NAPLEX QBANK Pharmacology and Drug Mechanisms 3 — Questions and Answers
Question 1: Statins lower cholesterol by inhibiting which enzyme?
- HMG-CoA reductase (Correct answer)
- Squalene synthase
- Lipoprotein lipase
- PCSK9
Correct answer: HMG-CoA reductase
Statins competitively inhibit HMG-CoA reductase, the rate-limiting enzyme of cholesterol synthesis.
Question 2: Which opioid is also an NMDA receptor antagonist, useful in neuropathic pain?
- Methadone (Correct answer)
- Morphine
- Codeine
- Hydromorphone
Correct answer: Methadone
Methadone provides mu-opioid agonism plus NMDA antagonism.
Question 3: The primary mechanism of proton pump inhibitors is:
- Irreversible inhibition of gastric H+/K+ ATPase (Correct answer)
- H2 receptor blockade
- Muscarinic M1 antagonism
- Neutralization of gastric acid
Correct answer: Irreversible inhibition of gastric H+/K+ ATPase
PPIs irreversibly block the parietal cell H+/K+ ATPase proton pump.
Question 4: Which drug class can cause hyperkalemia due to aldosterone antagonism?
- Potassium-sparing diuretics (Correct answer)
- Thiazide diuretics
- Loop diuretics
- Carbonic anhydrase inhibitors
Correct answer: Potassium-sparing diuretics
Spironolactone and similar agents block aldosterone, retaining potassium.
Question 5: Phenytoin exhibits which pharmacokinetic property at therapeutic doses?
- Zero-order (nonlinear) elimination (Correct answer)
- First-order elimination only
- No protein binding
- Renal elimination unchanged
Correct answer: Zero-order (nonlinear) elimination
Phenytoin shows saturable metabolism, so small dose changes cause large level swings.
Question 6: Which mechanism underlies the bronchodilation of tiotropium?
- Long-acting muscarinic receptor antagonism (Correct answer)
- Beta-2 agonism
- Leukotriene receptor blockade
- Mast cell stabilization
Correct answer: Long-acting muscarinic receptor antagonism
Tiotropium is a LAMA that blocks muscarinic receptors in airway smooth muscle.
Question 7: DPP-4 inhibitors such as sitagliptin lower glucose by:
- Preventing incretin (GLP-1) degradation (Correct answer)
- Blocking renal glucose reabsorption
- Stimulating glucagon release
- Inhibiting hepatic gluconeogenesis directly
Correct answer: Preventing incretin (GLP-1) degradation
DPP-4 inhibitors prolong incretin action, enhancing insulin secretion.
NAPLEX QBANK Pharmacology and Drug Mechanisms 3
Statins lower cholesterol by inhibiting which enzyme?