APC Pharmacology Fundamentals 3 — Questions and Answers
Question 1: At steady state, the rate of drug administration equals:
- The rate of absorption
- The volume of distribution divided by half-life
- The rate of drug elimination (Correct answer)
- The peak plasma concentration
Correct answer: The rate of drug elimination
Steady state is reached when the rate of drug input equals the rate of elimination, resulting in stable plasma concentrations over time.
Question 2: A drug that exhibits zero-order kinetics is eliminated at a rate that is:
- Proportional to the plasma drug concentration
- Constant regardless of the plasma drug concentration (Correct answer)
- Faster at low concentrations
- Dependent on renal clearance only
Correct answer: Constant regardless of the plasma drug concentration
Zero-order kinetics means a constant amount of drug is eliminated per unit time, independent of plasma concentration, because elimination pathways are saturated.
Question 3: Which route of administration completely bypasses first-pass hepatic metabolism?
- Oral
- Sublingual
- Rectal (lower rectum)
- Sublingual and intravenous (Correct answer)
Correct answer: Sublingual and intravenous
Both sublingual and intravenous routes bypass first-pass hepatic metabolism; sublingual via direct absorption into systemic veins, IV by direct entry into circulation.
Question 4: Tachyphylaxis refers to:
- Decreased drug effect after a single large dose
- Rapid development of tolerance upon repeated administration (Correct answer)
- Increased sensitivity to a drug over time
- Cross-tolerance between unrelated drugs
Correct answer: Rapid development of tolerance upon repeated administration
Tachyphylaxis is a rapid, short-term decrease in response to a drug following repeated administration, often due to receptor desensitisation or depletion of mediators.
Question 5: The loading dose of a drug is primarily determined by:
- Clearance and desired steady-state concentration
- Volume of distribution and desired target concentration (Correct answer)
- Bioavailability and half-life
- Protein binding and renal function
Correct answer: Volume of distribution and desired target concentration
The loading dose is calculated as Vd × target concentration, and is used to rapidly achieve therapeutic drug levels.
Question 6: Which of the following best describes a partial agonist?
- A drug with high affinity but zero intrinsic efficacy
- A drug that produces a submaximal response even when all receptors are occupied (Correct answer)
- A drug that acts at a different receptor subtype than the full agonist
- A drug that requires bioactivation to produce an effect
Correct answer: A drug that produces a submaximal response even when all receptors are occupied
A partial agonist has intrinsic efficacy but cannot produce the maximum response even at full receptor occupancy, unlike a full agonist.
Question 7: Enterohepatic recycling of a drug typically results in:
- Faster elimination of the drug
- Prolonged drug action due to reabsorption from the gut (Correct answer)
- Increased renal clearance
- Decreased volume of distribution
Correct answer: Prolonged drug action due to reabsorption from the gut
Enterohepatic recycling occurs when a drug excreted in bile is reabsorbed from the intestine, cycling back to the liver and prolonging its half-life and effects.
APC Pharmacology Fundamentals 3
At steady state, the rate of drug administration equals: