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Bromethalin: not all blue-green rodenticides are the same

In 2008, the Environmental Protection Agency announced that it planned to restrict sales of certain rodenticides containing second-generation anticoagulants (such as brodifacoum and bromadiolone) to pest control professionals and agricultural supply stores only. Rodenticide manufacturers came up to speed with compliance in 2011, and  in doing so, began using bromethalin more and more instead of anticoagulants in their products. 

While the change was designed to make rodenticides safer for our children, pets and wildlife, there has also been some devastating consequences. Unlike anticoagulant rodenticides, bromethalin does not have an antidote, and there are still many people and veterinarians that are not aware of its toxicity. There has been an uptick in the number of cases treated since these regulations have been put in to place, and this toxicity is once again being highlighted in veterinary publications in hopes of raising awareness.  

If a dog had ingested a rodenticide in the recent past, it was very likely a D-Con-like product. Anticoagulant toxicities are relatively easy and cheap to treat if caught early as  there is a 2-5 day lag time before bleeding actually happens. This type of exposure can also be diagnosed with a simple blood test, known as a PT test, which checks the clotting time of the blood and confirms exposure if it was not witnessed.

This is not, however, the case with bromethalin.  Bromethalin is a neurotoxin which affects the cells in the brain by causing a rapid influx of sodium particles into its cells.  When this happens, body water follows the sodium particles and leads to swelling in the central nervous system. The symptoms come on much faster and neurological signs can be seen within as little as 2 hours of ingestion. These signs can include depression, a “drunken” gait, rigid limbs, seizures and coma. Because there is no antidote, treatment is aimed at decontamination, intensive, and expensive hospitalization for support of the body and treatment of clinical signs if they develop.

I am sure many people are thinking, “Who would keep this stuff around when you have pets?!” I often have the same thought, but you would be surprised by the number of dogs we treat for this toxicity.

Here is the take home message: 

  • Severity of signs are dose-dependent, and if the poisoning is discovered within 30 minutes to an hour of ingestion, you should attempt to induce vomiting at home* if you are not close to a veterinarian; this will lessen the amount in the body, and therefore lessen the severity of signs
  • Despite how little was ingested, always assume worst case scenario: your pet should be hospitalized on IV fluids for at least 24 hours, during which time multiple doses of charcoal will be given as well as treating for any brain swelling that develops
  • Always bring in any packaging to your veterinarian to help facilitate rapid treatment
  • The lowest average lethal dose of bromethalin for dogs is 2.38 mg/kg, meaning a 10 pound dog could die from ingesting 5 small cubes of bait- not an uncommon feat
  • If at all possible, avoid the use of any rodenticide if you have pets or children

 

* If you need to induce vomiting at home, you can administer 1 ml of hydrogen peroxide per 1 pound of body weight with a maximum of 45 ml being given. For example, a 10 pound dog would need 10 ml of hydrogen peroxide and 80 pound dog should get no more than 45 ml. Trying this at home is not without risk and there are words of caution to consider: ONLY attempt to induce vomiting if your pet is very alert and if you are further than 1 hour away from your veterinarian.  Also, do not "force" the peroxide in—your pet needs to swallow the peroxide, and because it tastes bad, there is a risk of your pet aspirating the peroxide into the lungs if they are resisting and it is being forced.  Another concern is the potential for aspiration during the vomiting process. Aspiration of peroxide during administration or through the process of vomiting leads to additional problems such as pneumonia. Another note: don't waste time waiting to see if your dog will vomit... gently give the peroxide, grab a blanket to cover your car seat, and begin driving immediately to your vet. 

 

 

 

 

 

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Veterinarian Shea Cox has enjoyed an indirect path through her professional life, initially obtaining degrees in fine arts and nursing. She later obtained her veterinary medical degree from Michigan State University in 2001 and has been practicing emergency and critical care medicine solely since that time. In 2006, she joined the ER staff at PETS Referral Center in Berkeley and cannot imagine a more rewarding and fulfilling place to spend her working hours. In her spare time, she loves to paint, wield her green thumb, cook up a storm and sail. Her days are shared with the three loves of her life: her husband Scott and their two Doberman children that curiously occupy opposite ends of the personality spectrum.

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