VTNE Veterinary Pharmacology Questions and Answers — Questions and Answers
Question 1: A veterinarian prescribes phenobarbital for a 5-year-old dog diagnosed with idiopathic epilepsy. What is the primary mechanism of action for this drug?
- Blocking voltage-gated sodium channels
- Enhancing the effect of the inhibitory neurotransmitter GABA (Correct answer)
- Antagonizing glutamate receptors
- Inhibiting the reuptake of serotonin and norepinephrine
Correct answer: Enhancing the effect of the inhibitory neurotransmitter GABA
Phenobarbital, a barbiturate anticonvulsant, primarily works by potentiating the effect of gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the central nervous system. It binds to GABA-A receptors, which increases the duration of chloride channel opening, leading to hyperpolarization of the cell membrane and reduced neuronal excitability.
Question 2: A 12-kg dog is prescribed carprofen for osteoarthritis at a dose of 2.2 mg/kg BID. The clinic stocks 50 mg scored tablets. How many tablets should be dispensed for a 10-day supply?
- 5 tablets
- 10 tablets (Correct answer)
- 20 tablets
- 15 tablets
Correct answer: 10 tablets
First, calculate the single dose in mg: 12 kg * 2.2 mg/kg = 26.4 mg. Since the tablets are 50 mg and scored, the dog will receive a half tablet (25 mg) per dose. The dosing is BID (twice a day), so the dog needs 2 doses per day. For a 10-day supply, the total number of doses is 2 doses/day * 10 days = 20 doses. Since each dose is a half tablet, the total number of tablets is 20 doses * 0.5 tablets/dose = 10 tablets.
Question 3: Which of the following is a common, and potentially serious, class-wide side effect of non-steroidal anti-inflammatory drugs (NSAIDs) in dogs?
- Polyuria and polydipsia
- Gastrointestinal ulceration (Correct answer)
- Iatrogenic hyperadrenocorticism
- Alopecia
Correct answer: Gastrointestinal ulceration
NSAIDs work by inhibiting cyclooxygenase (COX) enzymes, which reduces the production of prostaglandins. While this decreases inflammation and pain, it also reduces the production of prostaglandins that protect the stomach and intestinal lining. This can lead to gastrointestinal irritation, ulceration, and even perforation, which is a major risk associated with NSAID use.
Question 4: A Collie presents with severe neurological signs, including ataxia and seizures, after receiving a high dose of ivermectin for mange treatment. This adverse reaction is most likely due to a mutation in which gene?
- CYP2D15
- NK-1
- MDR1 (ABCB1) (Correct answer)
- COX-2
Correct answer: MDR1 (ABCB1)
Certain breeds, particularly Collies and related breeds, can have a mutation in the Multidrug Resistance Gene (MDR1), also known as the ABCB1 gene. This gene codes for P-glycoprotein, a transport pump that is part of the blood-brain barrier and actively removes certain drugs, like ivermectin, from the brain. A defective gene leads to the accumulation of the drug in the central nervous system, causing neurotoxicity.
Question 5: Maropitant (Cerenia®) is a widely used antiemetic in veterinary medicine. It provides broad-spectrum anti-vomiting effects by acting as a:
- Dopamine D2 receptor antagonist
- Serotonin 5-HT3 receptor antagonist
- Histamine H1 receptor antagonist
- Neurokinin-1 (NK-1) receptor antagonist (Correct answer)
Correct answer: Neurokinin-1 (NK-1) receptor antagonist
Maropitant is a potent and selective antagonist of the Neurokinin-1 (NK-1) receptor. It works by blocking the binding of Substance P, a key neurotransmitter involved in the vomiting reflex, at the NK-1 receptors in the emetic center of the brain. This mechanism makes it effective against vomiting triggered by both central and peripheral stimuli.
Question 6: A veterinarian prescribes Clomicalm® (clomipramine hydrochloride) for a dog with separation anxiety. Which of the following is a potential side effect that the owner should be counseled about?
- Increased aggression
- Hyperactivity
- Lethargy or sedation (Correct answer)
- Polyphagia
Correct answer: Lethargy or sedation
Clomipramine is a tricyclic antidepressant. One of the most common side effects, especially during the initial phase of treatment, is lethargy or sedation. While other side effects like vomiting or changes in appetite can occur, sedation is frequently observed as the animal adjusts to the medication. Increased aggression is not a typical side effect and the drug is not recommended for treating aggression.
VTNE Veterinary Pharmacology Questions and Answers
A veterinarian prescribes phenobarbital for a 5-year-old dog diagnosed with idiopathic epilepsy.
What is the primary mechanism of action for this drug?