, Question 1
A patient with heart failure and reduced ejection fraction (HFrEF) is initiated
on sacubitril/valsartan. Which mechanism best explains why this agent must
not be co-administered with an ACE inhibitor within 36 hours?
A. Additive bradykinin accumulation from dual neprilysin and ACE
inhibition increases angioedema risk.
B. Sacubitril inhibits ACE, leading to unopposed angiotensin II effects
and hypertension.
C. Valsartan blocks AT1 receptors, causing reflex tachycardia that negates
sacubitril's benefit.
D. Combined therapy reduces renal perfusion by inhibiting prostaglandin
synthesis.
Correct Answer: A - Additive bradykinin accumulation from
dual neprilysin and ACE inhibition increases angioedema risk.
RATIONALE
Sacubitril inhibits neprilysin, which degrades bradykinin; concurrent
ACE inhibition also raises bradykinin, markedly increasing
angioedema risk. Option B is false because sacubitril does not inhibit
ACE. Option C is incorrect because reflex tachycardia is not the
primary concern and valsartan does not negate sacubitril's benefit.
Option D is unrelated; prostaglandin synthesis is not the mechanism.
Question 2
Which pathophysiologic alteration best explains the development of
hyperkalemia in a patient with metabolic acidosis and insulin deficiency?
A. Increased renal potassium excretion due to aldosterone excess
B. Extracellular shift of potassium via H+/K+ exchange and reduced
cellular uptake
C. Enhanced sodium-potassium ATPase activity driving potassium
intracellularly
D. Decreased gastrointestinal potassium absorption
Page 2
,Correct Answer: B - Extracellular shift of potassium via H+/K+
exchange and reduced cellular uptake
RATIONALE
In acidosis, hydrogen ions move into cells in exchange for potassium
moving out; insulin deficiency further impairs cellular potassium
uptake, causing hyperkalemia. Option A is wrong because aldosterone
excess would lower potassium. Option C would lower serum
potassium. Option D does not cause hyperkalemia; reduced GI
absorption would lower potassium.
Question 3
A patient on warfarin for atrial fibrillation is prescribed
trimethoprim-sulfamethoxazole for a urinary tract infection. Which
pharmacokinetic interaction is most likely to occur?
A. Induction of CYP2C9, decreasing INR and thromboembolic risk
B. Inhibition of CYP2C9, increasing INR and bleeding risk
C. Increased renal clearance of warfarin, reducing its effect
D. Displacement from albumin without altering free drug concentration
Correct Answer: B - Inhibition of CYP2C9, increasing INR and
bleeding risk
RATIONALE
Trimethoprim-sulfamethoxazole inhibits CYP2C9, the enzyme
metabolizing S-warfarin, leading to increased INR and bleeding risk.
Option A is incorrect because induction would decrease INR. Option
C is wrong; renal clearance is not the primary mechanism. Option D is
incorrect because displacement alone does not usually cause a
sustained increase in free drug unless metabolism is also inhibited.
Page 3
, Question 4
A patient with type 2 diabetes and chronic kidney disease (eGFR 32
mL/min/1.73 m²) is on metformin. Which action is most appropriate according
to current FDA labeling and clinical guidelines?
A. Continue metformin at current dose with routine monitoring.
B. Discontinue metformin and initiate an SGLT2 inhibitor.
C. Reduce metformin dose by 50% and recheck eGFR in 3 months.
D. Switch to a sulfonylurea due to renal safety.
Correct Answer: B - Discontinue metformin and initiate an
SGLT2 inhibitor.
RATIONALE
Metformin is contraindicated when eGFR is below 30 mL/min/1.73
m² and should not be initiated; at eGFR 32, many guidelines
recommend discontinuation or dose reduction, but an SGLT2 inhibitor
is preferred for renal and cardiovascular protection. Option A is
unsafe. Option C is not aligned with current recommendations. Option
D is less optimal because sulfonylureas risk hypoglycemia in CKD.
Question 5
Which statement best describes the concept of 'therapeutic index' and its
clinical implication for prescribing?
A. A high therapeutic index indicates a narrow margin between
therapeutic and toxic doses.
B. A low therapeutic index requires routine therapeutic drug monitoring
to avoid toxicity.
C. Therapeutic index is calculated as the median toxic dose divided by
the median effective dose.
D. Drugs with a low therapeutic index are safer because they have fewer
side effects.
