HERZING UNIVERSITY
Course Code: NU 636
Instructor:
Date: 2026
FINAL EXAM – ADVANCED PHARMACOLOGY
A 72-year-old male with chronic kidney disease (eGFR 28
mL/min/1.73m2), heart failure, and atrial fibrillation is prescribed
digoxin 0.25 mg daily. Three days later he presents with nausea,
vomiting, visual disturbances (yellow-green halos), and bradycardia
(HR 42). His serum digoxin level is 3.1 ng/mL. Which pharmacokinetic
principle best explains why this patient developed digoxin toxicity at a
standard dose?
A) Increased first-pass metabolism due to reduced hepatic blood flow in
heart failure B) Reduced renal clearance secondary to CKD, leading to drug
accumulation and a narrowed therapeutic index C) Increased volume of
distribution due to fluid overload causing supratherapeutic peak levels D)
Enzyme induction by a co-administered medication reducing digoxin protein
binding
Correct Answer: B
Rationale: Digoxin is primarily eliminated by the kidneys (70 to 80% renal
excretion unchanged). In a patient with an eGFR of 28 mL/min, renal
clearance is severely diminished, causing digoxin to accumulate with
repeated dosing. Digoxin has a very narrow therapeutic index (0.5 to 2.0
ng/mL for heart failure, higher for rate control), meaning small increases in
drug concentration can produce toxicity. The appropriate dose adjustment for
this patient would be a reduced daily dose (0.0625 to 0.125 mg) or extending
the dosing interval. Fluid overload actually increases the volume of
distribution of digoxin (distributes into lean tissue), which could lower serum
levels, not raise them. Digoxin is minimally protein-bound (~25%) and
undergoes minimal hepatic metabolism. Treatment of digoxin toxicity
includes holding the drug, correcting electrolyte abnormalities (hypokalemia
1
,potentiates toxicity), and administering Digibind (digoxin-specific antibody
fragments) for severe cases.
A 55-year-old female with epilepsy is well-controlled on phenytoin 300
mg/day. She is newly diagnosed with tuberculosis and started on
rifampin. Four weeks later, she presents with breakthrough seizures.
Her phenytoin level is now 4.2 mcg/mL (previously therapeutic at 14
mcg/mL). What pharmacokinetic mechanism best explains this drug
interaction?
A) Rifampin is a potent inducer of CYP2C9 and CYP2C19, increasing
phenytoin metabolism and reducing its plasma concentration B) Rifampin
competes with phenytoin for albumin binding sites, increasing phenytoin's
free fraction and renal excretion C) Rifampin inhibits intestinal P-glycoprotein,
reducing phenytoin absorption in the small intestine D) Rifampin alkalinizes
urine, increasing ionization of phenytoin and promoting its tubular secretion
Correct Answer: A
Rationale: Rifampin is one of the most potent cytochrome P450 enzyme
inducers known, primarily inducing CYP3A4, CYP2C9, CYP2C19, CYP2C8,
and P-glycoprotein. Phenytoin is metabolized predominantly by CYP2C9 and
CYP2C19. Induction of these enzymes increases phenytoin's rate of hepatic
metabolism, reducing its half-life and plasma concentration significantly.
Enzyme induction is not immediate; it typically develops over 7 to 14 days as
new enzyme protein is synthesized, explaining the delayed onset of the
interaction. When rifampin is discontinued, enzyme activity returns to
baseline over a similar timeframe, potentially causing phenytoin toxicity if
doses were increased during the induction period. This is a clinically critical
interaction. Phenytoin dose escalation under close serum level monitoring is
required for the duration of rifampin therapy.
A 68-year-old male with severe liver cirrhosis (Child-Pugh Class C) is
prescribed morphine 10 mg orally every 4 hours for chronic cancer
pain. He develops profound sedation, respiratory depression, and
pinpoint pupils within 2 hours of his first dose. Which pharmacokinetic
alteration most directly explains this severe adverse effect?
