Downeast Dog News

Rat Poison

By Dr. Judith Herman | Dec 06, 2018

Q. My house is inundated with mice, and they are driving my terrier crazy. I resorted to a poison. Now I am worried Jack will get into it. What signs will I see if he ate some?

A. This is a banner year for rodents. Just driving down the street you see all the rodent road kill. Now with the weather getting cold, the little buggers are coming indoors and driving a lot of dogs batty.

If you are using a poison, care must be taken to keep your dog from ingesting it. There are many rodenticides at your local hardware store or big box store. Read the labels carefully because not all poisons are the same. Here I will go over the more common poisons.

The original rat poisons were anticoagulants. This means that the chemical in the poison keeps the blood from clotting, so the animal that ingests the poison will bleed to death. The active ingredient on the package will say warfarin, chlorophacinone, or diphacinone.

Second generation anticoagulants are called superwarfarins, these include brodifacoum, difethialone bromadiolone, difenacoum. These are so effective only a single dose is needed. These chemicals are slow to be excreted from the body and are stored in the liver. Superwarfarins are so toxic they are only sold to licensed professionals.

So what happens to your dog if he ingests the poison? It takes three to five days before the symptoms appear from the ingested poison. They become lethargic, refuse to eat, and are weak. The symptoms may vary depending on where the bleeding occurs. The dog may cough if the bleeding occurs in the lungs, and he will have pale gums as a sign of internal bleeding. There may be bruising, often seen as purplish spots under the skin. The belly may swell from internal bleeding. You may see bleeding from the nose, gums, and rectum.

The treatment is to give the dog Vitamin K1, which is available by prescription. The treatment is for three to four weeks.

Another class of rat poison contains cholecalciferol. This is a class of vitamin D. Rodents are more susceptible to high doses of vitamin D. A chain of events happen in the rat’s body from the high levels of calcium in the blood caused by the high amount of vitamin D. The rodents develop first kidney failure, then heart abnormalities, high blood pressure, digestive upset, and suppression of their central nervous system. Examples of cholecalciferol containing poisons are Quintox, True Grit, Ortho Rat-B-Gone, Mouse-B-Gone, and Rampage.

Only a small amount of this poison can cause problems in your dog. Call your veterinarian immediately. Within 24 hours, the dog will become weak and lethargic, not eat, vomit, and have an increase in thirst and urination. Two to four days later, he may develop acute kidney failure.

There is no specific treatment for this poisoning. The dog will need extensive supportive care. Aggressive treatment may be necessary for two to four weeks post-ingestion.

Bromethalin rat poison kills by making the brains swell. Examples are Fast Kill, Assault, Vengeance, Tomcat with bromethalin, and Trounce.

A small amount of this can cause problems. If you know your dog ate this, call your veterinarian right away. You will want to induce vomiting. The symptoms are caused by the swelling of the brain. These can include abnormal pupil sizes, wobbly gait, tremors, seizures, hyper-excitability, and death. Symptoms begin 2 to 24 hours after ingestion of the poison. Occasionally, the symptoms develop days later and can only affect the hind legs. There is no specific treatment other than supportive care such as inducing vomiting, gastric lavage, activated charcoal, IV fluids, and careful monitoring. Drugs may be given to decrease the swelling of the brain and control seizures.

The last poison is zinc phosphide. This is usually in poison bait (Moletox) for moles and gophers. This poison releases phosphide gas once it reaches the stomach. It works by blocking the cells from making energy and then the cells die.

In the dog, it only takes a small amount and causes the stomach bloating, vomiting, stomach pain, shock, and liver damage. Guardians are not encouraged to induce vomiting because the gas is a respiratory irritant. If you suspect this type of poison, call your veterinarian right away. Symptoms may develop within a half hour to four hours. There is no antidote for this poison. Treatment management needs to be left up to the veterinarian. The prognosis is guarded.

The bottom line is this: if using rodenticides, make sure the poison is in containers the dog cannot open and placed where he can’t get to it. There are alternatives to these products. Call a professional for help.

If you suspect your dog has ingested poison, call your vet right away and take the box of the poison with you. Every second counts with fast-acting products. Remember the possibility of secondary toxicity if your dog eats a dead rat.


Judith K. Herman DVM, CVH

Animal Wellness Center

Augusta, ME 04330