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NGR 6172 — Advanced Pharmacology
& Pharmacotherapeutics Practice
Examination 2026/2027.
DOMAIN 1: Pharmacokinetics, Pharmacodynamics & Drug Interactions
(14 Questions)
Question 1 (Multiple-Choice)
A 62-year-old male with coronary artery disease is prescribed clopidogrel 75 mg daily following
drug-eluting stent placement. The patient is also prescribed omeprazole 20 mg daily for GERD.
Genetic testing reveals the patient is a CYP2C19 *2/*2 poor metabolizer.
Which of the following best describes the clinical consequence of this pharmacogenomic
finding?
A) The patient will have excessive active metabolite formation, increasing bleeding risk. B) The
patient requires reduced clopidogrel dosing due to enhanced first-pass metabolism. C) The
patient is at increased risk of stent thrombosis due to inadequate bioactivation of clopidogrel.
D) The patient should switch to omeprazole 40 mg daily to enhance CYP2C19-mediated
conversion.
[CORRECT: C] Rationale: Clopidogrel is a prodrug that requires hepatic bioactivation by the
cytochrome P450 2C19 (CYP2C19) enzyme to form its active thiol metabolite, which irreversibly
inhibits the P2Y12 ADP receptor on platelets. A patient with a CYP2C19 *2/*2 loss-of-function
allele (poor metabolizer phenotype) cannot adequately convert clopidogrel to its active moiety,
resulting in diminished antiplatelet effect and a significantly increased risk of recurrent coronary
stent thrombosis. The concomitant omeprazole further inhibits CYP2C19, compounding the risk.
Evidence-based practice supports switching to prasugrel or ticagrelor in CYP2C19 poor
metabolizers.
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Question 2 (Multiple-Choice)
A patient with atrial fibrillation is prescribed amiodarone 400 mg daily. The patient also takes
simvastatin 80 mg daily for hyperlipidemia. The prescriber is concerned about an increased risk
of myopathy and rhabdomyolysis.
Which CYP450 enzyme is primarily responsible for this clinically significant drug-drug
interaction?
A) CYP1A2 B) CYP2D6 C) CYP3A4 D) CYP2C9
[CORRECT: C] Rationale: Simvastatin is a CYP3A4 substrate that undergoes extensive first-pass
hepatic metabolism. Amiodarone is a potent CYP3A4 inhibitor that reduces the hepatic
clearance of simvastatin, leading to increased systemic exposure, elevated serum simvastatin
acid levels, and a heightened risk of dose-dependent myopathy and rhabdomyolysis. The FDA
recommends limiting simvastatin to 20 mg daily when co-prescribed with amiodarone due to
this specific CYP3A4-mediated interaction.
Question 3 (SATA)
A 58-year-old patient with HIV is prescribed ritonavir-boosted darunavir. The patient also takes
the following medications. Which of the following medications are CYP3A4 substrates whose
serum concentrations would be significantly elevated by ritonavir, creating a risk for toxicity?
(Select all that apply)
A) Atorvastatin B) Warfarin C) Sildenafil D) Tacrolimus E) Metformin
[CORRECT: A, C, D] Rationale: Ritonavir is a potent CYP3A4 inhibitor used as a pharmacokinetic
booster in antiretroviral therapy. CYP3A4 substrates whose hepatic metabolism is significantly
inhibited by ritonavir include: Atorvastatin (increased risk of myopathy/rhabdomyolysis),
Sildenafil (increased risk of hypotension and priapism—dose must be reduced), and Tacrolimus
(increased risk of nephrotoxicity and neurotoxicity—requires close trough monitoring). Warfarin
is primarily a CYP2C9 substrate (with minor CYP3A4 involvement for the R-enantiomer).
Metformin is renally eliminated unchanged and does not undergo CYP450 metabolism.
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Question 4 (Calculation-Based)
A 70-year-old male (weight: 78 kg, height: 175 cm) is prescribed warfarin for atrial fibrillation.
His baseline INR is 1.0. After 5 days of warfarin 5 mg daily, his INR is 2.5. The therapeutic target
is INR 2.0–3.0. His weekly dose is currently 35 mg.
