DVM Doctor of Veterinary Medicine Veterinary Pharmacology and Therapeutics Questions and Answers — Questions and Answers
Question 1: A 4-month-old, 20 kg Labrador Retriever puppy is diagnosed with a bacterial urinary tract infection. The owner has financial constraints and declines a urine culture and sensitivity. Which of the following antimicrobials should be AVOIDED as an empirical choice due to the risk of inducing arthropathy in a growing dog?
- Cephalexin
- Amoxicillin-clavulanate
- Enrofloxacin (Correct answer)
- Trimethoprim-sulfadiazine
Correct answer: Enrofloxacin
Enrofloxacin is a fluoroquinolone antibiotic. This class of drugs has been shown to cause damage to the articular cartilage (arthropathy) in growing, large-breed dogs. The other options, including cephalosporins (Cephalexin), potentiated penicillins (Amoxicillin-clavulanate), and potentiated sulfonamides (Trimethoprim-sulfadiazine), do not carry this specific risk and are generally considered safer choices for skeletally immature patients.
Question 2: Which of the following is the most common and clinically significant adverse effect associated with phenylbutazone administration in horses?
- Right dorsal colitis (Correct answer)
- Laminitis
- Hepatotoxicity
- Aplastic anemia
Correct answer: Right dorsal colitis
Phenylbutazone is a non-selective NSAID that inhibits both COX-1 and COX-2 enzymes. The inhibition of COX-1 reduces the production of protective prostaglandins in the gastrointestinal tract, which can lead to mucosal damage. The right dorsal colon is particularly susceptible to this ischemic injury, resulting in ulceration, protein loss, and colic. While renal toxicity can occur, especially with dehydration, and other side effects are possible, right dorsal colitis is the most classic and feared complication.
Question 3: A 7-year-old Doberman Pinscher is diagnosed with preclinical (occult) dilated cardiomyopathy (DCM) via an echocardiogram which reveals significant left ventricular dilation in systole. The dog is currently asymptomatic. Based on the findings of the PROTECT study, which medication is indicated to delay the onset of congestive heart failure and prolong survival?
- Furosemide
- Pimobendan (Correct answer)
- Atenolol
- Enalapril
Correct answer: Pimobendan
The PROTECT study was a landmark clinical trial which demonstrated that administering pimobendan to Doberman Pinschers with preclinical (occult) DCM significantly prolonged the time to the onset of congestive heart failure and extended overall survival time. Furosemide is a diuretic used to treat active congestive heart failure, not prevent it. Enalapril is an ACE inhibitor often used in heart disease, but pimobendan was shown to be superior for this specific indication. Atenolol is a beta-blocker sometimes used for arrhythmias but is not the primary treatment to delay heart failure in this context.
Question 4: A 5-year-old indoor cat is presented for emergency evaluation. The owner reports administering a single dose of an over-the-counter human pain reliever 12 hours ago. The cat is lethargic, with facial edema and muddy, cyanotic mucous membranes. These clinical signs are most consistent with toxicity from which drug, and what is the primary therapeutic antidote?
- Ibuprofen; Misoprostol
- Aspirin; Vitamin K1
- Acetaminophen; N-acetylcysteine (Correct answer)
- Naproxen; Omeprazole
Correct answer: Acetaminophen; N-acetylcysteine
Cats have a deficiency in the glucuronidation pathway for drug metabolism, making them extremely susceptible to acetaminophen (paracetamol) toxicity. A toxic metabolite accumulates, causing oxidative damage to red blood cells, leading to the characteristic methemoglobinemia (muddy/brown mucous membranes), as well as facial and paw edema and hepatotoxicity. The specific antidote is N-acetylcysteine (NAC), which replenishes glutathione stores needed to neutralize the toxic metabolite.
Question 5: What is the primary mechanism of action for the antiemetic drug maropitant?
- Dopamine (D2) receptor antagonist in the chemoreceptor trigger zone (CRTZ)
- Serotonin (5-HT3) receptor antagonist on vagal afferent nerves
- H1-histamine receptor antagonist in the vestibular nucleus
- Neurokinin-1 (NK1) receptor antagonist in the emetic center (Correct answer)
Correct answer: Neurokinin-1 (NK1) receptor antagonist in the emetic center
Maropitant is a neurokinin-1 (NK1) receptor antagonist. It works by blocking the binding of Substance P, a key neurotransmitter, to NK1 receptors located centrally in the emetic center of the brain. This blockade inhibits the final common pathway for vomiting, making it a very broad-spectrum and effective antiemetic against both central and peripheral causes of vomiting. Metoclopramide is a D2 antagonist, ondansetron is a 5-HT3 antagonist, and diphenhydramine is an H1 antagonist.
Question 6: Which of the following statements regarding extra-label drug use (ELDU) in food-producing animals in the United States is correct?
- A veterinarian may use a drug extra-label if it is more cost-effective than the approved labeled drug.
- ELDU is permitted for production purposes, such as improving feed efficiency.
- Phenylbutazone is prohibited from extra-label use in female dairy cattle 20 months of age or older. (Correct answer)
- It is permissible to use any approved human drug in a food animal if a veterinarian deems it necessary.
Correct answer: Phenylbutazone is prohibited from extra-label use in female dairy cattle 20 months of age or older.
The Animal Medicinal Drug Use Clarification Act (AMDUCA) strictly regulates ELDU in food animals to protect the human food supply. Several drugs are explicitly prohibited from ELDU in certain species due to public health risks. Phenylbutazone is banned for ELDU in female dairy cattle 20 months of age or older because of the risk of residues causing aplastic anemia in humans. ELDU is not permitted for cost reasons or for production purposes, and there are restrictions on using human drugs if an approved animal drug can be used instead.
DVM Doctor of Veterinary Medicine Veterinary Pharmacology and Therapeutics Questions and Answers
A 4-month-old, 20 kg Labrador Retriever puppy is diagnosed with a bacterial urinary tract infection.
The owner has financial constraints and declines a urine culture and sensitivity.
Which of the following antimicrobials should be AVOIDED as an empirical choice due to the risk of inducing arthropathy in a growing dog?