A) Increased renal clearance of morphine metabolites due to compensatory
hyperfiltration B) Dramatically reduced hepatic first-pass metabolism,
resulting in significantly higher bioavailability and plasma morphine
concentration than expected C) Reduced protein binding of morphine to
albumin, increasing free drug fraction D) Increased blood-brain barrier
permeability due to hepatic encephalopathy allowing greater CNS
penetration
Correct Answer: B
Rationale: Morphine undergoes extensive hepatic first-pass metabolism
2
,(glucuronidation primarily, with some CYP3A4 involvement) when
administered orally, with normal bioavailability of approximately 30 to 40%. In
severe hepatic cirrhosis, first-pass extraction is dramatically reduced due to
hepatocyte loss and portosystemic shunting, which allows a much larger
proportion of the absorbed oral dose to reach systemic circulation intact. This
effectively means the patient receives the pharmacologic equivalent of a
much higher dose than intended, producing toxicity. Additionally, the active
metabolite morphine-6-glucuronide (M6G) accumulates in patients with
impaired hepatic and renal function, further contributing to CNS and
respiratory depression. In patients with severe cirrhosis, opioid doses should
begin at 25 to 50% of the standard dose with extended dosing intervals, and
close monitoring for CNS depression is mandatory.
A 45-year-old woman with bipolar disorder is stabilized on lithium 900
mg/day (serum level 0.9 mEq/L). She is prescribed ibuprofen 600 mg
three times daily for knee pain. Ten days later, she presents with coarse
tremor, confusion, ataxia, and a serum lithium level of 2.4 mEq/L. Which
mechanism explains this drug interaction?
A) Ibuprofen inhibits CYP3A4, reducing hepatic lithium metabolism and
increasing its half-life B) NSAIDs reduce renal prostaglandin synthesis,
decreasing renal blood flow and glomerular filtration rate, reducing lithium
clearance and causing toxicity C) Ibuprofen alkalinizes urine, reducing lithium
tubular secretion and increasing reabsorption D) NSAIDs displace lithium
from plasma protein binding sites, increasing the free fraction available for
renal filtration
Correct Answer: B
Rationale: Lithium is almost entirely cleared by the kidneys, filtered freely at
the glomerulus and reabsorbed by proximal tubular sodium transporters
(lithium is handled similarly to sodium). NSAIDs inhibit cyclooxygenase
(COX-1 and COX-2), reducing prostaglandin synthesis. Renal prostaglandins
play a critical role in maintaining afferent arteriolar vasodilation and
glomerular filtration rate, particularly under conditions of reduced renal
perfusion. NSAID-mediated prostaglandin inhibition causes afferent arteriolar
vasoconstriction, reducing GFR and consequently reducing lithium
clearance. As lithium accumulates, its narrow therapeutic index (0.6 to 1.2
mEq/L for maintenance) is exceeded, and toxicity develops rapidly. Lithium is
not protein-bound and undergoes no hepatic metabolism. Patients on lithium
should avoid NSAIDs; acetaminophen is the preferred analgesic alternative.
Thiazide diuretics cause a similar interaction via sodium depletion stimulating
proximal tubular sodium and lithium reabsorption.
A 34-year-old male with schizophrenia is started on clozapine. After 6
weeks of stable therapy, he begins smoking one pack of cigarettes per
3
, day after previously being a non-smoker. His psychiatric symptoms
worsen significantly. Which pharmacokinetic mechanism explains this
clinical deterioration?
