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==Introduction==
The absolute or relative deficiency of vitamin K can give rise to defective coagulation.
[[Anticoagulant Rodenticide Toxicity|Anticoagulant rodenticide toxiticy]] is one of the most common causes of acquired coagulopathy in small animals. Warfarin itself has a short half-life and a fairly low toxicity in non-rodent species, so unless large or repeated doses are consumed clinical bleeding is rare. However, the second generation anticoagulant rodenticides are far more potent, and it is possible for a domestic animal to acquire secondary poisoning by ingesting a poisoned rodent<sup>1</sup>. Dogs are most commonly effected, but predator species such as cats and owls do occasionally suffer from secondary poisonings.
The [[Normal_Mechanisms_of_Haemostatic_Control#Coagulation_physiology|clotting factors]] - factor VII, factor XI and factors II and X in the extrinsic, intrinsic and common pathways respectively are dependent on Vitamin K when activated by the coagulation cascade.
[[Category:Coagulation Defects]]
==Other Causes of Vitamin K deficiencies==
Malabsorption syndromes and sterilisation of the gastrointestinal tract by prolonged antibiotic usage will also result in the depletion of vitamin K-dependent clotting factors<sup>2</sup>. In herbivores, fungi growing on poorly prepared hay or silage containing sweet vernal grass or sweet clover may break down natural coumarins in the plants to form dicoumarol and cause poisoning.
==Replacement of Vitamin K==
[[Anticoagulant_Rodenticide_Toxicity#Treatment|Vitamin K<sub>1</sub>]] is available as a subcutaneous treatment for cases of [[Anticoagulant Rodenticide Toxicity|rodenticide poisoning]]. Alternatively, whole blood or plasma transfusion provides vitamin K dependent clotting factors, which can control symptoms in severe acute cases.
==References==
#Campbell, A (1999) Common causes of poisoning in small animals. ''In Practice'', '''21(5)''', 244-249.
#Tilley, L P and Smith, W K (2007) '''Blackwell's Five Minute Veterinary Consult: Canine and Feline (Fourth Edition)''', ''Blackwell''.
[[Category:Coagulation Defects]][[Category:Lymphoreticular and Haematopoietic Diseases - Dog]]
[[Category:Cardiology Section]]