KAPS Pharmacology Fundamentals 2 — Questions and Answers
Question 1: Which pharmacokinetic parameter describes the fraction of an administered dose that reaches systemic circulation unchanged?
- Clearance
- Bioavailability (Correct answer)
- Volume of distribution
- Half-life
Correct answer: Bioavailability
Bioavailability (F) is the fraction of administered drug that reaches systemic circulation in unchanged form.
Question 2: A drug with a narrow therapeutic index requires more careful dosing because:
- It is absorbed slowly from the GI tract
- The toxic dose is close to the therapeutic dose (Correct answer)
- It has a long elimination half-life
- It undergoes extensive first-pass metabolism
Correct answer: The toxic dose is close to the therapeutic dose
A narrow therapeutic index means there is little difference between the minimum effective concentration and the minimum toxic concentration.
Question 3: Which type of drug-receptor interaction is characterized by a drug that binds to a receptor and produces a submaximal effect even at full receptor occupancy?
- Full agonist
- Competitive antagonist
- Partial agonist (Correct answer)
- Inverse agonist
Correct answer: Partial agonist
A partial agonist activates receptors but produces a lower maximal effect (Emax) than a full agonist, even at 100% receptor occupancy.
Question 4: First-pass metabolism most significantly affects drugs administered by which route?
- Intravenous
- Sublingual
- Oral (Correct answer)
- Intramuscular
Correct answer: Oral
Orally administered drugs pass through the portal circulation to the liver before reaching systemic circulation, where extensive first-pass metabolism can significantly reduce bioavailability.
Question 5: The ED50 of a drug refers to the dose that produces the desired effect in:
- 50% of the maximum possible response
- 50% of the test population (Correct answer)
- The lowest 50th percentile of doses tested
- 50% of receptor occupancy
Correct answer: 50% of the test population
ED50 is the effective dose that produces the desired therapeutic response in 50% of the population studied.
Question 6: Cytochrome P450 enzyme induction by a co-administered drug is most likely to result in:
- Increased plasma levels of the substrate drug
- Decreased metabolism of the substrate drug
- Reduced plasma levels of the substrate drug (Correct answer)
- Competitive inhibition at the receptor
Correct answer: Reduced plasma levels of the substrate drug
Enzyme induction increases the rate of metabolism of substrate drugs, leading to lower plasma concentrations and potentially reduced therapeutic effect.
Question 7: Which term describes the phenomenon where repeated drug administration leads to a diminished pharmacological response over time?
- Sensitization
- Tachyphylaxis (Correct answer)
- Synergism
- Idiosyncrasy
Correct answer: Tachyphylaxis
Tachyphylaxis is the rapid development of tolerance to a drug's effects following repeated administration in a short time period.
KAPS Pharmacology Fundamentals 2
Which pharmacokinetic parameter describes the fraction of an administered dose that reaches systemic circulation unchanged?