Introduction to clinical pharmacokinetics: compartmental models MCQs With Answer

Introduction: This quiz set on Introduction to Clinical Pharmacokinetics: Compartmental Models is designed for M.Pharm students to strengthen conceptual understanding and application of compartmental pharmacokinetic theory. It covers one- and two‑compartment models, micro‑ and macro‑constants, distribution and elimination phases, clearance and volume concepts, infusion and bolus dosing, steady state, and model identifiability. Questions require recognition of equations, parameter relationships, and practical implications for therapeutic drug monitoring and dosage design. Use this set to test recall, integrate theory with data interpretation, and prepare for advanced problem solving in clinical pharmacokinetics.

Q1. Which statement best describes the assumption of a one‑compartment pharmacokinetic model?

• The entire body is represented as a single, well‑mixed compartment (instantaneous distribution)

Correct Answer: The entire body is represented as a single, well‑mixed compartment (instantaneous distribution)

Q2. For an IV bolus one‑compartment model with first‑order elimination, which equation describes the plasma concentration vs time?

• C = C0 e^-kt (first‑order elimination)

Correct Answer: C = C0 e^-kt (first‑order elimination)

Q3. Apparent volume of distribution (Vd) after an IV bolus is most directly calculated as which expression?

• Apparent volume calculated as Vd = Dose / C0

Correct Answer: Apparent volume calculated as Vd = Dose / C0

Q4. Which definition best describes systemic clearance (CL)?

• Volume of plasma cleared of drug per unit time (CL = Rate of elimination / plasma concentration)

Correct Answer: Volume of plasma cleared of drug per unit time (CL = Rate of elimination / plasma concentration)

Q5. In a two‑compartment IV bolus model, what do the fast (alpha) and slow (beta) phases represent?

• Alpha phase corresponds to rapid distribution; beta phase corresponds to slower elimination from the body

Correct Answer: Alpha phase corresponds to rapid distribution; beta phase corresponds to slower elimination from the body

Q6. In standard two‑compartment microconstants, what process does k21 represent?

• Transfer rate constant from peripheral compartment back to central compartment (peripheral → central)

Correct Answer: Transfer rate constant from peripheral compartment back to central compartment (peripheral → central)

Q7. How does a biexponential concentration–time profile differ from a monoexponential profile?

• Biexponential has two exponential terms reflecting distribution and elimination phases; monoexponential has one term

Correct Answer: Biexponential has two exponential terms reflecting distribution and elimination phases; monoexponential has one term

Q8. Approximately how long does it take to reach steady state during a constant rate infusion for a first‑order elimination process?

• Approximately 4–5 elimination half‑lives to reach >95% of steady state

Correct Answer: Approximately 4–5 elimination half‑lives to reach >95% of steady state

Q9. In the two‑compartment model after an IV bolus, the intercept C0 obtained by extrapolating the biexponential curve to time zero most closely reflects which concentration?

• Concentration in the central compartment immediately after bolus (not whole‑body apparent concentration)

Correct Answer: Concentration in the central compartment immediately after bolus (not whole‑body apparent concentration)

Q10. Which description correctly characterizes a “mammillary” multi‑compartment model?

• Central compartment connected to one or more peripheral compartments; peripheral compartments are not directly connected to each other

Correct Answer: Central compartment connected to one or more peripheral compartments; peripheral compartments are not directly connected to each other

Q11. The distribution half‑life (t1/2α) in a two‑compartment model is related to the alpha rate constant how?

• t1/2α = ln(2) / alpha
• t1/2α = alpha × ln(2)
• t1/2α = ln(2) / beta
• t1/2α = CL / Vd

Correct Answer: t1/2α = ln(2) / alpha

Q12. Which characteristic defines nonlinear (dose‑dependent) pharmacokinetics such as Michaelis–Menten elimination?

• Clearance changes with dose because elimination pathways become saturated at higher concentrations

Correct Answer: Clearance changes with dose because elimination pathways become saturated at higher concentrations

Q13. Which statement about whole‑body clearance is correct?

• Total body clearance is the sum of individual organ clearances (additivity of clearances)

Correct Answer: Total body clearance is the sum of individual organ clearances (additivity of clearances)

Q14. The plasma profile after an IV bolus in a two‑compartment model is typically written as which mathematical form?

• C(t) = A e^-alpha t + B e^-beta t (polyexponential with distribution and elimination terms)
• C(t) = C0 e^-kt only
• C(t) = (Dose × k12) / (Vd × t)

Correct Answer: C(t) = A e^-alpha t + B e^-beta t (polyexponential with distribution and elimination terms)

Q15. What is a primary practical use of compartmental pharmacokinetic models in therapeutic drug monitoring?

• To fit plasma concentration–time data and predict concentration profiles for dosage design and individualized therapy

Correct Answer: To fit plasma concentration–time data and predict concentration profiles for dosage design and individualized therapy

Q16. Which best distinguishes macroconstants from microconstants in a two‑compartment model?

• Macroconstants (A, B, alpha, beta) are observable biexponential parameters; microconstants (k12, k21, k10) are the underlying transfer/elimination rate constants between compartments

Correct Answer: Macroconstants (A, B, alpha, beta) are observable biexponential parameters; microconstants (k12, k21, k10) are the underlying transfer/elimination rate constants between compartments

Q17. In typical mammillary compartment models used in clinical pharmacokinetics, elimination is most commonly assumed to occur from which compartment?

• Central compartment (plasma) is the usual site of elimination

Correct Answer: Central compartment (plasma) is the usual site of elimination

Q18. For a constant IV infusion at rate R and first‑order elimination, the steady‑state concentration (Css) is given by which expression?

• Css = R / CL (infusion rate divided by clearance)
• Css = R × Vd
• Css = Dose / C0
• Css = ln(2) / t1/2

Correct Answer: Css = R / CL (infusion rate divided by clearance)

Q19. What does the steady‑state volume of distribution (Vss) represent conceptually?

• Apparent volume that accounts for distribution of drug at equilibrium between central and peripheral compartments

Correct Answer: Apparent volume that accounts for distribution of drug at equilibrium between central and peripheral compartments

Q20. Which approach is commonly used to estimate compartmental model parameters by fitting models to plasma concentration–time data?

• Nonlinear least squares (iterative compartmental model fitting to minimize weighted residuals)

Correct Answer: Nonlinear least squares (iterative compartmental model fitting to minimize weighted residuals)

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