NAPLEX QBANK Pharmacology and Mechanism of Action 2 — Questions and Answers
Question 1: A patient on warfarin starts amiodarone. What is the primary mechanism of the resulting increased INR?
- Inhibition of CYP2C9 metabolism of warfarin (Correct answer)
- Displacement of warfarin from albumin only
- Induction of vitamin K epoxide reductase
- Increased renal clearance of warfarin
Correct answer: Inhibition of CYP2C9 metabolism of warfarin
Amiodarone inhibits CYP2C9 (and CYP3A4), reducing warfarin metabolism and raising INR.
Question 2: Which mechanism explains why ACE inhibitors can cause a dry cough?
- Accumulation of bradykinin and substance P (Correct answer)
- Direct beta-2 receptor blockade
- Increased angiotensin II levels
- Histamine release from mast cells
Correct answer: Accumulation of bradykinin and substance P
ACE normally degrades bradykinin, so its inhibition raises bradykinin levels, triggering cough.
Question 3: Metformin's primary glucose-lowering mechanism is best described as:
- Decreasing hepatic gluconeogenesis (Correct answer)
- Stimulating pancreatic insulin secretion
- Blocking intestinal alpha-glucosidase
- Inhibiting SGLT2 in the kidney
Correct answer: Decreasing hepatic gluconeogenesis
Metformin chiefly reduces hepatic glucose production via AMPK activation.
Question 4: Which drug class works by irreversibly inhibiting the proton pump (H+/K+ ATPase)?
- Proton pump inhibitors (Correct answer)
- H2-receptor antagonists
- Antacids
- Prostaglandin analogs
Correct answer: Proton pump inhibitors
PPIs covalently bind and irreversibly inhibit gastric H+/K+ ATPase.
Question 5: The antiplatelet effect of clopidogrel requires which step?
- CYP2C19 activation to its active metabolite (Correct answer)
- Direct reversible binding to P2Y12
- Conversion by gut bacteria
- Inhibition of cyclooxygenase-1
Correct answer: CYP2C19 activation to its active metabolite
Clopidogrel is a prodrug activated mainly by CYP2C19; poor metabolizers respond less.
Question 6: Which mechanism underlies the bronchodilation produced by albuterol?
- Beta-2 adrenergic receptor agonism increasing cAMP (Correct answer)
- Muscarinic receptor antagonism
- Phosphodiesterase inhibition
- Leukotriene receptor blockade
Correct answer: Beta-2 adrenergic receptor agonism increasing cAMP
Albuterol stimulates beta-2 receptors, raising cAMP and relaxing airway smooth muscle.
Question 7: Statins lower LDL primarily by:
- Inhibiting HMG-CoA reductase and upregulating LDL receptors (Correct answer)
- Binding bile acids in the intestine
- Blocking intestinal cholesterol absorption
- Inhibiting PCSK9
Correct answer: Inhibiting HMG-CoA reductase and upregulating LDL receptors
Statins inhibit HMG-CoA reductase, lowering intracellular cholesterol and upregulating hepatic LDL receptors.
NAPLEX QBANK Pharmacology and Mechanism of Action 2
A patient on warfarin starts amiodarone.
What is the primary mechanism of the resulting increased INR?