NAVLE Veterinary Pharmacology 5 — Questions and Answers
Question 1: Which drug is the antidote for acetaminophen toxicity in cats?
- Activated charcoal alone
- N-acetylcysteine (NAC) (Correct answer)
- Vitamin K1
- Atropine
Correct answer: N-acetylcysteine (NAC)
N-acetylcysteine replenishes glutathione stores, allowing detoxification of the toxic acetaminophen metabolite NAPQI and is the primary antidote for acetaminophen toxicity.
Question 2: Organophosphate toxicity in animals is treated with which combination of drugs?
- Pralidoxime (2-PAM) alone
- Atropine and pralidoxime (2-PAM) (Correct answer)
- Naloxone and flumazenil
- Physostigmine and diazepam
Correct answer: Atropine and pralidoxime (2-PAM)
Atropine blocks muscarinic signs of organophosphate toxicity while pralidoxime reactivates acetylcholinesterase if given early before 'aging' of the enzyme occurs.
Question 3: Which of the following correctly describes 'first-pass metabolism'?
- Drug elimination by the kidneys after IV administration
- Hepatic metabolism that reduces bioavailability of orally administered drugs before reaching systemic circulation (Correct answer)
- The initial drug distribution phase immediately after IV injection
- Metabolism occurring in the GI lumen before absorption
Correct answer: Hepatic metabolism that reduces bioavailability of orally administered drugs before reaching systemic circulation
First-pass metabolism refers to the hepatic biotransformation of an orally administered drug as it passes through the portal circulation before reaching systemic circulation, reducing bioavailability.
Question 4: A bird (psittacine) presents with a bacterial infection. Which antibiotic class should be avoided due to risk of fatal dysbiosis?
- Fluoroquinolones
- Beta-lactams
- Aminoglycosides
- Lincosamides and macrolides at high doses (Correct answer)
Correct answer: Lincosamides and macrolides at high doses
Lincosamides (e.g., clindamycin) and certain macrolides can cause fatal disruption of the GI microbiome in birds, similar to the antibiotic-associated enterocolitis seen in other species.
Question 5: Which drug is used to treat urinary incontinence in spayed female dogs by increasing urethral sphincter tone?
- Prazosin
- Phenylpropanolamine (PPA) (Correct answer)
- Bethanechol
- Propranolol
Correct answer: Phenylpropanolamine (PPA)
Phenylpropanolamine is an alpha-adrenergic agonist that increases urethral sphincter muscle tone and is the drug of choice for hormone-responsive incontinence in spayed dogs.
Question 6: Which flea and tick preventive acts as a selective antagonist of insect GABA-gated chloride channels?
- Spinosad
- Fipronil (Correct answer)
- Imidacloprid
- Selamectin
Correct answer: Fipronil
Fipronil selectively blocks GABA-gated chloride channels in insects and arachnids, causing CNS hyperexcitability and death; it has low affinity for mammalian receptors.
Question 7: A horse with endotoxemia requires treatment with flunixin meglumine. What is the primary reason flunixin is preferred over other NSAIDs in this scenario?
- It is the most potent analgesic available for horses
- It effectively inhibits COX-mediated thromboxane production at low doses, reducing endotoxin-induced vascular effects (Correct answer)
- It crosses the blood-brain barrier more effectively than other NSAIDs
- It has the longest duration of action of any equine NSAID
Correct answer: It effectively inhibits COX-mediated thromboxane production at low doses, reducing endotoxin-induced vascular effects
Flunixin meglumine at low doses inhibits thromboxane synthesis and attenuates some hemodynamic effects of endotoxin, making it particularly beneficial in horses with endotoxemia.
NAVLE Veterinary Pharmacology 5
Which drug is the antidote for acetaminophen toxicity in cats?