Accidental poisoning with a superwarfarin compound (brodifacoum) in a child

The "superwarfarin" compounds are 4-hydroxy derivatives of coumarin that have increased activity and a longer duration of action than the parent compound. The superwarfarins are used widely in the United States as rodenticides and are effective against warfarin-resistant strains of rats. A chronic accidental ingestion of one of these products, brodifacoum, by a 7-year-old child who had bleeding and laboratory evidence suggestive of a vitamin K-related coagulopathy is reported. The bleeding manifestations were severe and prolonged, requiring 13 months for normalization of coagulation times. With a negative history of ingestion and despite clinical suspicion, documentation of superwarfarin poisoning was hampered by the lack of readily available assays for these compounds, even from the manufacturers. Brodifacoum was also identified in rat feces from the family home. This finding raises the concern of poisoning not only from ingestion of brodifacoum particles themselves, but also from a fecal-oral route. A review of the literature is presented and the implications of this case for the practicing physician are discussed.