07/21/2025
Rat (Rodenticide) Poison Ingested by Pets
Rodent (rat or mouse) poison has been around for a long time. Most people know that when their pet ingests rat poison, they need to take their pet to their veterinarian to be treated. In the past, rodent poison caused a problem with clotting (an anticoagulant) and if left untreated, the animal would bleed to death. The original (first generation) rodenticides were designed to kill the rat/mouse over a period of days. The animal would have to ingest multiple meals before the poison would take effect. Warfarin was initially used to cause the blood to not clot. Over time, it was thought that when a number of dead animals were near the food source (rat poison) that other rodents would avoid the area. In addition, some rodents developed a resistance to warfarin and other similar anticoagulants. Second generation anticoagulants were then developed to avoid the problems encountered with first generation anticoagulants. Second generation rodenticides did not take as much poison to eat to obtain a lethal dose. In addition, second generation rodenticides can take longer for the anticoagulant to work, often 2-4 weeks after ingestion. The active ingredient in the “newer” rodenticides is typically bromadiolone.
Warfarin and bromadiolone block the vitamin K1 cycle that is essential for blood to clot. If you treat your pet with vitamin K1 until all the poison has left the body, you can essentially treat them. Owners do need to be aware that if they have set out second generation rodenticides, that the dead animal (rats, mice, etc.) will still have enough poison in them to cause death to their pet, if eaten. When using rodenticides, be cautious of where they are placed. Pick-up dead rodents/animals immediately and be aware that your pet may gain access to the rodenticide despite your best efforts.
Anticoagulant rodenticides are being phased out due to the concern that they may not humanely kill rodents, since it is a slow death that involves bleeding out. Therefore, owners need to be aware that there are two newer rodenticides that act quite differently and can often result in the death of their pet. The newer rodenticides kill much more quickly and the ability to treat pets has significantly decreased. Signs may be vague or too quick for owners to realize what has happened.
Bromethalin is the active ingredient in one of the newer rodenticides. We are now seeing poisoning due to this product in the area. This poison causes a neurotoxicity that can happen fairly rapidly. Once signs are seen, there is no cure. Bromethalin affects the central nervous system. Depending on the dose; tremors, weakness, seizures, paralysis, incoordination, sensitivity to touch, and/or death may be seen. Any or some of these signs can be seen up to several days after exposure. If the animal is actively found in contact with this rodenticide, immediate action needs to be taken. Contacting your veterinarian and inducing vomiting is the first step. Supportive care can be given as well. Unfortunately, the anticoagulant bromadiolone and the neurotoxin bromethalin are very similar in name, but treated somewhat differently. One way to remember is that bromadiolone (bromo-die-alone) is usually when an animal will crawl off and die. If you can’t remember which poison your pet consumed, try to take a picture of the information from the label or bring the label with you. Your veterinarian should be able to find out which poison to treat for. Cats are more sensitive to bromethalin, so it takes less poison to kill a cat.
A second new rodenticide being introduced has vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) which interfere with the amount of calcium and phosphorous in the blood. When this rodenticide is consumed, the absorption of calcium in food is enhanced and calcium is also pulled from the bones of the animal. The calcium from bone is ionized and able to bind to proteins in the blood. The overall effect is that too much calcium is available and it begins to bind with tissues in the lung, kidney, blood vessels, heart, and the stomach. These organs become mineralized due to the excess calcium and are unable to function normally, which causes further damage to the organs in the body. Hypervitaminosis is the cause of death. Signs may include: lack of appetite, drinking and urinating more, depression, vomiting, constipation, and kidney damage. Once signs of this poison are seen, there is no immediate cure. Whether the poisoned animal survives will depend on what signs are seen and how much organ damage has already been done.
If you suspect or even if you don’t suspect rodenticide poisoning, try to get as much information about the poison as possible. To treat your pet for a suspected poison is much easier than trying to guess if it has happened. With the newer rodenticides there is a very narrow window to treat. Once your pet has absorbed the toxin after several hours, there is very little that can be done. Contact your veterinarian if you have any questions.
For more information on rat poisoning, visit the
24/7 Animal Poison Control Center for both Pet Owners and Veterinarians. If your dog, cat, or other pet is poisoned, call 800-213-6680.
