Veterinary Pharmacology and Toxicology
Veterinary pharmacology and toxicology tests drug classes, routes, doses, withdrawal periods and poison management. The exam often uses a field poisoning scenario or a drug-choice question where one detail changes the answer.
Core rules
- Antibiotics: beta-lactams (penicillin) target cell wall; tetracyclines and macrolides inhibit protein synthesis; fluoroquinolones inhibit DNA gyrase. Use culture and sensitivity where possible.
- Anti-inflammatory drugs: NSAIDs inhibit cyclo-oxygenase; corticosteroids are not interchangeable with NSAIDs and can worsen infection or ulcers.
- Withdrawal periods protect milk and meat residues; follow label and species. Never use prohibited substances in food animals.
- Toxicology: organophosphate poisoning causes salivation, miosis and muscle twitching-treat with atropine and pralidoxime; nitrate/nitrite poisoning causes chocolate-brown blood-methylene blue; urea poisoning causes bloat and tetany-acidify with vinegar and cold water; warfarin poisoning-vitamin K1.
- Dose by body weight; check concentration, not just volume.
Worked example
A buffalo accidentally eats urea fertiliser and shows bloat and tremors. Reasoning: urea is rapidly hydrolysed to ammonia in the rumen; ammonia raises pH, causes CNS signs and rumen stasis. Give cold water and vinegar to acidify rumen contents, relieve bloat, and call for veterinary support. Atropine would be wrong because the signs are not cholinergic; methylene blue would be wrong because blood is not methaemoglobinaemic.
Traps
Do not confuse oxytetracycline with oxytocin. Do not use atropine for nitrate poisoning. Do not ignore species differences-some drugs are toxic to dogs, cats or poultry. Do not state a withdrawal period without checking the product label.