Pharmacology Pharmacokinetic Principles 2 — Questions and Answers
Question 1: A drug with a large volume of distribution (Vd) is most likely doing which of the following?
- Remaining primarily in the plasma
- Extensively distributed into peripheral tissues (Correct answer)
- Undergoing rapid renal elimination
- Binding exclusively to albumin
Correct answer: Extensively distributed into peripheral tissues
A large Vd indicates the drug is widely distributed into tissues beyond the plasma compartment.
Question 2: Which of the following best defines bioavailability?
- The rate at which a drug is eliminated from the body
- The fraction of administered drug that reaches systemic circulation unchanged (Correct answer)
- The ability of a drug to cross the blood-brain barrier
- The percentage of drug bound to plasma proteins
Correct answer: The fraction of administered drug that reaches systemic circulation unchanged
Bioavailability (F) is the fraction of an administered dose that reaches systemic circulation in active form.
Question 3: A drug undergoes significant first-pass metabolism. Which route of administration would BEST avoid this effect?
- Oral
- Sublingual
- Rectal (distal portion)
- Intramuscular (Correct answer)
Correct answer: Intramuscular
Intramuscular injection delivers drug directly into systemic circulation, bypassing hepatic first-pass metabolism entirely.
Question 4: What is the clinical significance of a drug with a high extraction ratio?
- It is minimally affected by changes in liver blood flow
- Its clearance is highly sensitive to changes in liver blood flow (Correct answer)
- It has a long half-life
- It requires renal dose adjustment only
Correct answer: Its clearance is highly sensitive to changes in liver blood flow
High extraction ratio drugs (>0.7) have flow-limited clearance, meaning hepatic blood flow changes significantly affect drug elimination.
Question 5: A patient has chronic kidney disease with a GFR of 20 mL/min. Which pharmacokinetic parameter is most directly affected?
- Volume of distribution
- Protein binding
- Renal clearance (Correct answer)
- First-pass metabolism
Correct answer: Renal clearance
Renal clearance is directly reduced in CKD as glomerular filtration rate declines, prolonging drug half-life.
Question 6: Which of the following is the correct formula for calculating drug half-life (t½)?
- t½ = Vd × CL
- t½ = 0.693 × Vd / CL (Correct answer)
- t½ = CL / Vd
- t½ = 0.693 / Vd × dose
Correct answer: t½ = 0.693 × Vd / CL
Half-life is calculated as 0.693 multiplied by volume of distribution divided by clearance.
Question 7: After how many half-lives does a drug reach approximately 97% of steady-state concentration?
- 2
- 3
- 5 (Correct answer)
- 7
Correct answer: 5
After 5 half-lives, a drug reaches approximately 97% of its steady-state concentration during continuous dosing.
Pharmacology Pharmacokinetic Principles 2
A drug with a large volume of distribution (Vd) is most likely doing which of the following?