May 30, 2011 – Anticoagulant Truths


I recently researched toxicity of rodenticides for a customer and came upon a paper from a large veterinarian school that claims second generation anticoagulants are extremely toxic to pets, and standard known antidotes (vitamin K1) are not as effective as we are led to believe. For me this muddies the water as to which product to use in bait stations. Please provide some clarity on this topic, as the pending new rodent regulations may have us all doing more rodent work for consumers.


I have always been nervous about the word "antidote" when referring to Vitamin K for anticoagulant poisoning. In my mind, and perhaps in the minds of many other people, the word antidote summons up the vision of a one-time injection of something that reverses the effect of a toxin, and this is absolutely not the case with anticoagulant rodenticides. To me a much better word (instead of antidote) would be "treatment", because it may be necessary to continue to treat that animal for as long as it takes for the animal's system to metabolize and excrete the active ingredient, and this (according to some manufacturers) could be as long as 4 months. Dr. Robert Corrigan states in his book on Rodent Control that this misconception may exist, and that a single injection often is not sufficient. It depends on the species of non-targeted animal (cat, dog, hawk, etc.), the specific active ingredient involved, how much was eaten, the age, health, and weight of the animal. It may be that the veterinarian is going to need multiple doses of the treatment over a long period of time, possible blood transfusions, and possible surgical needs. The first generation anticoagulants (warfarin, diphacinone) are metabolized and excreted from a dog's body much more quickly than are the second generation anticoagulants (brodifacoum, bromadiolone, difethialone). The reason these secondary actives are called "single feeding" is because their toxicity is so much higher than the first generation products, and for this reason they require a MUCH smaller amount of bait to be eaten to cause their death. This definitely could translate to their being a much higher hazard to pets and wildlife if used improperly, and also leads to that greater concern of non-target animal consumption and secondary poisoning. I am not certain that there is any change in how effective Vitamin K is for treating anticoagulant poisoning, other than the need to continue the treatments for a much longer time than may be necessary with first generation active ingredients. This concern with the second generation products is likely a major part of the decision by EPA to completely eliminate the sale of second generation actives to the unlicensed and untrained general public. After June 4 this year the new laws go into effect, and once existing inventories are depleted you will find the important new labeling on rodent baits. So, without reading the exact wording of this paper you read it sounds to be fairly spot-on correct. However, there has been recent animal-rights activity in the California media that slams rodent baits, and claims that rodenticides are the current Environmental Armageddon, and suggests that wildlife is dropping dead in large numbers due to secondary poisoning. I think this is likely a terrible exaggeration on their part in their effort to be noticed, but the fact is that we need to be very, very careful of how we use rodent poisons, and that secondary poisoning could occur.

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