OSCE Pharmacology Fundamentals 2 — Questions and Answers
Question 1: A patient is prescribed warfarin. Which enzyme system is primarily responsible for its metabolism?
- CYP2C9 (Correct answer)
- CYP3A4
- CYP1A2
- CYP2D6
Correct answer: CYP2C9
Warfarin is primarily metabolized by CYP2C9, making it susceptible to interactions with CYP2C9 inhibitors or inducers.
Question 2: A drug has a therapeutic index of 2. Which statement best describes this drug?
- It has a narrow safety margin between therapeutic and toxic doses (Correct answer)
- It is twice as potent as a reference drug
- It requires twice the dose to produce an effect
- It is suitable for self-administration without monitoring
Correct answer: It has a narrow safety margin between therapeutic and toxic doses
A therapeutic index of 2 means the toxic dose is only twice the effective dose, indicating a narrow safety margin requiring close monitoring.
Question 3: Which pharmacokinetic parameter describes the fraction of an administered dose that reaches systemic circulation unchanged?
- Bioavailability (Correct answer)
- Volume of distribution
- Clearance
- Half-life
Correct answer: Bioavailability
Bioavailability (F) is the fraction of administered drug that reaches systemic circulation in its active form.
Question 4: A patient taking phenytoin starts rifampicin. The nurse should anticipate which change?
- Reduced phenytoin levels due to enzyme induction (Correct answer)
- Increased phenytoin levels due to enzyme inhibition
- No change because phenytoin is renally cleared
- Increased rifampicin toxicity due to competition
Correct answer: Reduced phenytoin levels due to enzyme induction
Rifampicin is a potent CYP enzyme inducer that accelerates phenytoin metabolism, lowering its plasma levels.
Question 5: Which receptor type uses a G-protein coupled mechanism to mediate its intracellular effects?
- Beta-adrenergic receptor (Correct answer)
- Nicotinic acetylcholine receptor
- Insulin receptor
- Androgen receptor
Correct answer: Beta-adrenergic receptor
Beta-adrenergic receptors couple to Gs proteins, activating adenylyl cyclase and increasing intracellular cAMP.
Question 6: A drug is described as having zero-order kinetics. What does this mean clinically?
- A constant amount of drug is eliminated per unit time regardless of concentration (Correct answer)
- The drug is eliminated proportionally to its plasma concentration
- The drug has no measurable half-life
- Elimination doubles when the dose is doubled
Correct answer: A constant amount of drug is eliminated per unit time regardless of concentration
Zero-order kinetics means saturable elimination mechanisms are overwhelmed, so a fixed amount (not a fixed fraction) is removed per unit time.
Question 7: Which route of drug administration completely bypasses first-pass hepatic metabolism?
- Intravenous (Correct answer)
- Oral
- Rectal (upper rectum)
- Sublingual only
Correct answer: Intravenous
Intravenous administration delivers drug directly into systemic circulation, entirely bypassing hepatic first-pass metabolism.
OSCE Pharmacology Fundamentals 2
A patient is prescribed warfarin.
Which enzyme system is primarily responsible for its metabolism?