NR 546 FINAL EXAM
1. Approximately how long does it take a drug with a constant dosing
schedule to reach steady state?
A. Immediately after the first dose
B. About 10 half-lives
C. About 1 half-life
D. About 4 to 5 half-lives
Correct Answer: D. About 4 to 5 half-lives
Rationale: Steady state is reached after roughly 4 to 5 half-lives, when the amount
of drug absorbed equals the amount eliminated.
2. Why do many orally administered psychotropic drugs have reduced
bioavailability?
A. They bind irreversibly to albumin in the gut
B. They are never absorbed in the small intestine
C. First-pass hepatic metabolism removes part of the dose before it reaches
systemic circulation
D. They are excreted unchanged in bile only
Correct Answer: C. First-pass hepatic metabolism removes part of the dose
before it reaches systemic circulation
Rationale: Drugs absorbed from the gut pass through the portal circulation and liver
first, where extensive metabolism can lower the amount reaching the systemic
circulation.
NR 546 Final Exam | Page 1
,3. Which cytochrome P450 enzyme metabolizes the largest number of
medications?
A. CYP2D6
B. CYP3A4
C. CYP2C9
D. CYP1A2
Correct Answer: B. CYP3A4
Rationale: CYP3A4 is the most abundant hepatic and intestinal CYP enzyme and
metabolizes roughly half of all drugs.
4. A patient taking a strong CYP2D6 inhibitor such as fluoxetine or paroxetine
is prescribed nortriptyline. What is the expected effect?
A. Decreased nortriptyline levels and loss of efficacy
B. Rapid conversion to an inactive metabolite
C. Increased nortriptyline plasma levels and greater risk of toxicity
D. No change because nortriptyline is renally cleared
Correct Answer: C. Increased nortriptyline plasma levels and greater risk of
toxicity
Rationale: Inhibiting CYP2D6 slows TCA metabolism, raising plasma
concentrations and the risk of anticholinergic and cardiac toxicity.
5. A woman taking an oral contraceptive is started on carbamazepine. What is
the most important counseling point?
A. Carbamazepine induces CYP3A4 and can lower contraceptive hormone
levels, reducing effectiveness
B. Carbamazepine increases contraceptive levels and causes clotting
C. Carbamazepine causes the contraceptive to be excreted more slowly
D. Carbamazepine has no interaction with hormonal contraceptives
Correct Answer: A. Carbamazepine induces CYP3A4 and can lower
contraceptive hormone levels, reducing effectiveness
Rationale: Carbamazepine is a potent enzyme inducer that speeds hormone
metabolism, so a backup or non-hormonal method is needed.
NR 546 Final Exam | Page 2
,6. Which food or beverage can raise plasma levels of CYP3A4 substrates such
as buspirone or quetiapine?
A. Green tea
B. Cranberry juice
C. Whole milk
D. Grapefruit juice
Correct Answer: D. Grapefruit juice
Rationale: Grapefruit juice inhibits intestinal CYP3A4, reducing first-pass
metabolism and increasing drug levels.
7. Valproate is added to a patient who is stable on warfarin. Why is this a
concern?
A. Valproate is converted to warfarin in the liver
B. Valproate induces warfarin metabolism and causes clotting
C. Valproate is highly protein bound and can displace warfarin, raising the free
fraction and bleeding risk
D. Valproate blocks warfarin absorption
Correct Answer: C. Valproate is highly protein bound and can displace
warfarin, raising the free fraction and bleeding risk
Rationale: Displacement from albumin increases free drug concentration of highly
protein-bound agents, and valproate can also impair platelet function.
8. A CYP2D6 poor metabolizer is prescribed a standard dose of a tricyclic
antidepressant. What is the greatest concern?
A. Increased renal clearance
B. Immediate hypersensitivity reaction
C. Elevated drug levels with toxicity
D. Subtherapeutic levels
Correct Answer: C. Elevated drug levels with toxicity
Rationale: Poor metabolizers clear CYP2D6 substrates slowly, so standard doses
can produce toxic concentrations.
NR 546 Final Exam | Page 3
, 9. A patient who smokes cigarettes is stable on clozapine and then quits
smoking. What is the expected effect?
A. Clozapine levels are unchanged
B. Clozapine is converted to a more toxic metabolite
C. Clozapine levels rise because CYP1A2 induction is lost
D. Clozapine levels fall because of decreased absorption
Correct Answer: C. Clozapine levels rise because CYP1A2 induction is lost
Rationale: Tobacco smoke induces CYP1A2. After cessation, induction fades and
clozapine (and olanzapine) levels can rise significantly, so dose reduction and
monitoring may be needed.
10. Why does lithium require serum level monitoring?
A. It has a narrow therapeutic index
B. It is metabolized by CYP2D6
C. It has a very short duration of action of minutes
D. It is a prodrug requiring activation
Correct Answer: A. It has a narrow therapeutic index
Rationale: The margin between therapeutic and toxic concentrations of lithium is
small, so levels must be monitored.
11. Which is the primary mechanism of action of SSRIs?
A. Enhancing GABA-A receptor chloride flux
B. Blocking the serotonin transporter to increase synaptic serotonin
C. Inhibiting monoamine oxidase A and B
D. Blocking postsynaptic dopamine D2 receptors
Correct Answer: B. Blocking the serotonin transporter to increase synaptic
serotonin
Rationale: SSRIs selectively inhibit the presynaptic serotonin reuptake transporter
(SERT), increasing serotonin availability in the synapse.
