Superwarfarin poisoning is considered a significant public health problem in the US. In 2004, there were 16 054 cases of poisoning; most were accidental ingestions of rat bait by children but 4576 patients required hospital treatment, 23 patients had major adverse outcomes and 1 patient died. Similar information is unavailable for the UK. The National Poisons Information Service is presently auditing cases.
The case of a farmer who presented with haematuria, 9 days after spilling a rodenticide containing a superwarfarin over himself is reported here. He was physically well except for mild abdominal tenderness. He had grossly deranged clotting studies (prothrombin time (PT) >200 s, activated partial thromboplastin time (APTT) 56 s) that were rapidly corrected with fresh frozen plasma and vitamin K. He was sent home after 5 days without follow up. Unfortunately, he presented again 2 days later, again with haematuria and an international normalised ratio (INR) >10. He required inpatient treatment with high-dose vitamin K for 1 week. Upon discharge, he required daily vitamin K and INR monitoring for a further month. The original inpatient team had not identified the specific poison (chlorophacinone). They were unaware that superwarfarins are more potent and longer acting than warfarin, with toxic effects for weeks or even months, and that large doses of vitamin K are often required.
- APTT, activated partial thromboplastin time
- INR, international normalized ratio
- PT, prothrombin time
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