COMSAE Phase 2 BSA – Pharmacology and Therapeutics
Exam Review with Questions, Answers and Rationales
2026/2027 Update
Section 1: Autonomic and Cardiovascular Pharmacology
Question 1
A 58-year-old man with a history of essential hypertension and stable angina is initiated on a
new antihypertensive medication. Two weeks later, he presents to the clinic complaining of a
persistent, dry, hacking cough. Laboratory studies show normal renal function and electrolytes.
What is the pharmacological mechanism responsible for this adverse effect?
A. Accumulation of bradykinin and substance P due to inhibition of angiotensin-converting
enzyme
B. Direct stimulation of H1 histamine receptors in the bronchial tree by the drug metabolite
C. Reflex beta-2 receptor blockade leading to smooth muscle bronchoconstriction
D. Upregulation of alpha-1 adrenergic receptors in the upper respiratory tract
Correct Answer: A. Accumulation of bradykinin and substance P due to inhibition of
angiotensin-converting enzyme
Rationale: ACE inhibitors (e.g., lisinopril, enalapril) block the conversion of angiotensin I to
angiotensin II and simultaneously inhibit kininase II, the enzyme responsible for the degradation
of bradykinin and substance P. The resulting accumulation of bradykinin and substance P in the
lungs causes the characteristic dry cough seen in up to twenty percent of patients.
Question 2
A 65-year-old man is brought to the emergency department after experiencing acute chest pain
radiating to his jaw. Electrocardiogram reveals ST-segment elevations in leads II, III, and aVF.
He is administered sublingual nitroglycerin, which relieves his chest pain.
What is the primary cellular mechanism of action of nitrates in relieving myocardial
ischemia?
A. Conversion to nitric oxide, leading to activation of guanylyl cyclase, increased
intracellular cGMP, and vascular smooth muscle relaxation
, B. Blockade of L-type calcium channels in vascular smooth muscle cells, preventing calcium
influx
C. Inhibition of HMG-CoA reductase, acutely improving endothelial nitric oxide production
D. Stimulation of beta-2 adrenergic receptors, causing direct coronary artery vasodilation
Correct Answer: A. Conversion to nitric oxide, leading to activation of guanylyl cyclase,
increased intracellular cGMP, and vascular smooth muscle relaxation
Rationale: Organic nitrates act as prodrugs that release nitric oxide (NO) in vascular smooth
muscle. NO activates soluble guanylyl cyclase, increasing cyclic GMP (cGMP), which
dephosphorylates myosin light chains and leads to smooth muscle relaxation. Venodilation
predominates, reducing preload and myocardial oxygen demand.
Question 3
A 50-year-old woman with newly diagnosed essential hypertension is started on
hydrochlorothiazide.
What is the primary site and mechanism of action of thiazide diuretics in the nephron?
A. Inhibition of the sodium-chloride cotransporter in the early distal convoluted tubule
B. Inhibition of the Na+/K+/2Cl- cotransporter in the thick ascending limb of the loop of
Henle
C. Competitive antagonism of aldosterone receptors in the collecting duct
D. Blockade of epithelial sodium channels (ENaC) in the late distal tubule and collecting
duct
Correct Answer: A. Inhibition of the sodium-chloride cotransporter in the early distal
convoluted tubule
Rationale: Thiazide diuretics (e.g., hydrochlorothiazide) act primarily in the early distal
convoluted tubule by inhibiting the sodium-chloride (Na+-Cl-) cotransporter, decreasing sodium
reabsorption and promoting moderate sodium and water excretion.
Question 4
A 72-year-old man with chronic heart failure with reduced ejection fraction and atrial fibrillation
is prescribed digoxin.
What is the primary mechanism of action of digoxin in the treatment of heart failure?
, A. Inhibition of the Na+/K+-ATPase pump in myocardial cells, leading to increased
intracellular sodium, decreased sodium-calcium exchange, and increased intracellular
calcium availability
B. Direct stimulation of beta-1 adrenergic receptors to increase myocardial contractility
without altering heart rate
C. Blockade of muscarinic M2 receptors in the sinoatrial node to accelerate heart rate and
cardiac output
D. Inhibition of phosphodiesterase III, increasing cyclic AMP levels in cardiac and vascular
tissue
Correct Answer: A. Inhibition of the Na+/K+-ATPase pump in myocardial cells, leading to
increased intracellular sodium, decreased sodium-calcium exchange, and increased
intracellular calcium availability
Rationale: Digoxin inhibits the sarcolemmal Na+/K+-ATPase pump, raising intracellular
sodium concentration. This reduces the driving force for the Na+/Ca2+ exchanger, causing
intracellular calcium accumulation in the sarcoplasmic reticulum, which enhances inotropic
contractility. It also increases parasympathetic tone to slow heart rate.
Question 5
A 45-year-old man with hyperlipidemia is prescribed atorvastatin.
What is the primary biochemical mechanism of action of statins?