Correct Answer: B - A low therapeutic index requires routine
Page 4
A patient with heart failure and reduced ejection fraction (HFrEF) is initiated
on sacubitril/valsartan. Which mechanism best explains why this agent must
not be co-administered with an ACE inhibitor within 36 hours?
A. Additive bradykinin accumulation from dual neprilysin and ACE
inhibition increases angioedema risk.
B. Sacubitril inhibits ACE, leading to unopposed angiotensin II effects
and hypertension.
C. Valsartan blocks AT1 receptors, causing reflex tachycardia that negates
sacubitril's benefit.
D. Combined therapy reduces renal perfusion by inhibiting prostaglandin
synthesis.
Correct Answer: A - Additive bradykinin accumulation from
dual neprilysin and ACE inhibition increases angioedema risk.
RATIONALE
Sacubitril inhibits neprilysin, which degrades bradykinin; concurrent
ACE inhibition also raises bradykinin, markedly increasing
angioedema risk. Option B is false because sacubitril does not inhibit
ACE. Option C is incorrect because reflex tachycardia is not the
primary concern and valsartan does not negate sacubitril's benefit.
Option D is unrelated; prostaglandin synthesis is not the mechanism.
Question 2
Which pathophysiologic alteration best explains the development of
hyperkalemia in a patient with metabolic acidosis and insulin deficiency?
A. Increased renal potassium excretion due to aldosterone excess
B. Extracellular shift of potassium via H+/K+ exchange and reduced
cellular uptake
C. Enhanced sodium-potassium ATPase activity driving potassium
intracellularly
D. Decreased gastrointestinal potassium absorption
Page 2
,Correct Answer: B - Extracellular shift of potassium via H+/K+
exchange and reduced cellular uptake
RATIONALE
In acidosis, hydrogen ions move into cells in exchange for potassium
moving out; insulin deficiency further impairs cellular potassium
uptake, causing hyperkalemia. Option A is wrong because aldosterone
excess would lower potassium. Option C would lower serum
potassium. Option D does not cause hyperkalemia; reduced GI
absorption would lower potassium.
Question 3
A patient on warfarin for atrial fibrillation is prescribed
trimethoprim-sulfamethoxazole for a urinary tract infection. Which
pharmacokinetic interaction is most likely to occur?
A. Induction of CYP2C9, decreasing INR and thromboembolic risk
B. Inhibition of CYP2C9, increasing INR and bleeding risk
C. Increased renal clearance of warfarin, reducing its effect
D. Displacement from albumin without altering free drug concentration
Correct Answer: B - Inhibition of CYP2C9, increasing INR and
bleeding risk
RATIONALE
Trimethoprim-sulfamethoxazole inhibits CYP2C9, the enzyme
metabolizing S-warfarin, leading to increased INR and bleeding risk.
Option A is incorrect because induction would decrease INR. Option
C is wrong; renal clearance is not the primary mechanism. Option D is
incorrect because displacement alone does not usually cause a
sustained increase in free drug unless metabolism is also inhibited.
Page 3
, Question 4
A patient with type 2 diabetes and chronic kidney disease (eGFR 32
mL/min/1.73 m²) is on metformin. Which action is most appropriate according
to current FDA labeling and clinical guidelines?
A. Continue metformin at current dose with routine monitoring.
B. Discontinue metformin and initiate an SGLT2 inhibitor.
C. Reduce metformin dose by 50% and recheck eGFR in 3 months.
D. Switch to a sulfonylurea due to renal safety.
Correct Answer: B - Discontinue metformin and initiate an
SGLT2 inhibitor.
RATIONALE
Metformin is contraindicated when eGFR is below 30 mL/min/1.73
m² and should not be initiated; at eGFR 32, many guidelines
recommend discontinuation or dose reduction, but an SGLT2 inhibitor
is preferred for renal and cardiovascular protection. Option A is
unsafe. Option C is not aligned with current recommendations. Option
D is less optimal because sulfonylureas risk hypoglycemia in CKD.
Question 5
Which statement best describes the concept of 'therapeutic index' and its
clinical implication for prescribing?
A. A high therapeutic index indicates a narrow margin between
therapeutic and toxic doses.
B. A low therapeutic index requires routine therapeutic drug monitoring
to avoid toxicity.
C. Therapeutic index is calculated as the median toxic dose divided by
the median effective dose.
D. Drugs with a low therapeutic index are safer because they have fewer
side effects.
Correct Answer: B - A low therapeutic index requires routine
Page 4
