Details:
Vitamin K1 tablets are used in the treatment of rodenticide poisoning.
Composition
Each tablet contains 25 mg Vitamin K1 (phytomenadione).
Discussion
Over 60 different anticoagulant rodenticide products in South Africa
Majority of anticoagulant rodenticides are Super Warfarins
Second generation agents – Super Warfarins are highly potent
Super Warfarin has a long duration of action – weeks to months after single ingestion
Super Warfarin treatment protocol requires prolonged treatment
Vitamin K1 is a specific antidote for rodenticide poisoning
Vitamin K1 stops bleeding
Vitamin K1 causes aPTT and PT to return to normal/ near normal within 24 hours
Dose rate of Vitamin K1 is dependant on ingestion of first – or second generation rodenticide
Intravenous administration of Vitamin K1is not advisable as it can give a rise of an anaphylactoid reaction
IV administration should only be used where there is a possibility of fatal haemorrhage
Oral Vitamin K1is the preferred route, absorption can be enhanced by concomitant administration of fatty foods
Vitamin K3 injection alone is not advisable, use in combination with Vitamin K1 tablets
Mechanism of Action
Anticoagulant rodenticides interfere with the vitamin K-dependent carboxylation of factors II, VII, IX and X. Depletion of factors II, VII, IX and X inhibits the intrinsic, extrinsic and common clotting pathways. Death is usually associated with the effects of haemorrhage.
The epoxide-reduction enzyme necessary for the recycling of vitamin K is inhibited, resulting in a rapid depletion of body stores of Vitamin K. As vitamin K recycling is reduced or completely halted, a continuous source of vitamin K is essential for production of the above factors and prevention of a coagulopathy.
Clinical Features
These can vary and include:
Lethargy
Petechial and ecchymotic haemorrhages
Respiratory distress
Epistaxis and haemoptysis
Lameness
The animal can occasionally die without external evidence of bleeding.
When intrapulmonary haemorrhage occurs, a secondary bacterial pneumonia can develop.
Treatment
Stabilise and decontaminate the patient
Provide functional clotting factors
Antagonise the effects of anticoagulant on vitamin K1 metabolism
If necessary, compensate for the blood loss that has occurred
Animals presenting with an acute haemorrhagic crisis require administration of whole blood at a rate of 10-20 ml/kg.
The animal should be placed under close observation
Keep the animal warm and quiet.
Unnecessary manipulation and trauma should be avoided.
Dosage
For poisoning with first generation compounds (coumatetralyl, warfarin) the oral dose is 0.5-2 mg of vitamin K1 per kg bodyweight per day administered for 4-6 days.
For poisoning with second generation compounds (brodifacoum, bromadiolone, flocoumafen and difethialone) the oral dose is 2.5-5 mg of vitamin K1 per kg bodyweight per day administered for 2-4 weeks.
