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Superwarfarin (Long-Acting Anticoagulant Rodenticides) Poisoning: from Pathophysiology to Laboratory-Guided Clinical
Yeow-Kuan Chong1, Tony Wing-Lai Mak1
1Hospital Authority Toxicology Reference Laboratory, Princess Margaret Hospital, Kowloon, Hong Kong, Peoples' Republic of China.
Abstract:
Superwarfarins are long-acting anticoagulant rodenticides developed from warfarin. The mechanism of action is by inhibition of vitamin K epoxide reductase, resulting in the inability of the body to recycle vitamin K. Deficiency of vitamin K thereafter leads to inability for the body to synthesise vitamin K-dependent coagulation factors, factor II, VII, IX, and X, leading to prolonged prothrombin time. Due to the bulky aromatic sidechains, superwarfarins have a much longer half-life when compared to warfarin, and exposure to superwarfarins results in a prolonged period of anticoagulation which can result in clinical bleeding. Diagnosis is straightforward in patients with known history of superwarfarin exposure but has proved difficult for patients who did not report superwarfarin intake. Superwarfarin poisoning should therefore be suspected in all patients with unexplained prolongation of prothrombin time, and can be confirmed by their detection in serum. Treatment for superwarfarin poisoning includes rapid correction of factor deficiencies with either 4-factor prothrombin complex concentrate or fresh frozen plasma in patients with active bleeding, and high dose vitamin K therapy given multiple times per day for a prolonged period of weeks to months.
Insights
Superwarfarins, long-acting anticoagulants, inhibit vitamin K recycling, causing bleeding. Suspect poisoning in unexplained prolonged prothrombin time, treat with vitamin K and factor concentrates.
Area of Science:
- Toxicology
- Pharmacology
- Hematology
Background:
- Superwarfarins are extended-acting anticoagulant rodenticides derived from warfarin.
- They function by inhibiting vitamin K epoxide reductase, disrupting vitamin K recycling.
- This leads to a deficiency in vitamin K-dependent clotting factors (II, VII, IX, X), prolonging prothrombin time.
Purpose of the Study:
- To elucidate the mechanism, diagnosis, and treatment of superwarfarin poisoning.
- To highlight the diagnostic challenges in cases without reported exposure.
- To emphasize the prolonged nature of superwarfarin anticoagulation and its clinical implications.
Main Methods:
- Review of superwarfarin pharmacology and toxicology.
- Discussion of diagnostic approaches, including prothrombin time monitoring and serum detection.
- Outline of treatment strategies involving vitamin K and coagulation factor replacement.
Main Results:
- Superwarfarins possess longer half-lives than warfarin due to their structure.
- Clinical bleeding can occur due to prolonged anticoagulation.
- Diagnosis can be challenging without a history of exposure, necessitating suspicion in unexplained coagulopathy.
Conclusions:
- Superwarfarin poisoning requires high suspicion in patients with unexplained prolonged prothrombin time.
- Confirmation is achieved through serum detection of superwarfarins.
- Treatment involves aggressive vitamin K therapy and factor replacement for bleeding patients, often for extended durations.
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