A pesticide that is specifically designed to control rodents is called a rodenticide. The most commonly used rodenticides in the U.S. contain bromadiolone, brodifacoum, difethialone, or diphacinone. While there are many different variations of rodenticides, these particular ones are similar in that they are all anticoagulants, which are a type of blood thinner that prevents blood from clotting. In mammals and birds, the liver produces a particular enzyme that allows the body to recycle vitamin K, which is the main component needed to prevent humans and other animals from bleeding out. The process works the same for injuries both inside and outside the body. Anticoagulants work by targeting and disabling the enzyme that allows blood to clot.