SOURCES

The anticoagulant rodenticides were developed following investigations of moldy sweet clover poisoning in cattle. In this well-known syndrome, the naturally occurring coumarin in the clover is converted by fungi to dicumarol, the toxic agent.¹ Warfarin was initially synthesized during these investigations of moldy sweet clover poisoning. It was subsequently marketed as a rodenticide. Rodent species, however, have since developed resistance to it,² so compounds effective against warfarin-resistant rodents have been developed. These second-generation anticoagulant rodenticides are now more common than warfarin for rodenticide use. They include brodifacoum, bromadiolone, chlorophacinone, coumafuryl, difenacoum, difethialone, diphenadione (synonym: diphacinone), pindone, and valone. Coumachlor, coumatetralyl and flocoumafen have not been marketed in the United States, and valone distribution in the United States was discontinued in 1993. The greater efficacy of these products against rodents is associated with a greater potential toxicity to nontarget species.

Domestic animals are sometimes inadvertently, and occasionally maliciously, exposed to anticoagulant rodenticide baits. In fact anticoagulant rodenticides are second only to cholinesterase inhibitors as a cause of death in dogs and cats. Dogs are more commonly poisoned than cats. Some reports have indicated no seasonal predilection; however, in the Pacific Northwest, the majority of confirmed anticoagulant cases occur in the late fall and early spring when rodent activity is high. This apparent discrepancy may be associated with the source of the samples received—such as urban versus rural, and national versus regional. Nevertheless, brodifacoum is the active ingredient most commonly identified in cases of anticoagulant rodenticide–induced coagulopathies diagnosed in either the Washington State University (WSU) Veterinary Teaching Hospital or the Minnesota Veterinary Diagnostic Laboratory. Diphenadione (diphacinone), bromadiolone, and chlorophacinone come in as distant second, third, and fourths, and warfarin accounts for less than 10% of diagnoses. A partial list of the many anticoagulant rodenticide products on the market is present in Table 30-1. Anticoagulant rodenticide products come in grain-based pellets, minipellets, wax-paraffin blocks, meal baits, dry concentrates, water bait, tracking powder, ground spray, whole and broken grains, nylon pouches, coated talc, and dust. Concentrations of the active ingredient vary from 0.05% to 0.25% between products, but is consistent for a given product. So toxic dosages are reported as both mg/kg body weight (BW) and as ounces of bait/kg BW (Table 30-2).

Table 30-1 Trade Names and Names of the Active Ingredient for Some Anticoagulant Rodenticide Products^*

* Some products may be discontinued and unavailable for purchase.

Table 30-2 Toxicity and Therapy for Anticoagulant Rodenticides

Stay updated, free articles. Join our Telegram channel

Join