your body is always developing little leaks, and your blood clotting system stops them right away – unless you’ve eaten rat poison.)

This all sounds pretty bad, and it can be. I’ve seen many pets sickened and a few killed by anticoagulant rat poison, but the good news is that it’s very treatable if it’s caught early on before the bleeding begins in one of those bad places. The antidote is vitamin K, and it works quite well. For patients that are bleeding, they may need some extra treatment as well, like a blood transfusion, but the vast majority of dogs (and rarely cats – they’re pretty smart) that ingest anticoagulant rat poison do pretty well with appropriate treatment.

…and then the EPA got involved.

A few years ago, and totally inexplicably,* they decreed that the rat poisons known as second-generation anticoagulants were no good anymore and manufacturers had to stop making them. First-generation anticoagulants are still around and seem to be disappearing from store shelves because they’re not all that effective, but rats and mice are still around and people want to kill them.

Waiting in the wings to take the spotlight was the second-most popular rat poison, bromethalin.

The second-generation anticoagulant rat poisons were bad, but treatable – they’re sort of like Gru from Despicable Me. They could be mean, definitely sinister arch-villain material at times, but essentially, they were okay at the core.

Not so, bromethalin. Bromethalin is evil.

Bromethalin is like some relentless, vicious psycho-killer, resistant to reason, pleas for mercy or a trio of orphan girls (it works if you know your Despicable Me plot points). Bromethalin is a neurotoxin that causes irreversible brain swelling, seizures and paralysis. There is no antidote. And then you die.

If all the cases of anticoagulant rat poison that I’ve treated in my career were instead bromethalin cases, I would’ve had literally thousands of dead pets on my hands instead of just a few.

See? Evil.

What’s a pet owner to do? Here are few tips:

  1. If you have rats or mice and have to kill them (it happens) use a trap. The worst that’ll happen to your dog is a little squoosh on the nose.
  2. If you do use a poison, know what it is, where it is, and make 100 percent certain that your pet or kids can’t get into it. Pets, rats, mice and kids can drag poison out from where it’s originally placed, so make sure it’s secure. Then double check.
  3. Use a pet-proof housing for the poison (pellets aren’t manufactured any more) and consider using a professional service that knows you have pets. They have housings that will decrease the chance your dog will get into it.
  4. If your dog does get into it, get to the veterinarian quickly. Like – fast. Speedy, go-now-don’t-stop-for-a-Big-Gulp-fast. Pronto. The only way to help your dog if they get into bromethalin is to get them to vomit it up, and hope they didn’t absorb enough to cause problems. Your vet can help with the rest of the decontamination process.
  5. If you are headed to the ER or your regular veterinarian for decontamination, make sure you bring the box the poison originally came in with you. This will help them know what they are treating. I can’t overstress how important this step is. Knowing what the poison is is half the battle, and if your dog got into an anticoagulant, you’ll be able to rest that much easier.

I suppose you could also consider laying a bunch of ratfish outside your house in hopes that the rats would all go out there and hang out with them and eat them and stuff. That might work. In any case, it’s better and safer than having that psycho killer bromethalin around. That stuff is bad.

Did I mention that it’s evil?

*Okay, so not totally inexplicably. Second-generation anticoagulants are responsible for wildlife deaths and poisoning children. Any kind of rat poison for home use must now be sold in block or paste forms that fit inside a bait station designed to prevent kids and dogs from getting into it (which doesn’t mean the more determined ones can’t). Pelleted poison that you just toss on to the ground is no longer allowed because of risks to kids, pets, and wildlife.


Dr. Kendall Harr
June 29, 2017

Hello,  Having done a couple of years worth of research on second generation anticoagulation rodenticides, this article is somewhat misrepresentative of the threat that they pose.  There is very good reason that they are both now illegal in Canada and the US (except for agricultural purposes).  The half lives of these compounds is >300 days sometimes >500 days. So the breakdown if very slow.  They do not just poison one animal, they poison the rat, then they poison the hawk, then they poison the hawk chicks, then they poison, the next predator day after day, week after week, month after month.  They literally can cause local predator annihilation and they are responsible for severe population declines of several birds of prey, owls, etc.  Just because bromethalin is not treatable in dogs does not make it better.

PJ Tonkin
May 10, 2017

The article is not critical of the decision, just a very strong warning about how lethal bromethalin is.

Steven Goats
April 28, 2017

Just read the last paragraph.

Ann Viera
April 24, 2017

I would like to know why EPA made the change about rat poison referred to in the article.  The evidence behind their decision.  It isn't helpful to criticize w/out providing the evidence/reasoning.

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