NBME Pharmacology Shelf Practice Exam Question s And Correct
Answers (Verified Answers) Plus Rationales 2026/2027 Q&A | Instant
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Question 1
A 52-year-old man with hypertension is started on lisinopril. Two weeks
later, routine blood work shows an increase in serum potassium from
4.2 mEq/L to 5.5 mEq/L. Which of the following physiological
mechanisms explains this medication-induced change?
• A) Direct blockade of epithelial sodium channels in the collecting
duct
• B) Inhibition of aldosterone-mediated sodium reabsorption and
potassium secretion
• C) Increased renin release due to loss of short-loop negative
feedback
• D) Upregulation of the Na+ /K+ /2Cl− cotransporter in the thick
ascending limb
• E) Competitive antagonism of mineralocorticoid receptors
Correct Answer: B
Rationale: ACE inhibitors like lisinopril block the conversion of
angiotensin I to angiotensin II. Because angiotensin II stimulates the
adrenal cortex to release aldosterone, lower angiotensin II levels lead to
reduced aldosterone. Aldosterone normally promotes luminal sodium
reabsorption and potassium/hydrogen ion secretion in the principal
cells of the cortical collecting tubule; its reduction leads to decreased
potassium excretion and hyperkalemia.
,Question 2
A 6-year-old boy is brought to the clinic by his mother because of
recurrent ear infections and is prescribed amoxicillin-clavulanate. The
addition of clavulanic acid to amoxicillin serves which of the following
pharmacological purposes?
• A) Prevents renal tubular secretion of amoxicillin, prolonging its
half-life
• B) Inhibits bacterial beta-lactamase enzymes that would
otherwise hydrolyze the beta-lactam ring of amoxicillin
• C) Binds to 30S ribosomal subunits to synergistically inhibit
bacterial protein synthesis
• D) Alters outer membrane permeability to increase intracellular
accumulation of the antibiotic
• E) Prevents the hepatic metabolism of amoxicillin via cytochrome
P450 inhibition
Correct Answer: B
Rationale: Certain bacteria develop resistance to beta-lactam antibiotics
by producing beta-lactamases (penicillinases) that cleave the beta-
lactam ring. Clavulanic acid is a beta-lactamase inhibitor that protects
amoxicillin from degradation.
Question 3
A 65-year-old man with Parkinson disease experiences severe motor
fluctuations and "on-off" episodes despite optimized
levodopa/carbidopa therapy. His neurologist decides to add a
medication that selectively inhibits monoamine oxidase type B (MAO-B)
,in the central nervous system. Which of the following drugs is most
appropriate?
• A) Entacapone
• B) Selegiline
• C) Benztropine
• D) Amantadine
• E) Ropinirole
Correct Answer: B
Rationale: Selegiline and rasagiline are selective MAO-B inhibitors that
block the breakdown of dopamine in the brain, thereby prolonging the
clinical efficacy of levodopa. Entacapone is a COMT inhibitor.
Benztropine is an anticholinergic. Amantadine enhances dopamine
release. Ropinirole is a dopamine agonist.
Question 4
A 55-year-old man is evaluated for poorly controlled type 2 diabetes
mellitus. He is started on a new glucose-lowering agent that acts as a
sodium-glucose cotransporter 2 (SGLT2) inhibitor. Which of the
following adverse effects is most commonly associated with this class of
medication?
• A) Hypoglycemia
• B) Lactic acidosis
• C) Genital mycotic infections and urinary tract infections
• D) Weight gain
, • E) Thyroid C-cell tumors
Correct Answer: C
Rationale: SGLT2 inhibitors (e.g., empagliflozin, dapagliflozin) block
glucose reabsorption in the proximal convoluted tubule, leading to
glucosuria. The presence of glucose in farm-like environments creates
an ideal medium for fungal and bacterial growth, increasing the risk of
vulvovaginal candidiasis, mycotic infections, and UTIs.
Question 5
A 34-year-old woman at 12 weeks gestation is diagnosed with Graves
disease. She is informed that treatment requires careful selection of
antithyroid medication due to distinct teratogenic risk profiles
associated with the available agents during the first trimester. Which of
the following drugs is preferred during the first trimester of pregnancy?
• A) Methimazole
• B) Propylthiouracil (PTU)
• C) Radioactive iodine ( 131I)
• D) Potassium iodide drops
• E) Propranolol monotherapy
Correct Answer: B
Rationale: Propylthiouracil (PTU) is preferred during the first trimester
of pregnancy because methimazole is associated with aplasia cutis and
choanal atresia (methimazole embryopathy). However, PTU carries a
risk of severe hepatotoxicity, so guidelines recommend switching back
to methimazole after the first trimester.