Using the linear dosing adjustment formula: New Weekly Dose = (Current Weekly Dose ×
Target INR) / Current INR
Calculate the new weekly warfarin dose and the new daily dose (rounded to the nearest 0.5
mg).
A) Weekly: 28 mg; Daily: 4 mg B) Weekly: 30.8 mg; Daily: 4.5 mg C) Weekly: 32 mg; Daily: 4.5 mg
D) Weekly: 35 mg; Daily: 5 mg (no change needed)
[CORRECT: A] Rationale: Formula: New Weekly Dose = (Current Weekly Dose × Target INR) /
Current INR
• Current Weekly Dose = 35 mg
• Target INR (midpoint) = 2.5
• Current INR = 2.5
Calculation: New Weekly Dose = (35 mg × 2.5) / 2.5 = 35 mg / 2.5 × 2.5 = 28 mg
However, since the patient is already at the therapeutic target (INR 2.5 falls within 2.0–3.0), the
prescriber may choose to maintain the current dose. But if targeting the lower bound (INR 2.0):
New Weekly Dose = (35 × 2.0) / 2.5 = 28 mg New Daily Dose = 28 mg / 7 = 4 mg
Warfarin has a narrow therapeutic index (TI ≈ 2–3), requiring precise INR monitoring and dose
titration to maintain therapeutic efficacy while minimizing bleeding risk.
Question 5 (Multiple-Choice)
A patient with community-acquired pneumonia is prescribed clarithromycin 500 mg BID. The
patient has a history of atrial fibrillation and takes fluconazole 200 mg daily for esophageal
candidiasis. The prescriber is concerned about QT prolongation.
Which statement accurately describes the mechanism of this drug-drug interaction?
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A) Fluconazole inhibits CYP2D6, reducing clarithromycin metabolism and increasing QT risk. B)
Fluconazole inhibits CYP3A4, reducing clarithromycin hepatic clearance and increasing the risk
of torsades de pointes. C) Clarithromycin inhibits fluconazole metabolism via CYP2C9, causing
additive cardiotoxicity. D) Both drugs are CYP3A4 inducers, causing increased active metabolite
formation and QT prolongation.
[CORRECT: B] Rationale: Clarithromycin is a CYP3A4 substrate that also inhibits the hERG
potassium channel (IKr), prolonging the QT interval. Fluconazole is a potent CYP3A4 inhibitor
that reduces the hepatic clearance of clarithromycin, leading to elevated serum clarithromycin
concentrations and an additive or synergistic risk of QT prolongation and torsades de pointes.
This is a classic example of a CYP3A4 inhibitor (fluconazole) increasing the systemic exposure
and cardiac toxicity of a CYP3A4 substrate (clarithromycin). Alternative macrolides with less QT
risk (azithromycin) or alternative antifungals should be considered.
Question 6 (Multiple-Choice)
A 45-year-old patient with chronic pain is prescribed tramadol 50 mg every 6 hours PRN.
Genetic testing reveals the patient is a CYP2D6 ultra-rapid metabolizer (UM).
What is the primary clinical concern with tramadol prescribing in this patient?
A) The patient will not convert tramadol to its active metabolite and will have inadequate
analgesia. B) The patient will rapidly convert tramadol to O-desmethyltramadol (M1), increasing
the risk of opioid toxicity and respiratory depression. C) The patient requires a prodrug activator
to enhance CYP2D6 function. D) The patient should receive tramadol ER to bypass first-pass
metabolism.
[CORRECT: B] Rationale: Tramadol is a prodrug that requires CYP2D6-mediated O-
demethylation to form its active metabolite, O-desmethyltramadol (M1), which has
approximately 200-fold greater mu-opioid receptor affinity than the parent drug. A CYP2D6
ultra-rapid metabolizer (UM) genotype (e.g., *1×N/*1×N) results in excessively rapid and
complete bioactivation, leading to supratherapeutic M1 concentrations, increased opioid
toxicity (respiratory depression, sedation, seizures), and potential fatality. Tramadol is
contraindicated or requires extreme caution in CYP2D6 UMs and PMs; alternative analgesics
(e.g., morphine, which does not require CYP2D6 activation) are preferred.
NGR 6172 — Advanced Pharmacology
& Pharmacotherapeutics Practice
Examination 2026/2027.
DOMAIN 1: Pharmacokinetics, Pharmacodynamics & Drug Interactions
(14 Questions)
Question 1 (Multiple-Choice)
A 62-year-old male with coronary artery disease is prescribed clopidogrel 75 mg daily following
drug-eluting stent placement. The patient is also prescribed omeprazole 20 mg daily for GERD.
Genetic testing reveals the patient is a CYP2C19 *2/*2 poor metabolizer.
Which of the following best describes the clinical consequence of this pharmacogenomic
finding?
A) The patient will have excessive active metabolite formation, increasing bleeding risk. B) The
patient requires reduced clopidogrel dosing due to enhanced first-pass metabolism. C) The
patient is at increased risk of stent thrombosis due to inadequate bioactivation of clopidogrel.
D) The patient should switch to omeprazole 40 mg daily to enhance CYP2C19-mediated
conversion.
[CORRECT: C] Rationale: Clopidogrel is a prodrug that requires hepatic bioactivation by the
cytochrome P450 2C19 (CYP2C19) enzyme to form its active thiol metabolite, which irreversibly
inhibits the P2Y12 ADP receptor on platelets. A patient with a CYP2C19 *2/*2 loss-of-function
allele (poor metabolizer phenotype) cannot adequately convert clopidogrel to its active moiety,
resulting in diminished antiplatelet effect and a significantly increased risk of recurrent coronary
stent thrombosis. The concomitant omeprazole further inhibits CYP2C19, compounding the risk.
Evidence-based practice supports switching to prasugrel or ticagrelor in CYP2C19 poor
metabolizers.
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Question 2 (Multiple-Choice)
A patient with atrial fibrillation is prescribed amiodarone 400 mg daily. The patient also takes
simvastatin 80 mg daily for hyperlipidemia. The prescriber is concerned about an increased risk
of myopathy and rhabdomyolysis.
Which CYP450 enzyme is primarily responsible for this clinically significant drug-drug
interaction?
A) CYP1A2 B) CYP2D6 C) CYP3A4 D) CYP2C9
[CORRECT: C] Rationale: Simvastatin is a CYP3A4 substrate that undergoes extensive first-pass
hepatic metabolism. Amiodarone is a potent CYP3A4 inhibitor that reduces the hepatic
clearance of simvastatin, leading to increased systemic exposure, elevated serum simvastatin
acid levels, and a heightened risk of dose-dependent myopathy and rhabdomyolysis. The FDA
recommends limiting simvastatin to 20 mg daily when co-prescribed with amiodarone due to
this specific CYP3A4-mediated interaction.
Question 3 (SATA)
A 58-year-old patient with HIV is prescribed ritonavir-boosted darunavir. The patient also takes
the following medications. Which of the following medications are CYP3A4 substrates whose
serum concentrations would be significantly elevated by ritonavir, creating a risk for toxicity?
(Select all that apply)
A) Atorvastatin B) Warfarin C) Sildenafil D) Tacrolimus E) Metformin
[CORRECT: A, C, D] Rationale: Ritonavir is a potent CYP3A4 inhibitor used as a pharmacokinetic
booster in antiretroviral therapy. CYP3A4 substrates whose hepatic metabolism is significantly
inhibited by ritonavir include: Atorvastatin (increased risk of myopathy/rhabdomyolysis),
Sildenafil (increased risk of hypotension and priapism—dose must be reduced), and Tacrolimus
(increased risk of nephrotoxicity and neurotoxicity—requires close trough monitoring). Warfarin
is primarily a CYP2C9 substrate (with minor CYP3A4 involvement for the R-enantiomer).
Metformin is renally eliminated unchanged and does not undergo CYP450 metabolism.
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Question 4 (Calculation-Based)
A 70-year-old male (weight: 78 kg, height: 175 cm) is prescribed warfarin for atrial fibrillation.
His baseline INR is 1.0. After 5 days of warfarin 5 mg daily, his INR is 2.5. The therapeutic target
is INR 2.0–3.0. His weekly dose is currently 35 mg.
