ABCN Pharmacology Fundamentals 2 — Questions and Answers
Question 1: Which pharmacokinetic parameter describes the fraction of an administered drug that reaches systemic circulation unchanged?
- Volume of distribution
- Bioavailability (Correct answer)
- Clearance
- Half-life
Correct answer: Bioavailability
Bioavailability (F) represents the fraction of a dose that reaches systemic circulation in an unchanged, active form.
Question 2: A neuropsychologist consults on a patient experiencing bradykinesia and cogwheel rigidity after antipsychotic initiation. Which receptor mechanism best explains these extrapyramidal effects?
- 5-HT2A antagonism in the striatum
- D2 receptor blockade in the nigrostriatal pathway (Correct answer)
- Muscarinic receptor agonism
- Alpha-1 adrenergic blockade
Correct answer: D2 receptor blockade in the nigrostriatal pathway
Blockade of D2 receptors in the nigrostriatal dopamine pathway causes parkinsonian extrapyramidal symptoms.
Question 3: Which of the following best characterizes zero-order kinetics?
- Elimination rate is proportional to drug concentration
- A constant amount of drug is eliminated per unit time (Correct answer)
- Half-life decreases as dose increases
- The drug is metabolized faster at lower concentrations
Correct answer: A constant amount of drug is eliminated per unit time
Zero-order kinetics means a fixed amount (not a fixed percentage) of drug is eliminated per unit time, as seen with ethanol and phenytoin at toxic doses.
Question 4: A patient taking lithium develops polyuria and polydipsia. Which mechanism underlies this side effect?
- Lithium blocks aldosterone synthesis
- Lithium antagonizes ADH (vasopressin) action in the renal collecting duct (Correct answer)
- Lithium increases renal glucose excretion
- Lithium activates angiotensin II receptors
Correct answer: Lithium antagonizes ADH (vasopressin) action in the renal collecting duct
Lithium causes nephrogenic diabetes insipidus by interfering with ADH signaling in collecting duct cells.
Question 5: Carbamazepine's autoinduction of CYP3A4 results in which clinically significant observation?
- Increasing plasma levels over the first month of therapy
- Decreasing plasma levels over the first month requiring dose adjustment (Correct answer)
- No change in plasma levels due to stable protein binding
- Enhanced efficacy due to active metabolite accumulation
Correct answer: Decreasing plasma levels over the first month requiring dose adjustment
Carbamazepine induces its own metabolism via CYP3A4, causing plasma levels to fall over 2–4 weeks and necessitating dose increases.
Question 6: Which SSRI has the longest elimination half-life, making it least likely to cause discontinuation syndrome?
- Paroxetine
- Sertraline
- Fluoxetine (Correct answer)
- Escitalopram
Correct answer: Fluoxetine
Fluoxetine has a half-life of 1–4 days and its active metabolite norfluoxetine has a half-life of 4–16 days, providing a slow self-taper.
Question 7: In pharmacodynamics, what does the term 'efficacy' specifically refer to?
- The dose required to produce 50% of maximal effect
- The maximum response a drug can produce regardless of dose (Correct answer)
- The selectivity of a drug for its target receptor
- The rate at which a drug reaches its receptor
Correct answer: The maximum response a drug can produce regardless of dose
Efficacy (Emax) is the maximum pharmacological effect a drug can produce when all receptors are occupied.
ABCN Pharmacology Fundamentals 2
Which pharmacokinetic parameter describes the fraction of an administered drug that reaches systemic circulation unchanged?