VPT 421: Veterinary Toxicology (2+0)

TREATMENT

• Prevent further absorption
• Maintain airway
• Maintain blood pressure and airway
• Control convulsions
• Administer atropine – Atropine will block the muscarinic symptoms. In high doses, it can control central effects. But, it does not reverse peripheral muscular paralysis, which is mediated by nicotinic actions. The dose required is 0.2 – 0.5 mg/kg, one-fourth given intravenously and the rest intramuscularly or subcutaneously. The dose must be repeated at 3 – 6 hour intervals for a day or more. Adequate atropinisation exists when the pupils are dilated, salivation ceases and the animal appears to be recovering.
• Administer cholinesterase reactivators – After atropinisation, before aging, oximes should be administered.
  • Cholinesterase reactivators can be used to counter the nicotinic receptor activation. Reactivators include diacetylmonoxime (DAM), pralidoxime (2 PAM), toxagonine etc. 2PAM chloride is the drug of choice because of the solubility and stability in water and few side effects. Oximes work best in the presence of atropine and hence should be given after atropinisation. 2 PAM chloride is administered at the rate of 20 – 50 mg/kg of 10% solution i/m or slow i/v in small animals and 25 – 50 mg/kg of 20% solution i/v in a 6 minute duration. If symptoms of toxicosis reappear, the dose can be repeated.
• Oximes work by two mechanisms
  • They react directly with the organophosphate and form a relatively non toxic complex. This can be excreted in urine. So the organophosphate is removed from the cholinesterase and cholinesterase can metabolize acetylcholine.
  • If aging has not occurred in phosphorylated esters, the oximes are capable of breaking the bond between the esteratic site of acetylcholinesterase and the phosphoryl group of the pesticide. In this oxime gets phsophorylated and acetylcholinesterase is liberated.
• Oxygen therapy if cyanosis and dyspnoea are prominent.
• Washing the animal with plenty of water and detergent.
• Administration of mineral oil.
• Keeping the animal quiet and comfortable.
• Oximes are not effective in carbamate poisoning. The anionic site is not free for the oximes to be attached to, in the case of carbamate poisoning. So they are ineffective. Oximes themselves have weak anticholinesterase activity and hence, they are contraindicated in carbamate poisoning. Administering oximes in carbamate poisoning will aggravate the condition.