Using the linear dosing adjustment formula: New Weekly Dose = (Current Weekly Dose ×
Target INR) / Current INR
Calculate the new weekly warfarin dose and the new daily dose (rounded to the nearest 0.5
mg).
A) Weekly: 28 mg; Daily: 4 mg B) Weekly: 30.8 mg; Daily: 4.5 mg C) Weekly: 32 mg; Daily: 4.5 mg
D) Weekly: 35 mg; Daily: 5 mg (no change needed)
[CORRECT: A] Rationale: Formula: New Weekly Dose = (Current Weekly Dose × Target INR) /
Current INR
• Current Weekly Dose = 35 mg
• Target INR (midpoint) = 2.5
• Current INR = 2.5
Calculation: New Weekly Dose = (35 mg × 2.5) / 2.5 = 35 mg / 2.5 × 2.5 = 28 mg
However, since the patient is already at the therapeutic target (INR 2.5 falls within 2.0–3.0), the
prescriber may choose to maintain the current dose. But if targeting the lower bound (INR 2.0):
New Weekly Dose = (35 × 2.0) / 2.5 = 28 mg New Daily Dose = 28 mg / 7 = 4 mg
Warfarin has a narrow therapeutic index (TI ≈ 2–3), requiring precise INR monitoring and dose
titration to maintain therapeutic efficacy while minimizing bleeding risk.
Question 5 (Multiple-Choice)
A patient with community-acquired pneumonia is prescribed clarithromycin 500 mg BID. The
patient has a history of atrial fibrillation and takes fluconazole 200 mg daily for esophageal
candidiasis. The prescriber is concerned about QT prolongation.
Which statement accurately describes the mechanism of this drug-drug interaction?
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A) Fluconazole inhibits CYP2D6, reducing clarithromycin metabolism and increasing QT risk. B)
Fluconazole inhibits CYP3A4, reducing clarithromycin hepatic clearance and increasing the risk
of torsades de pointes. C) Clarithromycin inhibits fluconazole metabolism via CYP2C9, causing
additive cardiotoxicity. D) Both drugs are CYP3A4 inducers, causing increased active metabolite
formation and QT prolongation.
[CORRECT: B] Rationale: Clarithromycin is a CYP3A4 substrate that also inhibits the hERG
potassium channel (IKr), prolonging the QT interval. Fluconazole is a potent CYP3A4 inhibitor
that reduces the hepatic clearance of clarithromycin, leading to elevated serum clarithromycin
concentrations and an additive or synergistic risk of QT prolongation and torsades de pointes.
This is a classic example of a CYP3A4 inhibitor (fluconazole) increasing the systemic exposure
and cardiac toxicity of a CYP3A4 substrate (clarithromycin). Alternative macrolides with less QT
risk (azithromycin) or alternative antifungals should be considered.
Question 6 (Multiple-Choice)
A 45-year-old patient with chronic pain is prescribed tramadol 50 mg every 6 hours PRN.
Genetic testing reveals the patient is a CYP2D6 ultra-rapid metabolizer (UM).
What is the primary clinical concern with tramadol prescribing in this patient?
A) The patient will not convert tramadol to its active metabolite and will have inadequate
analgesia. B) The patient will rapidly convert tramadol to O-desmethyltramadol (M1), increasing
the risk of opioid toxicity and respiratory depression. C) The patient requires a prodrug activator
to enhance CYP2D6 function. D) The patient should receive tramadol ER to bypass first-pass
metabolism.
[CORRECT: B] Rationale: Tramadol is a prodrug that requires CYP2D6-mediated O-
demethylation to form its active metabolite, O-desmethyltramadol (M1), which has
approximately 200-fold greater mu-opioid receptor affinity than the parent drug. A CYP2D6
ultra-rapid metabolizer (UM) genotype (e.g., *1×N/*1×N) results in excessively rapid and
complete bioactivation, leading to supratherapeutic M1 concentrations, increased opioid
toxicity (respiratory depression, sedation, seizures), and potential fatality. Tramadol is
contraindicated or requires extreme caution in CYP2D6 UMs and PMs; alternative analgesics
(e.g., morphine, which does not require CYP2D6 activation) are preferred.
