Free PMHNP board review · 10 practice questions
Pharmacokinetics vs. Pharmacodynamics Practice Questions
Apply clearance, interactions, half-life, protein binding, and receptor effects.
Independent educational practice, not official ANCC exam items. Not affiliated with or endorsed by ANCC. Not individual clinical advice; use current prescribing information, local protocols, and clinical judgment in practice.
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Question 1 of 10
A patient develops a higher medication concentration after kidney function declines, without a dose change. Which concept most directly explains the concentration change?
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Correct answer: C. Altered pharmacokinetics
Reduced elimination changes exposure, a pharmacokinetic issue.
Why the other answers are less appropriate
- D. Increased receptor efficacy: Efficacy describes the achievable response, not elimination.
- A. Increased drug potency: Potency does not explain a clearance-related concentration increase.
- B. A new receptor target: The scenario does not describe a change in receptor target.
Question 2 of 10
An active parent drug is mainly cleared by CYP3A4. A strong CYP3A4 inhibitor is added, with other factors unchanged. What change is most likely?
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Correct answer: A. Higher parent-drug exposure
Inhibiting a major metabolic pathway can increase exposure to an active substrate.
Why the other answers are less appropriate
- B. Lower parent-drug exposure from faster metabolism: Faster metabolism is more consistent with induction.
- C. No possible concentration change because the dose is unchanged: The same dose can produce different exposure when clearance changes.
- D. Immediate conversion of the drug into a receptor antagonist: Enzyme inhibition does not change the drug’s receptor classification.
Question 3 of 10
A stable patient takes an active drug cleared largely by an inducible CYP pathway. An inducer is started. Which monitoring concern is most appropriate as induction develops?
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Correct answer: D. Reduced drug exposure and possible loss of benefit
Induction can increase clearance and reduce active-drug exposure; its time course is not necessarily immediate.
Why the other answers are less appropriate
- A. Guaranteed toxicity from reduced metabolism: The expected direction for this active substrate is increased metabolism.
- B. An immediate maximal interaction after the first inducer dose: Enzyme induction generally develops over time.
- C. No need to reassess until the original prescription expires: Interaction monitoring should follow the anticipated pharmacology and clinical response.
Question 4 of 10
A hypothetical drug has first-order elimination, a 24-hour half-life, and stable clearance. Regular dosing begins without a loading dose. Approximately when will concentrations be close to steady state?
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Correct answer: B. After 4 to 5 days
Four to five half-lives is the usual approximation under these stated assumptions.
Why the other answers are less appropriate
- C. After 4 to 5 hours: This is much less than one half-life.
- D. Only after the patient reports remission: Clinical response and concentration steady state follow different processes.
- A. After exactly one dose, regardless of dosing interval: Repeated dosing generally accumulates before a repeating steady-state pattern develops.
Question 5 of 10
A single dose of a hypothetical drug follows first-order elimination with a 12-hour half-life. No further doses are taken. Approximately what fraction remains after 36 hours?
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Correct answer: B. One eighth
Three half-lives leave (1/2) cubed, or 12.5%, of the initial amount.
Why the other answers are less appropriate
- C. One half: One half remains after one half-life.
- D. One quarter: One quarter remains after two half-lives.
- A. None: Elimination does not reach zero after three half-lives.
Question 6 of 10
Two drugs achieve the same maximal effect in a defined receptor assay, but drug A requires a lower concentration. Which conclusion is justified?
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Correct answer: D. Drug A is more potent in that assay.
Potency compares the amount needed for an effect; equal maxima do not show greater efficacy.
Why the other answers are less appropriate
- A. Drug A necessarily has greater maximal efficacy.: The scenario explicitly states equal maximal effects.
- B. Drug A is necessarily safer for every patient.: Safety cannot be inferred from potency alone.
- C. Drug A must have a longer elimination half-life.: Half-life is a pharmacokinetic property not established here.
Question 7 of 10
A ligand binds a receptor but produces a smaller maximal response than a full agonist in the same experimental system, even at high occupancy. What is the best classification?
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Correct answer: A. Partial agonist
A partial agonist has lower intrinsic efficacy than the full agonist in the same system.
Why the other answers are less appropriate
- B. Full agonist: The observed lower maximum is inconsistent with full agonism in this comparison.
- C. Pure antagonist with no intrinsic activity: An antagonist lacks the agonist activity described.
- D. CYP enzyme inducer: Receptor response does not identify an enzyme-inducing property.
Question 8 of 10
A patient taking valproate has low albumin, sedation, and a total concentration within the laboratory’s reference range. What is the best interpretation?
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Correct answer: C. The total level may underrepresent active unbound exposure; assess clinically and consider a free level.
Changes in protein binding can make total concentration misleading.
Why the other answers are less appropriate
- D. A reference-range total level excludes medication toxicity.: A total concentration does not fully characterize free exposure or individual susceptibility.
- A. Low albumin proves the patient missed doses.: Albumin does not establish adherence.
- B. Only the protein-bound fraction can cause pharmacologic effects.: Unbound drug is the pharmacologically available fraction.
Question 9 of 10
A patient on lithium develops acute kidney injury during an intercurrent illness. Which pharmacokinetic feature makes this especially important?
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Correct answer: D. Lithium is primarily eliminated by the kidneys.
Reduced renal clearance can increase lithium exposure and toxicity risk, requiring prompt clinical reassessment.
Why the other answers are less appropriate
- A. Lithium is mainly cleared through CYP3A4.: CYP3A4 is not its principal clearance pathway.
- B. Lithium is extensively metabolized before excretion.: Lithium is not metabolized.
- C. Lithium’s elimination is independent of kidney function.: Kidney function is central to lithium clearance.
Question 10 of 10
A medication blocks histamine H1 receptors and causes drowsiness. Which part of this explanation is pharmacodynamic?
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Correct answer: A. Receptor blockade producing a clinical effect
Pharmacodynamics links drug action at its target with a response.
Why the other answers are less appropriate
- B. The fraction absorbed from the intestine: Absorption belongs to pharmacokinetics.
- C. The rate of renal elimination: Elimination belongs to pharmacokinetics.
- D. The time required for plasma concentration to fall by half: Elimination half-life describes concentration over time.
Turn missed questions into focused review
Identify the clue that supports the best answer, then explain why the closest alternative is less appropriate. Return to the linked article to revisit a missed concept. This short practice set does not predict certification performance.
Frequently asked questions
Does steady state mean the patient has reached full clinical benefit?
No. A repeating concentration pattern and a therapeutic response are different endpoints. Clinical effects may develop earlier or later.
Does a CYP inhibitor always increase a drug’s benefit?
No. Effects depend on the specific drug, active metabolites, dose, and patient. Prodrugs may behave differently, and increased exposure can increase harm.