By Pamela Huyck, CVT
Associate Veterinary Information Specialist at Pet Poison Helpline®

There is a lot of incorrect information about mouse and rat poisons (rodenticides) out there.  Here are some of the common misconceptions and explanations as to how they are incorrect.

Mouse and rat poisons won’t harm dogs or cats.

Mouse and rat poisons can harm dogs and cats.  Whether or not a particular product is harmful to your pet will depend on the specific active ingredient, how much your pet ingests compared to how much your pet weighs, your pet’s medical history, and whether or not your pet has ever eaten mouse or rat poison before.  Different poisons cause different signs.  The most common rodenticides cause one of three things: internal bleeding, brain swelling, or hypercalcemia (high calcium level, which can lead to things like kidney failure).  Keep mouse and rat poisons well out of reach of pets.  If the poison comes with a plastic bait station make sure you use the bait station to help deter pets from eating the bait (some pets will still chew through the bait station so it is best to place bait stations out of the reach of pets).

The poison makes the rodents thirsty so they leave the house to find water/The poison dehydrates rodents.

As mentioned above, there are three major things we see with rodenticides, depending on the active ingredient: brain swelling, internal bleeding, or hypercalcemia which can lead to kidney failure.  When pets are experiencing kidney damage they may become thirstier than usual but the increased thirst comes from the kidney damage caused by the poison.  None of the common rodenticides work by dehydrating rodents.

If my pet eats some rodenticide I need to keep him from eating or drinking so that the poison won’t be activated OR
If my pets eats some rodenticide I should feed him or give him milk right away so the food/milk will absorb the poison.

With the exception of the phosphides (which are typically used as mole and gopher poison, not as mouse and rat poison), allowing your pet to eat or drink will not “activate” the poison or keep it from working and keeping your pet from eating or drinking will not save him from the effects of the poison.  If your pet has ingested a toxic dose of poison he will be affected whether or not he eats or drinks afterwards.  The phosphide rodenticides work by producing phosphine gas.  If a pet eats a phosphide rodenticide and then has a meal shortly thereafter (or has recently eaten) the pet may produce more gastric acid which can, in turn, increase the production of phosphine gas.

My pet won’t eat the poison because I have had it sitting out for X number of months or years and she has never been interested before.

Some pets will leave rodenticides alone for years and then will one day decide the rodenticide looks like a tasty snack.  Don’t assume that your pet would never eat the rodenticide.  Place rodenticides in areas where pets cannot access them.

The brand/active ingredient of the product can be determined by the color of the poison.

Unfortunately, there is no set standard for color-coding rodenticides (though some companies do color code their products).  Many rodenticides are green, regardless of active ingredients, so the poison cannot be determined by bait color alone.  Identifying the product by looking at pictures of rodenticides online is also not an effective way to determine the active ingredient as many of the products look very similar (green blocks, green pellets, yellow squares, etc.) but have very different active ingredients.  The only way to determine the active ingredient is to read the package the product came from or by reading the label left on the bait station by the pest control company so make sure you save the package for any rodenticide you place (even if the package is empty) and any information the pest control company gives you.  While treatment can be provided for pets that have ingested an unknown rodenticide, the pet must be treated for all of the potential active ingredients.  If the active ingredient is known, treatment can be tailored to that specific ingredient and thereby saving your pet from going through extra treatments (and saving you some money).

Vitamin K is the antidote for mouse and rat poisons.

This is partially true.  The anti-coagulant rodenticides (the ones that cause internal bleeding) do have a very effective antidote – prescription-strength vitamin K1.  Vitamin K1 is not effective again the other rodenticides, such as bromethalin and cholecalciferol.