D-CON works by inducing internal bleeding. The active ingredient in d-CON bait traps is a chemical called “brodifacoum”. It prevents the blood from clotting and also damages the capillaries.

When a pest eats the bait in the trap, the poison is absorbed into its blood through the gastrointestinal tract, causing damage to the small blood vessels in the stomach and making it impossible for blood to stop flowing through the wounds. Normally, coagulation would slow and stop flow, but the anticoagulant properties of brodifacoum prevent this natural protective measure from occurring. Eventually, the plague will collapse from loss of blood. The loss of blood continues until the plague dies.

Brodifacoum is not a fast-acting poison and usually takes four to five days to kill after the first ingestion. Because the animal does not cause obvious pain or distress at first, the pest will not develop an aversion to the poison and will continue to feed on toxic baits. Food aversion is a problem with more fast-acting poisons, as the pest will quickly notice something is making it sick and avoid eating a fatal dose of the bait. Bait aversion can spread throughout the pest population. This makes slow-acting poisons more effective at destroying pests in general, even though they take longer to kill.