Brodifacoum:Mechanism of Toxicity

Brodifacoum is a 4-hydroxycoumarin anticoagulant that acts as a vitamin K antagonist. It was registered as a pesticide in 1979 in the United States although in 2008 it was made a restricted use pesticide by the Environmental Protection Agency. This means it can only be used by certified pesticide applicators; however, the makers of D-Con which contains 0.005% brodifacoum by weight have challenged this and brodifacoum is currently available in D-Con and in various other pesticide products for the eradication of mice and rats although it is also used on larger mammals such as possums. Brodifacoum currently remains available to the general public.

Use

Brodifacoum is used as a rodenticide (commonly 0.005% by weight).

Mechanism of Toxicity 

Brodifacoum has a very low solubility in water and typically enters water through erosion where it is then found in the sediment. Brodifacoum concentrations are typically not measurable in water systems.
Products that contain brodifacoum as pesticide can remain toxic for a long period of time in the environment. The rate of decay of brodifacoum depends upon the amount of rainfall. As the product that contains brodifacoum degrades over time, the brodifacoum is absorbed into the soil. Soil bacteria degrade brodifacoum over weeks to months although soil type, temperature, and the presence of microorganisms that will degrade brodifacoum all influence the time it takes to degrade.

Environmental Fate

Brodifacoum, like other hydroxycoumarins, interferes with the production of vitamin K–dependent coagulation factors. Vitamin K is a cofactor for the carboxylation of specific glutamic acid groups in coagulation factors II (prothrombin), VII, IX, and X. During this step, vitamin K is oxidized to vitamin K 2,3-epoxide. The regeneration of vitamin K by vitamin K 2,3-epoxide reductase is prevented by brodifacoum. As a result, dysfunctional decarboxy-coagulation factors are produced and coagulation is impaired. Brodifacoum is over 100 times more potent than warfarin on a molar basis in rats.