A) Nicotine directly inhibits dopamine D2 receptors, antagonizing clozapine's
antipsychotic mechanism B) Polycyclic aromatic hydrocarbons (PAHs) in
cigarette smoke induce CYP1A2, accelerating clozapine metabolism and
significantly reducing plasma clozapine levels C) Nicotine acts as a CYP3A4
inhibitor, reducing clozapine conversion to its active norclozapine metabolite
D) Carbon monoxide in cigarette smoke increases plasma protein binding of
clozapine, reducing its free fraction
Correct Answer: B
Rationale: Clozapine is primarily metabolized by CYP1A2 (approximately
70%) with minor contributions from CYP3A4 and CYP2D6. Polycyclic
aromatic hydrocarbons (PAHs), not nicotine itself, found in cigarette smoke
are potent CYP1A2 inducers. Induction of CYP1A2 significantly increases
clozapine metabolism, reducing plasma clozapine levels by 40 to 50% in
heavy smokers compared to non-smokers. This is a critical pharmacokinetic
interaction with major clinical implications. Conversely, smoking cessation in
a patient stabilized on clozapine while smoking can cause a 50% or greater
rise in clozapine plasma levels, risking seizures, sedation, and metabolic
complications. Nicotine replacement therapy (patches, gum) does not contain
PAHs and does not affect CYP1A2. Clinicians must monitor clozapine levels
and adjust doses around smoking status changes.
A 62-year-old male with a deep vein thrombosis is initiated on warfarin.
Genetic testing reveals he is a CYP2C9 1/3 and VKORC1 AA genotype.
Compared to a patient with CYP2C9 1/1 and VKORC1 GG genotype, what
dose adjustment and clinical implication is expected?
A) This patient will require a higher warfarin dose because CYP2C9 3 is an
ultra-rapid metabolizer allele and VKORC1 AA increases warfarin resistance
B) This patient will require a significantly lower warfarin dose; CYP2C9 3
reduces S-warfarin metabolism and VKORC1 AA increases sensitivity to
warfarin's anticoagulant effect at any given dose C) No dose adjustment is
needed; pharmacogenomics does not reliably predict warfarin requirements
D) This patient should be switched to heparin as genotype-guided warfarin
dosing is not yet clinically applicable
Correct Answer: B
Rationale: Warfarin dosing is profoundly influenced by two genes. CYP2C9
encodes the primary enzyme responsible for metabolizing the more potent S-
warfarin enantiomer. The 3 allele is a loss-of-function variant that reduces
CYP2C9 enzymatic activity by approximately 90%, causing S-warfarin to
accumulate. VKORC1 encodes vitamin K epoxide reductase, warfarin's
molecular target. The VKORC1 AA genotype represents the -1639G>A
4
Course Code: NU 636
Instructor:
Date: 2026
FINAL EXAM – ADVANCED PHARMACOLOGY
A 72-year-old male with chronic kidney disease (eGFR 28
mL/min/1.73m2), heart failure, and atrial fibrillation is prescribed
digoxin 0.25 mg daily. Three days later he presents with nausea,
vomiting, visual disturbances (yellow-green halos), and bradycardia
(HR 42). His serum digoxin level is 3.1 ng/mL. Which pharmacokinetic
principle best explains why this patient developed digoxin toxicity at a
standard dose?
A) Increased first-pass metabolism due to reduced hepatic blood flow in
heart failure B) Reduced renal clearance secondary to CKD, leading to drug
accumulation and a narrowed therapeutic index C) Increased volume of
distribution due to fluid overload causing supratherapeutic peak levels D)
Enzyme induction by a co-administered medication reducing digoxin protein
binding
Correct Answer: B
Rationale: Digoxin is primarily eliminated by the kidneys (70 to 80% renal
excretion unchanged). In a patient with an eGFR of 28 mL/min, renal
clearance is severely diminished, causing digoxin to accumulate with
repeated dosing. Digoxin has a very narrow therapeutic index (0.5 to 2.0
ng/mL for heart failure, higher for rate control), meaning small increases in
drug concentration can produce toxicity. The appropriate dose adjustment for
this patient would be a reduced daily dose (0.0625 to 0.125 mg) or extending
the dosing interval. Fluid overload actually increases the volume of
distribution of digoxin (distributes into lean tissue), which could lower serum
levels, not raise them. Digoxin is minimally protein-bound (~25%) and
undergoes minimal hepatic metabolism. Treatment of digoxin toxicity
includes holding the drug, correcting electrolyte abnormalities (hypokalemia
1
,potentiates toxicity), and administering Digibind (digoxin-specific antibody
fragments) for severe cases.
A 55-year-old female with epilepsy is well-controlled on phenytoin 300
mg/day. She is newly diagnosed with tuberculosis and started on
rifampin. Four weeks later, she presents with breakthrough seizures.
