Veterinary Pharmacology and Toxicology
Veterinary Pharmacology and Toxicology
This domain tests drug action, pharmacokinetics, dose calculation, withdrawal periods, antidotes, and poisoning by chemicals, plants, and minerals.
Core rules
- Pharmacokinetics: absorption, distribution, metabolism, excretion. Bioavailability, half-life, and volume of distribution guide dosing.
- Drug classes include antimicrobials, anthelmintics, anti-inflammatory drugs, anaesthetics, and autonomic drugs.
- Withdrawal periods protect food safety; milk and meat residues are regulated.
- Toxicology: dose makes the poison; know common toxicants: organophosphates, nitrate, lead, urea, mycotoxins, and plants.
- Antidotes: atropine for organophosphate muscarinic signs; methylene blue for nitrite; calcium for hypocalcaemia.
Worked example
A cow has salivation, miosis, diarrhoea, and muscle twitching after spraying an insecticide. Reasoning: muscarinic signs plus nicotinic twitching suggest organophosphate poisoning from acetylcholinesterase inhibition. Give atropine to block muscarinic effects; pralidoxime can reactivate enzyme if given early. Remove contaminated material and observe milk withdrawal.
Traps
- Expecting atropine to reverse nicotinic muscle twitching.
- Confusing nitrate poisoning with cyanide; both cause hypoxia but treatment differs.
- Ignoring species sensitivity: goats and horses differ in drug handling.
- Forgetting withdrawal periods after emergency treatment.
Exam focus
Calculate doses by body weight and check units. Match toxidrome to antidote and residue risk.