RAT POISON (ANTICOAGULANT RODENTICIDES)
ANTICOAGULANT RODENTICIDES AND YOUR PET
Typical active ingredients are: brodificoum, diphacinone, warfarin, bromadiolone, and others. Most of these products include green dyes for a characteristic appearance; however, dogs and cats have poor color vision and to them these pellets may look like kibbled pet food.
Anticoagulant rodenticides do not produce signs of poisoning
Anticoagulant rodenticides cause internal bleeding.
A poisoning victim will show weakness and pallor
Most of the time external bleeding is not obvious and one only notices the pet is weak and/or cold. If one looks at the gums, they are pale. Sometimes bloody urine or stool is evident or nose bleeds may be seen. Signs of bleeding in more than one body location are a good hint that there is a problem with blood coagulation and appropriate testing and treatment can be started.
HOW DOES RAT POISON WORK?
blood clotting in action
To understand what these poisons do, it is necessary to have some understanding of how blood clots. A blood vessel is sort of like a pipe carrying rapidly flowing blood along its path. The “pipe” is lined by smooth flat cells called “endothelial cells” which facilitate the smooth flow of the blood. If the pipe breaks, the structure of the pipe below the lining is exposed to the flowing blood inside. From there the sequence of events is as follows:
ABOUT THOSE SERINE PROTEASES:
Clotting factors are identified by number and the serine proteases (also called “K-dependent factors for reasons which are about to become clear) are factors II, VII, IX, and X. These factors are produced in an inactive state by the liver and go happily circulating through the bloodstream awaiting activation. When a vessel tears and it becomes necessary to form a clot, these factors are activated in a process that requires Vitamin K (a fat soluble vitamin not as famous as its fat-soluble cousins Vitamins A and E). As the clotting factors are activated, Vitamin K is inactivated but later recycled by another set of enzymes to be ready to participate in clotting factor activation again later.
As long as there is plenty of Vitamin K,
The anticoagulant rodenticides abolish Vitamin K recycling.
This means that as soon as one’s active Vitamin K reserves are depleted,
In cases of poisoning one would expect symptoms to be nearly immediate but in the case of anticoagulant rodenticide poisoning, it takes several days to deplete Vitamin K. After that, even the smallest of jostles and traumas can lead to life-threatening bleeds.
Another test called the “PIVKA” (“Proteins Induced by Vitamin K Antagonism”) test is more specific. The PIVKA test detects inactive serine proteases. If an unusually high amount of inactive serine proteases are circulating that would indicate something is wrong with Vitamin K recycling.
If the patient has only just ingested the poison, he or she may be made to vomit it up. Cathartics and absorbents can be used to prevent the poison from entering the patient’s system. Still, it is prudent to use the antidote anyway. Certainly, if there is evidence that the patient is bleeding, the antidote obviously is required.
The antidote is simply Vitamin K.
Vitamin K is generally started as an injection and when the patient is stable. Tablets are prescribed. The human formulation, available as a prescription drug at most drug stores, is a 5mg tablet. The veterinary strength is a 25mg tablet. Blood transfusions may be needed to stabilize a patient who has suffered significant blood loss.
Blood for Transfusion
(original graphic by marvistavet.com)
There are different classes of anticoagulant rodenticides and they remain in the body for several weeks. It is hard to know when to discontinue therapy, especially if the particular rodenticide is not known. After a couple of weeks of therapy, medication is discontinued. Forty-eight hours later a PT test is run. If there is still rodenticide in the patient’s system, the PT will abnormal but the patient will not yet have started to bleed. The results of the PT test will tell the veterinarian whether or not another couple of weeks of Vitamin K are needed.
It is very important to return for the recheck PT test on schedule.
There is no point to doing the PT test while the patient is still taking Vitamin K. The test must be done 48 hours after discontinuing the medication.
When the PT test has returned to normal it is safe to discontinue therapy.
VITAMIN K1 VS. VITAMIN K2 VS. VITAMIN K3
There are three forms of vitamin D but only Vitamin K1 is used therapeutically. Vitamin K1 is a natural form of Vitamin K which is found in plants and absorbed nutritionally. Its more technical name is "phylloquinone." Vitamin K2 ("menaquinone") is also natural and is produced by one's intestinal bacteria but apparently not in amounts adequate for rescue from the anticoagulant rodenticides. Vitamin K3 ("menadione") is a synthetic version which may be injected or taken orally. You may even see it available as a vitamin supplement tablet.
Within the body Vitamin K1 and Vitamin K3 are converted to Vitamin K2. Vitamin K3 might seem like an inexpensive way to treat a pet with rat poisoning but unfortunately, K3 is sometimes toxic and can actually lead to red blood cell destruction. Inexpensive Vitamin K3 pills on the drugstore shelf for over-the-counter sale are not acceptable antidotes. Vitamin K1 is used because it is absorbed early in the GI tract and concentrates directly in the liver which is where the serine proteases are activated. It is only Vitamin K1 which should be considered to be the antidote for anticoagulant rodenticide poisoning.
While anticoagulant rodenticide poisoning is a life-threatening event, at least there is an antidote readily available. Other rodenticides are not as readily reversed. Other rodenticides on the market include:
Strychnine (gopher bait)
Zinc Phosphide (gopher bait)
Page last updated 11/5/2016