Her phenytoin level is now 4.2 mcg/mL (previously therapeutic at 14
mcg/mL). What pharmacokinetic mechanism best explains this drug
interaction?
A) Rifampin is a potent inducer of CYP2C9 and CYP2C19, increasing
phenytoin metabolism and reducing its plasma concentration B) Rifampin
competes with phenytoin for albumin binding sites, increasing phenytoin's
free fraction and renal excretion C) Rifampin inhibits intestinal P-glycoprotein,
reducing phenytoin absorption in the small intestine D) Rifampin alkalinizes
urine, increasing ionization of phenytoin and promoting its tubular secretion
Correct Answer: A
Rationale: Rifampin is one of the most potent cytochrome P450 enzyme
inducers known, primarily inducing CYP3A4, CYP2C9, CYP2C19, CYP2C8,
and P-glycoprotein. Phenytoin is metabolized predominantly by CYP2C9 and
CYP2C19. Induction of these enzymes increases phenytoin's rate of hepatic
metabolism, reducing its half-life and plasma concentration significantly.
Enzyme induction is not immediate; it typically develops over 7 to 14 days as
new enzyme protein is synthesized, explaining the delayed onset of the
interaction. When rifampin is discontinued, enzyme activity returns to
baseline over a similar timeframe, potentially causing phenytoin toxicity if
doses were increased during the induction period. This is a clinically critical
interaction. Phenytoin dose escalation under close serum level monitoring is
required for the duration of rifampin therapy.
A 68-year-old male with severe liver cirrhosis (Child-Pugh Class C) is
prescribed morphine 10 mg orally every 4 hours for chronic cancer
pain. He develops profound sedation, respiratory depression, and
pinpoint pupils within 2 hours of his first dose. Which pharmacokinetic
alteration most directly explains this severe adverse effect?
A) Increased renal clearance of morphine metabolites due to compensatory
hyperfiltration B) Dramatically reduced hepatic first-pass metabolism,
resulting in significantly higher bioavailability and plasma morphine
concentration than expected C) Reduced protein binding of morphine to
albumin, increasing free drug fraction D) Increased blood-brain barrier
permeability due to hepatic encephalopathy allowing greater CNS
penetration
Correct Answer: B
Rationale: Morphine undergoes extensive hepatic first-pass metabolism
2
,(glucuronidation primarily, with some CYP3A4 involvement) when
administered orally, with normal bioavailability of approximately 30 to 40%. In
severe hepatic cirrhosis, first-pass extraction is dramatically reduced due to
hepatocyte loss and portosystemic shunting, which allows a much larger
proportion of the absorbed oral dose to reach systemic circulation intact. This
effectively means the patient receives the pharmacologic equivalent of a
much higher dose than intended, producing toxicity. Additionally, the active
metabolite morphine-6-glucuronide (M6G) accumulates in patients with
impaired hepatic and renal function, further contributing to CNS and
respiratory depression. In patients with severe cirrhosis, opioid doses should
begin at 25 to 50% of the standard dose with extended dosing intervals, and
close monitoring for CNS depression is mandatory.
A 45-year-old woman with bipolar disorder is stabilized on lithium 900
mg/day (serum level 0.9 mEq/L). She is prescribed ibuprofen 600 mg
three times daily for knee pain. Ten days later, she presents with coarse
tremor, confusion, ataxia, and a serum lithium level of 2.4 mEq/L. Which
mechanism explains this drug interaction?