A. Competitive inhibition of HMG-CoA reductase, the rate-limiting enzyme in hepatic
cholesterol synthesis
B. Inhibition of intestinal cholesterol absorption via the NPC1L1 transporter
C. Activation of peroxisome proliferator-activated receptor alpha (PPAR-alpha) to increase
lipoprotein lipase activity
D. Binding to bile acids in the intestinal lumen to prevent their reabsorption
Correct Answer: A. Competitive inhibition of HMG-CoA reductase, the rate-limiting
enzyme in hepatic cholesterol synthesis
Rationale: Statins are competitive inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A
(HMG-CoA) reductase. By blocking the conversion of HMG-CoA to mevalonate, they decrease
hepatic cholesterol synthesis, upregulate LDL receptors on hepatocytes, and lower serum LDL
cholesterol levels.
, Section 2: Central Nervous System Pharmacology
Question 6
A 35-year-old woman with major depressive disorder is initiated on fluoxetine.
What is the primary pharmacological mechanism of action of selective serotonin reuptake
inhibitors (SSRIs)?
A. Inhibition of the presynaptic serotonin reuptake transporter (SERT), increasing
extracellular serotonin concentrations in the synaptic cleft
B. Irreversible inhibition of monoamine oxidase enzymes A and B
C. Antagonism of postsynaptic serotonin 5-HT2 and dopamine D2 receptors
D. Blockade of alpha-2 adrenergic autoreceptors to enhance norepinephrine release
Correct Answer: A. Inhibition of the presynaptic serotonin reuptake transporter (SERT),
increasing extracellular serotonin concentrations in the synaptic cleft
Rationale: SSRIs selectively inhibit the reuptake of serotonin by blocking the serotonin
transporter (SERT) located on presynaptic nerve terminals. This increases the availability of
serotonin within the synaptic cleft to bind postsynaptic receptors.
Question 7
A 28-year-old man with schizophrenia is treated with haloperidol. Several days later, he exhibits
severe muscle rigidity, high fever, autonomic instability, and altered mental status.
What is the primary pharmacological mechanism responsible for this adverse reaction?
A. Blockade of central dopamine D2 receptors in the nigrostriatal and hypothalamic
pathways
B. Overstimulation of central muscarinic acetylcholine receptors by excess acetylcholine
accumulation
C. Excessive blockade of central histamine H1 receptors leading to acute central nervous
system depression
D. Massive release of serotonin from presynaptic storage vesicles due to transporter reversal
Correct Answer: A. Blockade of central dopamine D2 receptors in the nigrostriatal and
hypothalamic pathways
Exam Review with Questions, Answers and Rationales
2026/2027 Update
Section 1: Autonomic and Cardiovascular Pharmacology
Question 1
A 58-year-old man with a history of essential hypertension and stable angina is initiated on a
new antihypertensive medication. Two weeks later, he presents to the clinic complaining of a
persistent, dry, hacking cough. Laboratory studies show normal renal function and electrolytes.
What is the pharmacological mechanism responsible for this adverse effect?
A. Accumulation of bradykinin and substance P due to inhibition of angiotensin-converting
enzyme
B. Direct stimulation of H1 histamine receptors in the bronchial tree by the drug metabolite
C. Reflex beta-2 receptor blockade leading to smooth muscle bronchoconstriction
D. Upregulation of alpha-1 adrenergic receptors in the upper respiratory tract
Correct Answer: A. Accumulation of bradykinin and substance P due to inhibition of
angiotensin-converting enzyme
Rationale: ACE inhibitors (e.g., lisinopril, enalapril) block the conversion of angiotensin I to
angiotensin II and simultaneously inhibit kininase II, the enzyme responsible for the degradation
of bradykinin and substance P. The resulting accumulation of bradykinin and substance P in the
lungs causes the characteristic dry cough seen in up to twenty percent of patients.
Question 2
A 65-year-old man is brought to the emergency department after experiencing acute chest pain
radiating to his jaw. Electrocardiogram reveals ST-segment elevations in leads II, III, and aVF.
He is administered sublingual nitroglycerin, which relieves his chest pain.
What is the primary cellular mechanism of action of nitrates in relieving myocardial
ischemia?
A. Conversion to nitric oxide, leading to activation of guanylyl cyclase, increased
intracellular cGMP, and vascular smooth muscle relaxation
, B. Blockade of L-type calcium channels in vascular smooth muscle cells, preventing calcium
influx
C. Inhibition of HMG-CoA reductase, acutely improving endothelial nitric oxide production
D. Stimulation of beta-2 adrenergic receptors, causing direct coronary artery vasodilation
Correct Answer: A. Conversion to nitric oxide, leading to activation of guanylyl cyclase,
increased intracellular cGMP, and vascular smooth muscle relaxation
Rationale: Organic nitrates act as prodrugs that release nitric oxide (NO) in vascular smooth
muscle. NO activates soluble guanylyl cyclase, increasing cyclic GMP (cGMP), which
dephosphorylates myosin light chains and leads to smooth muscle relaxation. Venodilation
predominates, reducing preload and myocardial oxygen demand.
