NAVLE Veterinary Pharmacology Questions and Answers — Questions and Answers
Question 1: A veterinarian treats a group of feeder calves for bovine respiratory disease (BRD) with enrofloxacin. What is the primary reason for the strict prohibition of extra-label use of this drug in food-producing animals?
- It causes severe and irreversible nephrotoxicity in cattle.
- It causes permanent discoloration of meat products.
- There is a high risk of fatal anaphylactic reactions in human consumers.
- It promotes the development of antimicrobial resistance in human pathogens. (Correct answer)
Correct answer: It promotes the development of antimicrobial resistance in human pathogens.
The FDA prohibits the extra-label use of fluoroquinolones like enrofloxacin in food animals primarily to mitigate the risk of promoting antimicrobial resistance. Bacteria such as Salmonella and Campylobacter can develop resistance, which may then be transferred to human populations through the food chain, compromising the efficacy of this critically important class of antibiotics in human medicine.
Question 2: Which of the following antiparasitic drugs has a narrow margin of safety and is associated with severe neurotoxicity in dog breeds with the ABCB1 (formerly MDR1) gene mutation, such as Collies and Australian Shepherds?
- Ivermectin (Correct answer)
- Fipronil
- Praziquantel
- Selamectin
Correct answer: Ivermectin
Ivermectin, a macrocyclic lactone, can cause severe neurotoxicity in dogs with the ABCB1/MDR1 gene mutation. This mutation results in a defective P-glycoprotein pump, which is responsible for transporting certain drugs out of the central nervous system. Without a functional pump, ivermectin accumulates in the brain, leading to signs like ataxia, tremors, blindness, and coma.
Question 3: A 4-year-old cat requires post-operative analgesia following a routine ovariohysterectomy. Considering feline-specific metabolism and safety profiles, which of the following NSAIDs is licensed and generally considered a safer short-term option for this patient?
- Carprofen
- Acetaminophen
- Robenacoxib (Correct answer)
- Phenylbutazone
Correct answer: Robenacoxib
Robenacoxib is a COX-2 selective NSAID that is specifically licensed for short-term post-operative pain management in cats. Cats have a deficiency in glucuronyl transferase, an enzyme crucial for metabolizing many NSAIDs, making them highly susceptible to toxicity from drugs like acetaminophen (which is extremely toxic) and phenylbutazone. While carprofen is used in dogs, its use in cats is extra-label and more controversial. Robenacoxib's feline-specific approval and COX-2 selectivity provide a better safety margin.
Question 4: Which of the following medications is a potent, broad-spectrum antiemetic that functions by antagonizing neurokinin-1 (NK-1) receptors in the central vomiting center?
- Ondansetron
- Maropitant (Correct answer)
- Metoclopramide
- Famotidine
Correct answer: Maropitant
Maropitant is a neurokinin-1 (NK-1) receptor antagonist. It works by blocking the binding of Substance P, a key neurotransmitter in the emetic pathway, at NK-1 receptors located in the vomiting center and the chemoreceptor trigger zone. This mechanism makes it highly effective against vomiting from both central and peripheral stimuli. Ondansetron is a serotonin (5-HT3) antagonist, metoclopramide is primarily a dopamine (D2) antagonist, and famotidine is an H2-receptor antagonist used to reduce stomach acid.
Question 5: A dog is presented with acute onset of severe muscle tremors, hypersalivation, and miosis after potential exposure to a pesticide. Organophosphate toxicity is suspected. Which combination of drugs is the most appropriate treatment to counteract both the muscarinic and nicotinic effects?
- Atropine and Pralidoxime (2-PAM) (Correct answer)
- Diazepam and Fomepizole
- Vitamin K1 and Methocarbamol
- Naloxone and Epinephrine
Correct answer: Atropine and Pralidoxime (2-PAM)
The standard treatment for organophosphate toxicity involves a combination of Atropine and Pralidoxime (2-PAM). Atropine is a muscarinic antagonist that controls signs like salivation, urination, and bronchoconstriction. Pralidoxime is a cholinesterase reactivator that works to reverse the nicotinic effects, such as muscle tremors and paralysis, by breaking the bond between the organophosphate and the acetylcholinesterase enzyme.
Question 6: A veterinarian administers detomidine to a horse for standing sedation. This drug produces reliable sedation, muscle relaxation, and analgesia by acting as a potent agonist at which of the following receptors?
- Mu-opioid receptor
- NMDA receptor
- GABA receptor
- Alpha-2 adrenergic receptor (Correct answer)
Correct answer: Alpha-2 adrenergic receptor
Detomidine is a potent alpha-2 adrenergic agonist. Stimulation of these receptors in the central and peripheral nervous system inhibits the release of norepinephrine, which results in sedation, analgesia, and muscle relaxation. This class of drugs is commonly used for sedation in large animals.
NAVLE Veterinary Pharmacology Questions and Answers
A veterinarian treats a group of feeder calves for bovine respiratory disease (BRD) with enrofloxacin.
What is the primary reason for the strict prohibition of extra-label use of this drug in food-producing animals?