NR.210.602 Clinical Pharmacology
Comprehensive Final Exam (Qns & Ans)
2025
1. Case Scenario: A 65-year-old female with atrial fibrillation
has been on warfarin for stroke prophylaxis. After being started
on a course of a macrolide antibiotic for pneumonia, her
International Normalized Ratio (INR) increases markedly, placing
her at risk for bleeding. Which mechanism best explains this
interaction?
A. Increased warfarin clearance by enzyme induction
B. Inhibition of cytochrome P450 metabolism leading to
elevated warfarin levels
C. Competition for plasma protein binding, reducing
warfarin’s active fraction
D. Enhanced gastrointestinal absorption of warfarin
ANS: B. Inhibition of cytochrome P450 metabolism
leading to elevated warfarin levels
©2025
, Rationale: Many macrolide antibiotics inhibit CYP enzymes
(especially CYP3A4), reducing warfarin metabolism and thereby
increasing its plasma concentration and bleeding risk.
2. Case Scenario: A 50-year-old man with type 2 diabetes is
maintained on metformin. After commencement of a new
medication for gastroesophageal reflux disease, he experiences
gastrointestinal side effects and signs of metformin accumulation.
Which mechanism could account for this phenomenon?
A. Increased hepatic gluconeogenesis
B. Inhibition of the renal organic cation transporter (OCT2)
C. Induction of cytochrome P450 enzymes
D. Enhanced intestinal motility decreasing drug absorption
ANS: B. Inhibition of the renal organic cation transporter
(OCT2)
Rationale: Metformin is primarily cleared by renal tubular
secretion via OCT2. Inhibiting this transporter diminishes
clearance, increasing plasma levels and side effects.
3. Case Scenario: A patient with moderate liver impairment is
prescribed a drug that normally undergoes extensive first-pass
metabolism. How is the bioavailability of this drug most likely
affected in this patient?
A. It is lower than normal due to enhanced hepatic clearance.
©2025
, B. It is higher than normal because diminished first-pass
metabolism increases systemic availability.
C. It remains unchanged as first-pass metabolism only affects
inactive forms.
D. It varies unpredictably regardless of liver function.
ANS: B. It is higher than normal because diminished first-
pass metabolism increases systemic availability.
Rationale: Liver impairment reduces first-pass metabolism,
resulting in a greater fraction of the drug entering systemic
circulation and thereby increasing its bioavailability.
4. Case Scenario: A 30-year-old female diagnosed with
depression is initiated on a selective serotonin reuptake inhibitor
(SSRI). Which cytochrome P450 isoenzyme is most commonly
involved in the metabolism of many SSRIs, affecting potential
drug interactions?
A. CYP1A2
B. CYP2D6
C. CYP3A4
D. CYP2C19
ANS: B. CYP2D6
Rationale: Several SSRIs (e.g., fluoxetine, paroxetine) are
metabolized primarily by CYP2D6, making this enzyme critical
in understanding their interaction profiles.
©2025
Comprehensive Final Exam (Qns & Ans)
2025
1. Case Scenario: A 65-year-old female with atrial fibrillation
has been on warfarin for stroke prophylaxis. After being started
on a course of a macrolide antibiotic for pneumonia, her
International Normalized Ratio (INR) increases markedly, placing
her at risk for bleeding. Which mechanism best explains this
interaction?
A. Increased warfarin clearance by enzyme induction
B. Inhibition of cytochrome P450 metabolism leading to
elevated warfarin levels
C. Competition for plasma protein binding, reducing
warfarin’s active fraction
D. Enhanced gastrointestinal absorption of warfarin
ANS: B. Inhibition of cytochrome P450 metabolism
leading to elevated warfarin levels
©2025
, Rationale: Many macrolide antibiotics inhibit CYP enzymes
(especially CYP3A4), reducing warfarin metabolism and thereby
increasing its plasma concentration and bleeding risk.
2. Case Scenario: A 50-year-old man with type 2 diabetes is
maintained on metformin. After commencement of a new
medication for gastroesophageal reflux disease, he experiences
gastrointestinal side effects and signs of metformin accumulation.
Which mechanism could account for this phenomenon?
A. Increased hepatic gluconeogenesis
B. Inhibition of the renal organic cation transporter (OCT2)
C. Induction of cytochrome P450 enzymes
D. Enhanced intestinal motility decreasing drug absorption
ANS: B. Inhibition of the renal organic cation transporter
(OCT2)
Rationale: Metformin is primarily cleared by renal tubular
secretion via OCT2. Inhibiting this transporter diminishes
clearance, increasing plasma levels and side effects.
3. Case Scenario: A patient with moderate liver impairment is
prescribed a drug that normally undergoes extensive first-pass
metabolism. How is the bioavailability of this drug most likely
affected in this patient?
A. It is lower than normal due to enhanced hepatic clearance.
©2025
, B. It is higher than normal because diminished first-pass
metabolism increases systemic availability.
C. It remains unchanged as first-pass metabolism only affects
inactive forms.
D. It varies unpredictably regardless of liver function.
ANS: B. It is higher than normal because diminished first-
pass metabolism increases systemic availability.
Rationale: Liver impairment reduces first-pass metabolism,
resulting in a greater fraction of the drug entering systemic
circulation and thereby increasing its bioavailability.
4. Case Scenario: A 30-year-old female diagnosed with
depression is initiated on a selective serotonin reuptake inhibitor
(SSRI). Which cytochrome P450 isoenzyme is most commonly
involved in the metabolism of many SSRIs, affecting potential
drug interactions?
A. CYP1A2
B. CYP2D6
C. CYP3A4
D. CYP2C19
ANS: B. CYP2D6
Rationale: Several SSRIs (e.g., fluoxetine, paroxetine) are
metabolized primarily by CYP2D6, making this enzyme critical
in understanding their interaction profiles.
©2025