Answers (Verified Answers) Plus Rationales 2026/2027 Q&A | Instant
Download Pdf
Question 1
A 52-year-old man with hypertension is started on lisinopril. Two weeks
later, routine blood work shows an increase in serum potassium from
4.2 mEq/L to 5.5 mEq/L. Which of the following physiological
mechanisms explains this medication-induced change?
• A) Direct blockade of epithelial sodium channels in the collecting
duct
• B) Inhibition of aldosterone-mediated sodium reabsorption and
potassium secretion
• C) Increased renin release due to loss of short-loop negative
feedback
• D) Upregulation of the Na+ /K+ /2Cl− cotransporter in the thick
ascending limb
• E) Competitive antagonism of mineralocorticoid receptors
Correct Answer: B
Rationale: ACE inhibitors like lisinopril block the conversion of
angiotensin I to angiotensin II. Because angiotensin II stimulates the
adrenal cortex to release aldosterone, lower angiotensin II levels lead to
reduced aldosterone. Aldosterone normally promotes luminal sodium
reabsorption and potassium/hydrogen ion secretion in the principal
cells of the cortical collecting tubule; its reduction leads to decreased
potassium excretion and hyperkalemia.
,Question 2
A 6-year-old boy is brought to the clinic by his mother because of
recurrent ear infections and is prescribed amoxicillin-clavulanate. The
addition of clavulanic acid to amoxicillin serves which of the following
pharmacological purposes?
• A) Prevents renal tubular secretion of amoxicillin, prolonging its
half-life
• B) Inhibits bacterial beta-lactamase enzymes that would
otherwise hydrolyze the beta-lactam ring of amoxicillin
• C) Binds to 30S ribosomal subunits to synergistically inhibit
bacterial protein synthesis
• D) Alters outer membrane permeability to increase intracellular
accumulation of the antibiotic
• E) Prevents the hepatic metabolism of amoxicillin via cytochrome
P450 inhibition
Correct Answer: B
Rationale: Certain bacteria develop resistance to beta-lactam antibiotics
by producing beta-lactamases (penicillinases) that cleave the beta-
lactam ring. Clavulanic acid is a beta-lactamase inhibitor that protects
amoxicillin from degradation.
Question 3
A 65-year-old man with Parkinson disease experiences severe motor
fluctuations and "on-off" episodes despite optimized
levodopa/carbidopa therapy. His neurologist decides to add a
medication that selectively inhibits monoamine oxidase type B (MAO-B)
,in the central nervous system. Which of the following drugs is most
appropriate?
• A) Entacapone
• B) Selegiline
• C) Benztropine
• D) Amantadine
• E) Ropinirole
Correct Answer: B
Rationale: Selegiline and rasagiline are selective MAO-B inhibitors that
block the breakdown of dopamine in the brain, thereby prolonging the
clinical efficacy of levodopa. Entacapone is a COMT inhibitor.
Benztropine is an anticholinergic. Amantadine enhances dopamine
release. Ropinirole is a dopamine agonist.
Question 4
A 55-year-old man is evaluated for poorly controlled type 2 diabetes
mellitus. He is started on a new glucose-lowering agent that acts as a
sodium-glucose cotransporter 2 (SGLT2) inhibitor. Which of the
following adverse effects is most commonly associated with this class of
medication?
• A) Hypoglycemia
• B) Lactic acidosis
• C) Genital mycotic infections and urinary tract infections
• D) Weight gain
, • E) Thyroid C-cell tumors
Correct Answer: C
Rationale: SGLT2 inhibitors (e.g., empagliflozin, dapagliflozin) block
glucose reabsorption in the proximal convoluted tubule, leading to
glucosuria. The presence of glucose in farm-like environments creates
an ideal medium for fungal and bacterial growth, increasing the risk of
vulvovaginal candidiasis, mycotic infections, and UTIs.
Question 5
A 34-year-old woman at 12 weeks gestation is diagnosed with Graves
disease. She is informed that treatment requires careful selection of
antithyroid medication due to distinct teratogenic risk profiles
associated with the available agents during the first trimester. Which of
the following drugs is preferred during the first trimester of pregnancy?
• A) Methimazole
• B) Propylthiouracil (PTU)
• C) Radioactive iodine ( 131I)
• D) Potassium iodide drops
• E) Propranolol monotherapy
Correct Answer: B
Rationale: Propylthiouracil (PTU) is preferred during the first trimester
of pregnancy because methimazole is associated with aplasia cutis and
choanal atresia (methimazole embryopathy). However, PTU carries a
risk of severe hepatotoxicity, so guidelines recommend switching back
to methimazole after the first trimester.