Question 3
A 50-year-old woman with newly diagnosed essential hypertension is started on
hydrochlorothiazide.
What is the primary site and mechanism of action of thiazide diuretics in the nephron?
A. Inhibition of the sodium-chloride cotransporter in the early distal convoluted tubule
B. Inhibition of the Na+/K+/2Cl- cotransporter in the thick ascending limb of the loop of
Henle
C. Competitive antagonism of aldosterone receptors in the collecting duct
D. Blockade of epithelial sodium channels (ENaC) in the late distal tubule and collecting
duct
Correct Answer: A. Inhibition of the sodium-chloride cotransporter in the early distal
convoluted tubule
Rationale: Thiazide diuretics (e.g., hydrochlorothiazide) act primarily in the early distal
convoluted tubule by inhibiting the sodium-chloride (Na+-Cl-) cotransporter, decreasing sodium
reabsorption and promoting moderate sodium and water excretion.
Question 4
A 72-year-old man with chronic heart failure with reduced ejection fraction and atrial fibrillation
is prescribed digoxin.
What is the primary mechanism of action of digoxin in the treatment of heart failure?
, A. Inhibition of the Na+/K+-ATPase pump in myocardial cells, leading to increased
intracellular sodium, decreased sodium-calcium exchange, and increased intracellular
calcium availability
B. Direct stimulation of beta-1 adrenergic receptors to increase myocardial contractility
without altering heart rate
C. Blockade of muscarinic M2 receptors in the sinoatrial node to accelerate heart rate and
cardiac output
D. Inhibition of phosphodiesterase III, increasing cyclic AMP levels in cardiac and vascular
tissue
Correct Answer: A. Inhibition of the Na+/K+-ATPase pump in myocardial cells, leading to
increased intracellular sodium, decreased sodium-calcium exchange, and increased
intracellular calcium availability
Rationale: Digoxin inhibits the sarcolemmal Na+/K+-ATPase pump, raising intracellular
sodium concentration. This reduces the driving force for the Na+/Ca2+ exchanger, causing
intracellular calcium accumulation in the sarcoplasmic reticulum, which enhances inotropic
contractility. It also increases parasympathetic tone to slow heart rate.
Question 5
A 45-year-old man with hyperlipidemia is prescribed atorvastatin.
What is the primary biochemical mechanism of action of statins?
A. Competitive inhibition of HMG-CoA reductase, the rate-limiting enzyme in hepatic
cholesterol synthesis
B. Inhibition of intestinal cholesterol absorption via the NPC1L1 transporter
C. Activation of peroxisome proliferator-activated receptor alpha (PPAR-alpha) to increase
lipoprotein lipase activity
D. Binding to bile acids in the intestinal lumen to prevent their reabsorption
Correct Answer: A. Competitive inhibition of HMG-CoA reductase, the rate-limiting
enzyme in hepatic cholesterol synthesis
Rationale: Statins are competitive inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A
(HMG-CoA) reductase. By blocking the conversion of HMG-CoA to mevalonate, they decrease
hepatic cholesterol synthesis, upregulate LDL receptors on hepatocytes, and lower serum LDL
cholesterol levels.
, Section 2: Central Nervous System Pharmacology
Question 6
A 35-year-old woman with major depressive disorder is initiated on fluoxetine.
What is the primary pharmacological mechanism of action of selective serotonin reuptake
inhibitors (SSRIs)?
A. Inhibition of the presynaptic serotonin reuptake transporter (SERT), increasing
extracellular serotonin concentrations in the synaptic cleft
B. Irreversible inhibition of monoamine oxidase enzymes A and B
C. Antagonism of postsynaptic serotonin 5-HT2 and dopamine D2 receptors
D. Blockade of alpha-2 adrenergic autoreceptors to enhance norepinephrine release
Correct Answer: A. Inhibition of the presynaptic serotonin reuptake transporter (SERT),
increasing extracellular serotonin concentrations in the synaptic cleft
Rationale: SSRIs selectively inhibit the reuptake of serotonin by blocking the serotonin
transporter (SERT) located on presynaptic nerve terminals. This increases the availability of
serotonin within the synaptic cleft to bind postsynaptic receptors.
Question 7
A 28-year-old man with schizophrenia is treated with haloperidol. Several days later, he exhibits
severe muscle rigidity, high fever, autonomic instability, and altered mental status.
What is the primary pharmacological mechanism responsible for this adverse reaction?
A. Blockade of central dopamine D2 receptors in the nigrostriatal and hypothalamic
pathways
B. Overstimulation of central muscarinic acetylcholine receptors by excess acetylcholine
accumulation
C. Excessive blockade of central histamine H1 receptors leading to acute central nervous
system depression
D. Massive release of serotonin from presynaptic storage vesicles due to transporter reversal
Correct Answer: A. Blockade of central dopamine D2 receptors in the nigrostriatal and
hypothalamic pathways
