Flocoumafen is a fluorinated, second-generation anticoagulant of the 4-hydroxycoumarin vitamin K antagonist type. It is a second generation (i.e., high potency) chemical in this class, used commercially as a rodenticide. It has a very high toxicity and is restricted to indoor use and sewers (in the UK). This restriction is mainly due to the increased risk to non-target species, especially due to its tendency to bio-accumulate in exposed organisms. Studies have shown that rodents resistant to first-generation anticoagulants can be adequately controlled with flocoumafen. It was synthesized in 1984 by Shell International Chemical.
In most rodents, the is 1 mg/kg, but it can vary between species: from 0.12 mg/kg in the common vole (Microtus arvalis) to more than 10 mg/kg in the Cairo spiny mouse (Acomys cahirinus). For dogs the LD<sub>50</sub> is 0.075-0.25 mg/kg.
The antidote to flocoumafen is vitamin K<sub>1</sub>, which must be administered over a period of several weeks or even months.