Coumadin (a blood thinner)...is also used in Rat Poison..
Oh the Irony
Warfarin, also known by the brand names Coumadin, was first used as a rat poison or rodenticide because it was considered to be too potent to be safely used in humans, but after a blood test was developed to measure and adjust its blood-thinning effects, warfarin has become the most widely used oral anticoagulant in the United States.