Toxicology

Learning Outcomes Define poison, toxin, antidote Discuss how animals obtain access to poisons Review the common categories of poisons and major clinical signs Explain the use and preparations required for standard emergency therapy Explain the products and equipment used in an emergency poisons kit Explain the recommendations for inducing vomiting Explain the information required from the owner at the time of contact Be able to give advice to owner on convalescent patients

definitions Poison: substance causing injury, illness or death Toxin: poisonous substance, usually a protein, produced by living cells and capable of causing tissue damage. Usually induces an antibody/antitoxin formation. Antidote: remedy to counteract the effects of poison  

“The dose makes the poison” To cause intoxication a substance must be absorbed and delivered to the site of action at a concentration high enough to elicit a physiological response. poisons are susceptible to the same processes of absorption, distribution, metabolism and excretion that drugs are.

Absorption: prevention of absorption is an essential goal of tx of poisoning gastric decontamination (emesis, activated charcoal, gastric lavage, whole bowel irrigation) dermal decontamination (washing skin)

metabolism it is preferable to make toxins water soluble which aids elimination. Note that metabolism of a toxin does not always alter its toxicity, it may be more less or the same degree of toxicity.

Excretion Distribution consider urine, faeces, bile, air, milk, saliva, sweat. Note public health significance of milk. Distribution Distribution to the site of action is affected by organ perfusion, lipid solubility, protein binding, tissue affinity, special barriers e.g. blood/brain barrier.

Animal access to poisons Two most commonly involved species are dogs (36%) and cattle (24%) Most common types of poisonings Pesticides 45% (of which rodenticides 42%) Pollutants 20% Veterinary drugs 19% Plants 14%

Therapeutics(Tx the patient not the poison) TARA SAIES FuE Telephone advice TA Reduce absorption RA Specific antidotes SA Increase elimination IE Supportive S Future exposure FuE

Role play telephone advice Discuss the role of the veterinary nurse in the first aid of poisoning patient. Then in threes, one as a client, one as vet nurse on the phone, one observer. Choose a poison from the list at the back of the notes(other than slug bait and rat bait), prepare what you will say for a few minutes then do your role play, observer to feedback on what went well, points for improvement etc.   Discuss your response to an owner ringing with concerns about a pet suffering from a possible deliberate poisoning by the neighbour who has complained about the dog barking. Why is it particularly important to take care with what you say and agree with the owner about in this case?

Decontamination process of the conscious animal Why is there a difference in treatment of the animal that has swallowed a known poison less than 4hrs ago from one that swallowed it longer than 4 hrs ago? When would home treatment using emetics be recommended? What are the emetics that can be used for emergency home treatment if they are available? What are the emetics that are usually used at the clinic for dogs? For cats? If emetics cannot be used what options has the clinic got for reducing absorption? What are 4 contraindications for using emetics and why are they contraindicated? What should be given to an animal that has ingested a corrosive poison? After 4 hrs solid material will have passed through the stomach and vomiting will not remove it once it is distal to the pyloric sphincter.(fluids may pass through more quickly) When the owner cant reach the clinic within the 4 hrs Hydrogen peroxide 3%, Sodium Carbonate, Dry mustard, Zinc sulphate Dogs – Apomorphine, Cats – xylazine Activated charcoal, laxative, possibly gastric lavage corrosives, volatile hydrocarbons, unconscious, rabbit, rodent, horse, ruminant, convulsive agents/convulsions, coma. Corrosives and hydrocarbons damage the GIT on the way down so don’t want to do further damage on the way up, unconscious animals have no protective airway reflexes and there is risk of aspiration pnuemonia, rabbit horse etc cant vomit dilute with milk

Specific antidote, increase elimination and supportive therapy

Prevent future exposure Prepare a poster that you could put in the prep room to remind you what to do in poison cases.