https://orcid.org/0009-0008-4898-7760
Dear Editor,
Bromadiolone, a second-generation anticoagulant rodenticide, has a long half-life [Citation1,Citation2]. It is a vitamin K antagonist, inhibiting the synthesis of factors II, VII, IX, X, proteins C, S, and Z [Citation3]. Poisoning causes protracted coagulopathy [Citation3,Citation4], which is reversible with phytomenadione (vitamin K1) [Citation3]. There are limited toxicokinetic data on bromadiolone poisoning. We report a life-threatening case of suspected repeated homicidal bromadiolone poisoning, complicated by concealed poisoning and complications to medical treatment.
A previously well 24-year-old university student, overseas on language exchange, became unwell. Over several weeks, he had multiple emergency department presentations for symptoms, including dizziness, headache, and abdominal pain. He was diagnosed with acute pyelonephritis when he was noted to have haematuria with pyuria. Worsening symptoms and further spontaneous bleeding (epistaxis, ecchymosis, haematuria) prompted a return to the emergency department. Upon first testing, his international normalized ratio was >7.86, and the prothrombin time was >90.0 s. As warfarin-like poisoning was suspected, his coagulopathy was treated with high-dose intravenous phytomenadione and fresh frozen plasma. He developed a rash, fever, pulmonary oedema, and circulatory shock, features which were considered to be either anaphylactoid reactions to phytomenadione or due to fresh frozen plasma-related acute lung injury or sepsis. Over the subsequent 1–2 weeks, blood product transfusion and parenteral phytomenadione were reintroduced multiple times, with variable reactions. His international normalized ratio then fluctuated between 2.3 and 7.8.
He was medically retrieved to Australia for ongoing management in a clinical toxicology unit. Phytomenadione 50 mg orally twice daily maintained his international normalized ratio <1.4. Poisoning with an anticoagulant rodenticide was confirmed with a serum bromadiolone concentration of 510 µg/L. A qualitative extended urine drug screen tested positive for amlodipine, which was never administered therapeutically. The bromadiolone concentration rapidly decreased from 510 to 150 µg/L over a four-day period (). Phytomenadione was discontinued once his bromadiolone concentration was <10 µg/L, forty-one days after returning to Australia. The source of the poisoning was eventually revealed to be a friend he had moved in with when he had become unwell, in what appeared to be a Munchausen’s syndrome by proxy scenario. After the suspicion of poisoning arose, a blended juice prepared for the patient was qualitatively analyzed, testing positive for bromadiolone.
Figure 1. Bromadiolone concentration.
Bromadiolone elimination kinetics appear to have a two-compartment model, with a period of rapid clearance followed by a delayed second phase [Citation3]. The bromadiolone apparent half-life was 2.2 days for the first phase and 5.9 days for the terminal phase. This is notably shorter than that reported in a previous case of 3.5 and 24 days, respectively [Citation3]. This patient’s clinical course was complicated by possible severe anaphylactoid reaction to phytomenadione intravenously. While rare, this is well reported, with an incidence of 3 per 10,000 doses [Citation5]. Oral phytomenadione is associated with fewer anaphylactoid reactions and is safe to use in patients who suffer reactions to the intravenous preparation [Citation5].
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References
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