NAPLEX QBANK Pharmacology and Mechanism of Action 3 — Questions and Answers
Question 1: Which antibiotic mechanism is associated with inhibition of the 50S ribosomal subunit?
- Macrolides such as azithromycin (Correct answer)
- Fluoroquinolones such as ciprofloxacin
- Aminoglycosides such as gentamicin
- Beta-lactams such as amoxicillin
Correct answer: Macrolides such as azithromycin
Macrolides bind the 50S subunit to block bacterial protein synthesis.
Question 2: Phenytoin exerts its antiseizure effect mainly by:
- Blocking voltage-gated sodium channels (Correct answer)
- Enhancing GABA-A chloride influx
- Blocking T-type calcium channels
- Antagonizing NMDA receptors
Correct answer: Blocking voltage-gated sodium channels
Phenytoin stabilizes inactivated sodium channels, reducing repetitive neuronal firing.
Question 3: Why must aminoglycosides be dosed carefully with monitoring?
- Narrow therapeutic index with nephro- and ototoxicity (Correct answer)
- They are CYP3A4 inducers
- They cause QT prolongation primarily
- They are highly protein bound
Correct answer: Narrow therapeutic index with nephro- and ototoxicity
Aminoglycosides have a narrow therapeutic index, risking nephrotoxicity and ototoxicity.
Question 4: Which drug increases insulin secretion by closing pancreatic K-ATP channels?
- Glipizide (sulfonylurea) (Correct answer)
- Pioglitazone
- Acarbose
- Empagliflozin
Correct answer: Glipizide (sulfonylurea)
Sulfonylureas close beta-cell K-ATP channels, depolarizing the cell to trigger insulin release.
Question 5: The mechanism of action of digoxin includes:
- Inhibition of Na+/K+ ATPase increasing intracellular calcium (Correct answer)
- Blockade of beta-1 adrenergic receptors
- Calcium channel blockade in the AV node only
- Direct ACE inhibition
Correct answer: Inhibition of Na+/K+ ATPase increasing intracellular calcium
Digoxin inhibits Na+/K+ ATPase, raising intracellular calcium and increasing contractility.
Question 6: Which class blocks angiotensin II at the AT1 receptor without raising bradykinin?
- ARBs such as losartan (Correct answer)
- ACE inhibitors such as lisinopril
- Direct renin inhibitors such as aliskiren
- Aldosterone antagonists such as spironolactone
Correct answer: ARBs such as losartan
ARBs block AT1 receptors directly, so they cause less cough than ACE inhibitors.
Question 7: SSRIs relieve depression by:
- Blocking presynaptic serotonin reuptake transporters (Correct answer)
- Inhibiting monoamine oxidase
- Blocking dopamine D2 receptors
- Agonizing GABA-B receptors
Correct answer: Blocking presynaptic serotonin reuptake transporters
SSRIs inhibit the serotonin transporter (SERT), increasing synaptic serotonin.
NAPLEX QBANK Pharmacology and Mechanism of Action 3
Which antibiotic mechanism is associated with inhibition of the 50S ribosomal subunit?