NR 546 Final Exam | Page 4
1. Approximately how long does it take a drug with a constant dosing
schedule to reach steady state?
A. Immediately after the first dose
B. About 10 half-lives
C. About 1 half-life
D. About 4 to 5 half-lives
Correct Answer: D. About 4 to 5 half-lives
Rationale: Steady state is reached after roughly 4 to 5 half-lives, when the amount
of drug absorbed equals the amount eliminated.
2. Why do many orally administered psychotropic drugs have reduced
bioavailability?
A. They bind irreversibly to albumin in the gut
B. They are never absorbed in the small intestine
C. First-pass hepatic metabolism removes part of the dose before it reaches
systemic circulation
D. They are excreted unchanged in bile only
Correct Answer: C. First-pass hepatic metabolism removes part of the dose
before it reaches systemic circulation
Rationale: Drugs absorbed from the gut pass through the portal circulation and liver
first, where extensive metabolism can lower the amount reaching the systemic
circulation.
NR 546 Final Exam | Page 1
,3. Which cytochrome P450 enzyme metabolizes the largest number of
medications?
A. CYP2D6
B. CYP3A4
C. CYP2C9
D. CYP1A2
Correct Answer: B. CYP3A4
Rationale: CYP3A4 is the most abundant hepatic and intestinal CYP enzyme and
metabolizes roughly half of all drugs.
4. A patient taking a strong CYP2D6 inhibitor such as fluoxetine or paroxetine
is prescribed nortriptyline. What is the expected effect?
A. Decreased nortriptyline levels and loss of efficacy
B. Rapid conversion to an inactive metabolite
C. Increased nortriptyline plasma levels and greater risk of toxicity
D. No change because nortriptyline is renally cleared
Correct Answer: C. Increased nortriptyline plasma levels and greater risk of
toxicity
Rationale: Inhibiting CYP2D6 slows TCA metabolism, raising plasma
concentrations and the risk of anticholinergic and cardiac toxicity.
5. A woman taking an oral contraceptive is started on carbamazepine. What is
the most important counseling point?
A. Carbamazepine induces CYP3A4 and can lower contraceptive hormone
levels, reducing effectiveness
B. Carbamazepine increases contraceptive levels and causes clotting
C. Carbamazepine causes the contraceptive to be excreted more slowly
D. Carbamazepine has no interaction with hormonal contraceptives
Correct Answer: A. Carbamazepine induces CYP3A4 and can lower
contraceptive hormone levels, reducing effectiveness
Rationale: Carbamazepine is a potent enzyme inducer that speeds hormone
metabolism, so a backup or non-hormonal method is needed.
NR 546 Final Exam | Page 2
,6. Which food or beverage can raise plasma levels of CYP3A4 substrates such
as buspirone or quetiapine?
A. Green tea
B. Cranberry juice
C. Whole milk
D. Grapefruit juice
Correct Answer: D. Grapefruit juice
Rationale: Grapefruit juice inhibits intestinal CYP3A4, reducing first-pass
metabolism and increasing drug levels.
7. Valproate is added to a patient who is stable on warfarin. Why is this a
concern?
A. Valproate is converted to warfarin in the liver
B. Valproate induces warfarin metabolism and causes clotting
C. Valproate is highly protein bound and can displace warfarin, raising the free
fraction and bleeding risk
D. Valproate blocks warfarin absorption
Correct Answer: C. Valproate is highly protein bound and can displace
warfarin, raising the free fraction and bleeding risk
Rationale: Displacement from albumin increases free drug concentration of highly
protein-bound agents, and valproate can also impair platelet function.
8. A CYP2D6 poor metabolizer is prescribed a standard dose of a tricyclic
antidepressant. What is the greatest concern?
A. Increased renal clearance
B. Immediate hypersensitivity reaction
C. Elevated drug levels with toxicity
D. Subtherapeutic levels
Correct Answer: C. Elevated drug levels with toxicity
Rationale: Poor metabolizers clear CYP2D6 substrates slowly, so standard doses
can produce toxic concentrations.
NR 546 Final Exam | Page 3
, 9. A patient who smokes cigarettes is stable on clozapine and then quits
smoking. What is the expected effect?
A. Clozapine levels are unchanged
B. Clozapine is converted to a more toxic metabolite
C. Clozapine levels rise because CYP1A2 induction is lost
D. Clozapine levels fall because of decreased absorption
Correct Answer: C. Clozapine levels rise because CYP1A2 induction is lost
Rationale: Tobacco smoke induces CYP1A2. After cessation, induction fades and
clozapine (and olanzapine) levels can rise significantly, so dose reduction and
monitoring may be needed.
10. Why does lithium require serum level monitoring?
A. It has a narrow therapeutic index
B. It is metabolized by CYP2D6
C. It has a very short duration of action of minutes
D. It is a prodrug requiring activation
Correct Answer: A. It has a narrow therapeutic index
Rationale: The margin between therapeutic and toxic concentrations of lithium is
small, so levels must be monitored.
11. Which is the primary mechanism of action of SSRIs?
A. Enhancing GABA-A receptor chloride flux
B. Blocking the serotonin transporter to increase synaptic serotonin
C. Inhibiting monoamine oxidase A and B
D. Blocking postsynaptic dopamine D2 receptors
Correct Answer: B. Blocking the serotonin transporter to increase synaptic
serotonin
Rationale: SSRIs selectively inhibit the presynaptic serotonin reuptake transporter
(SERT), increasing serotonin availability in the synapse.
NR 546 Final Exam | Page 4
