VPT 421: Veterinary Toxicology (2+0)

FACTORS ENHANCING TOXICITY

Factors enhancing toxicity include

• Deficiency of vitamin K due to oral sulphonamides (Prolonged sulphonamide therapy causes decreased synthesis of vitamin K).
• High dietary fat concentration. Fatty acids displace the plasma protein bound anticoagulant increasing the free (active) fraction in the plasma so that more reaches the liver.
• Liver abnormalities or other lesions in tissues that produce blood clotting factor. (Biliary obstruction and liver disease presumably reduces metabolism and excretion of the anticoagulant and reduces clotting factor synthesizing ability).
• Presence of other poisons that cause clotting disorders – haemorrhage, anaemia, haemolysis and methaemoglobinaemia.
• Restraint, motor activity and excitement.
• Presence of drugs (phenylbutazone, oxyphenbutazone, phenytoin, salicylates) that displace the anticoagulant from plasma albumin .
• Administration of ACTH, steroids, or thyroxine which increase the receptor site affinity for the anticoagulant.
• Trauma .
• Renal insufficiency (Uremia also causes decreased binding of the anticoagulant to serum proteins and may slow excretion of the unbound fraction).
• Fever.