Feline Pharmacology and Toxicology Flashcards

Which antiparasitic drug is safe to use in cats at antiparasitic doses but causes toxicity at high doses due to P-glycoprotein substrate status?

Answer: Ivermectin

Ivermectin is a P-gp substrate; while cats generally express functional MDR1/ABCB1 and tolerate antiparasitic doses, high doses can overwhelm the blood-brain barrier protection causing CNS toxicity.

A cat receiving chlorambucil for IBD develops acute cerebellar signs. What is the likely cause?

Answer: Chlorambucil-induced neurotoxicity

Chlorambucil can cause reversible neurotoxicity (tremors, myoclonus, seizures) in cats, particularly at higher doses; dose reduction or discontinuation typically resolves signs.

Which antibiotic is associated with fatal hepatic necrosis in cats and should be avoided?

Answer: Tetracycline

Tetracyclines, especially doxycycline, can cause esophageal strictures and hepatotoxicity in cats; oral tablets must always be followed with a water bolus to prevent esophageal damage.

What is the primary risk of administering xylazine to cats compared to dogs?

Answer: Cats are more sensitive and show profound cardiovascular depression at lower doses

Cats are approximately 10 times more sensitive to xylazine than dogs, achieving deep sedation at doses that cause only mild sedation in dogs, along with significant cardiovascular and respiratory depression.

Which drug used in cats for urethral spasm has sympathomimetic properties that can cause hypertension?

Answer: Pseudoephedrine

Pseudoephedrine, while occasionally used off-label for urinary incontinence, is a sympathomimetic that can cause hypertension, tachycardia, and CNS stimulation in cats.

A cat is diagnosed with hyperthyroidism. Which drug is a thioureylene antithyroid agent used for medical management?

Answer: Methimazole

Methimazole (Felimazole) inhibits thyroid peroxidase, blocking thyroid hormone synthesis; it is the primary medical treatment for feline hyperthyroidism but can cause facial pruritus and hepatotoxicity.

Which common food item is toxic to cats because it contains disulfide compounds causing Heinz body hemolytic anemia?

Answer: Onion and garlic

Onions, garlic, and related Allium species contain n-propyl disulfide which oxidizes feline hemoglobin, forming Heinz bodies and causing hemolytic anemia; cats are more sensitive than dogs.