Rodent Poisons and Dogs

Common rat and mouse poisons include anticoagulants and hypercalcemic agents. Both can be deadly if your dog ingests them.

Anticoagulant rat and mouse poisons are the most commonly used household poisons. These products account for a large number of accidental poisonings in dogs and cats. Anticoagulants block the synthesis of vitamin K, essential for normal blood clotting. Vitamin K deficiency results in spontaneous bleeding. Observable signs of poisoning do not occur until several days after exposure. The dog may become weak and pale from blood loss, have nose bleeds, vomit blood, have rectal bleeding, develop hematomas and bruises beneath the skin, or have hemorrhages beneath the gums. The dog may be found dead from bleeding into the chest or abdomen. There are two generations of anticoagulants, both in current use. The first generation are cumulative poisons that require multiple feedings over several days to kill the rodent. These poisons contain the anticoagulants warfarin and hydroxycoumadin. Second-generation anticoagulants contain bromadiolone and brodifacoum, poisons that are 50 to 200 times more toxic than warfarin and hydroxycoumadin. These products are more dangerous to pets and are capable of killing rodents after a single feeding. It is even possible for a small dog to be poisoned by eating a dead rodent with residual poison in its stomach. Closely related to the second-generation anticoagulants are the long-acting anticoagulants of the indanedione class (pindone, diphacinone, diphenadione, and chlorphacinone). These products are extremely toxic.

Treatment: Seek immediate veterinary help. If at all possible, bring in the product container so the veterinarian can identify the poison. This is important because treatment depends on whether the poison was a first or second generation anticoagulant. With observed or suspected recent ingestion, induce vomiting.

Treatment of spontaneous bleeding caused by all anticoagulants involves administering fresh whole blood or frozen plasma in amounts determined by the rate and volume of blood loss. Vitamin Kl is a specific antidote. It is given by subcutaneous injection and repeated subcutaneously or orally as necessary until clotting time returns to normal. With first-generation anticoagulants, this often occurs within a week. With long-acting anticoagulants, treatment takes up to a month because of the length of time the poison remains in the dog’s system.

Hypercalcemic agents are poisons that contain vitamin D (cholecalciferol) as their effective agent. Cholecalciferol poisons work by raising the calcium content in blood serum to toxic levels, eventually producing cardiac arrhythmias and death. They are becoming increasingly popular because rodents do not develop resistance to them and, with the rare exception of a puppy or small dog, dogs who eat poisoned rodents will not develop toxicity. In virtually all cases, the dog must eat the poison itself to become ill. In dogs, signs of hypercalcemia appear 18 to 36 hours after ingesting the poison. They include thirst and frequent urination, vomiting, generalized weakness, muscle twitching, seizures, and, finally, death. Among survivors, the effects of an elevated serum calcium may persist for weeks.

Treatment: If you suspect your dog has ingested one of these poisons within the past four hours, induce vomiting and notify your veterinarian. Veterinary treatment involves correcting the fluid and electrolyte imbalances and lowering calcium levels using diuretics, prednisone, oral phosphorus binders, and a low-calcium prescription diet. Calcitonin is a specific antidote, but it is difficult to obtain and has only short-term effects.