Vitamin K1 is the antidote to anticoagulant rodenticide toxicosis. It works by restoring vitamin K body stores and allowing synthesis of clotting factors required for the clotting cascade. It is given prophylactically and in the management of acute coagulopathy.
Many sources state that vitamin K1 takes time, sometimes hours, to work and so in an animal with bleeding rapid restoration of clotting factors requires a blood transfusion. There is however little information to support this delay. A recent case series describes four dogs with anticoagulant rodenticide-induced coagulopathy managed with intravenous vitamin K1. Testing at 1 hour showed that the prothrombin time (PT) has normalised in all cases. None of the dogs required blood products and all recovered.
It is worth noting that different intravenous vitamin K1 products are available and some contain excipients that are commonly associated with anaphylactoid reactions. This is not the case with the product licensed for veterinary use in the UK. The cases described above occurred in Australia using a different product and two of the four dogs had adverse events associated with the use of vitamin K1 products containing these excipients.
It appears that intravenous vitamin K1 may be sufficient to correct coagulopathy in some cases of anticoagulant rodenticide toxicosis in dogs. Blood products, however, will be needed in dogs with severe haemorrhage and blood loss or hypovolaemia.