A) Ibuprofen inhibits CYP3A4, reducing hepatic lithium metabolism and
increasing its half-life B) NSAIDs reduce renal prostaglandin synthesis,
decreasing renal blood flow and glomerular filtration rate, reducing lithium
clearance and causing toxicity C) Ibuprofen alkalinizes urine, reducing lithium
tubular secretion and increasing reabsorption D) NSAIDs displace lithium
from plasma protein binding sites, increasing the free fraction available for
renal filtration
Correct Answer: B
Rationale: Lithium is almost entirely cleared by the kidneys, filtered freely at
the glomerulus and reabsorbed by proximal tubular sodium transporters
(lithium is handled similarly to sodium). NSAIDs inhibit cyclooxygenase
(COX-1 and COX-2), reducing prostaglandin synthesis. Renal prostaglandins
play a critical role in maintaining afferent arteriolar vasodilation and
glomerular filtration rate, particularly under conditions of reduced renal
perfusion. NSAID-mediated prostaglandin inhibition causes afferent arteriolar
vasoconstriction, reducing GFR and consequently reducing lithium
clearance. As lithium accumulates, its narrow therapeutic index (0.6 to 1.2
mEq/L for maintenance) is exceeded, and toxicity develops rapidly. Lithium is
not protein-bound and undergoes no hepatic metabolism. Patients on lithium
should avoid NSAIDs; acetaminophen is the preferred analgesic alternative.
Thiazide diuretics cause a similar interaction via sodium depletion stimulating
proximal tubular sodium and lithium reabsorption.
A 34-year-old male with schizophrenia is started on clozapine. After 6
weeks of stable therapy, he begins smoking one pack of cigarettes per
3
, day after previously being a non-smoker. His psychiatric symptoms
worsen significantly. Which pharmacokinetic mechanism explains this
clinical deterioration?
A) Nicotine directly inhibits dopamine D2 receptors, antagonizing clozapine's
antipsychotic mechanism B) Polycyclic aromatic hydrocarbons (PAHs) in
cigarette smoke induce CYP1A2, accelerating clozapine metabolism and
significantly reducing plasma clozapine levels C) Nicotine acts as a CYP3A4
inhibitor, reducing clozapine conversion to its active norclozapine metabolite
D) Carbon monoxide in cigarette smoke increases plasma protein binding of
clozapine, reducing its free fraction
Correct Answer: B
Rationale: Clozapine is primarily metabolized by CYP1A2 (approximately
70%) with minor contributions from CYP3A4 and CYP2D6. Polycyclic
aromatic hydrocarbons (PAHs), not nicotine itself, found in cigarette smoke
are potent CYP1A2 inducers. Induction of CYP1A2 significantly increases
clozapine metabolism, reducing plasma clozapine levels by 40 to 50% in
heavy smokers compared to non-smokers. This is a critical pharmacokinetic
interaction with major clinical implications. Conversely, smoking cessation in
a patient stabilized on clozapine while smoking can cause a 50% or greater
rise in clozapine plasma levels, risking seizures, sedation, and metabolic
complications. Nicotine replacement therapy (patches, gum) does not contain
PAHs and does not affect CYP1A2. Clinicians must monitor clozapine levels
and adjust doses around smoking status changes.
A 62-year-old male with a deep vein thrombosis is initiated on warfarin.
Genetic testing reveals he is a CYP2C9 1/3 and VKORC1 AA genotype.
Compared to a patient with CYP2C9 1/1 and VKORC1 GG genotype, what
dose adjustment and clinical implication is expected?
A) This patient will require a higher warfarin dose because CYP2C9 3 is an
ultra-rapid metabolizer allele and VKORC1 AA increases warfarin resistance
B) This patient will require a significantly lower warfarin dose; CYP2C9 3
reduces S-warfarin metabolism and VKORC1 AA increases sensitivity to
warfarin's anticoagulant effect at any given dose C) No dose adjustment is
needed; pharmacogenomics does not reliably predict warfarin requirements
D) This patient should be switched to heparin as genotype-guided warfarin
dosing is not yet clinically applicable
Correct Answer: B
Rationale: Warfarin dosing is profoundly influenced by two genes. CYP2C9
encodes the primary enzyme responsible for metabolizing the more potent S-
warfarin enantiomer. The 3 allele is a loss-of-function variant that reduces
CYP2C9 enzymatic activity by approximately 90%, causing S-warfarin to
accumulate. VKORC1 encodes vitamin K epoxide reductase, warfarin's
molecular target. The VKORC1 AA genotype represents the -1639G>A
4
