One-compartment open model – IV bolus administration MCQs With Answer

One-compartment open model – IV bolus administration MCQs With Answer

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Understanding the One-compartment open model with IV bolus administration is essential for B. Pharm students studying pharmacokinetics. This model assumes instantaneous distribution into a single, well-mixed compartment and monoexponential elimination described by the elimination rate constant (kel). Key concepts include calculation of initial concentration (C0), volume of distribution (Vd), half-life (t1/2), clearance (CL), AUC and concentration–time profiles using Ct = C0 e-kel t. Mastery of these principles helps with dose calculation, interpretation of Vd and CL, and log-linear plotting skills. These MCQs focus on theory, calculations, units, assumptions and clinical implications to strengthen your problem-solving. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which statement best describes the one-compartment open model after IV bolus administration?

  • Instantaneous distribution into a single well-mixed compartment with monoexponential elimination
  • Distribution into multiple tissue compartments with biexponential elimination
  • Elimination follows zero-order kinetics regardless of concentration
  • Drug remains entirely in the plasma without tissue distribution

Correct Answer: Instantaneous distribution into a single well-mixed compartment with monoexponential elimination

Q2. What is the correct expression for initial concentration (C0) immediately after an IV bolus in a one-compartment model?

  • C0 = Dose × Vd
  • C0 = Dose / Vd
  • C0 = Dose / CL
  • C0 = CL / Dose

Correct Answer: C0 = Dose / Vd

Q3. How is the elimination rate constant (kel) related to half-life (t1/2) in first-order kinetics?

  • kel = t1/2 / 0.693
  • kel = 0.693 × t1/2
  • kel = 0.693 / t1/2
  • kel = ln(t1/2)

Correct Answer: kel = 0.693 / t1/2

Q4. For an IV bolus one-compartment model, which equation gives the area under the plasma concentration–time curve (AUC)?

  • AUC = C0 × kel
  • AUC = Dose × Vd
  • AUC = Dose / CL
  • AUC = Vd / CL

Correct Answer: AUC = Dose / CL

Q5. Which relationship correctly links clearance (CL), volume of distribution (Vd) and elimination rate constant (kel)?

  • CL = Vd / kel
  • CL = Vd × kel
  • CL = kel / Vd
  • CL = Vd + kel

Correct Answer: CL = Vd × kel

Q6. On a semilogarithmic plot (ln concentration vs time) for a one-compartment IV bolus, what does the slope represent?

  • Slope = +kel
  • Slope = -kel
  • Slope = CL
  • Slope = Vd

Correct Answer: Slope = -kel

Q7. What are the usual units used for volume of distribution (Vd)?

  • Mass (mg)
  • Time (h)
  • Liters (L) or liters per kg (L/kg)
  • Concentration (mg/L)

Correct Answer: Liters (L) or liters per kg (L/kg)

Q8. What are common units for clearance (CL)?

  • mg
  • L/h or mL/min (volume per unit time)
  • hour (h)
  • unitless

Correct Answer: L/h or mL/min (volume per unit time)

Q9. Which equation describes plasma concentration at time t after an IV bolus in a one-compartment first-order model?

  • Ct = C0 + kel × t
  • Ct = C0 × e^(kel t)
  • Ct = C0 × e^(-kel t)
  • Ct = Dose / (Vd × kel)

Correct Answer: Ct = C0 × e^(-kel t)

Q10. When plotting ln(concentration) versus time and extrapolating the terminal line back to time zero, what is the intercept?

  • The elimination rate constant kel
  • The area under the curve (AUC)
  • Extrapolated y-intercept equals C0 (initial concentration)
  • The clearance value

Correct Answer: Extrapolated y-intercept equals C0 (initial concentration)

Q11. A straight line on a semilog concentration–time plot most directly indicates which type of elimination?

  • Zero-order elimination
  • First-order (single exponential) elimination
  • Michaelis–Menten elimination
  • No elimination (steady concentration)

Correct Answer: First-order (single exponential) elimination

Q12. In first-order elimination within a one-compartment model, how does half-life behave with changing dose?

  • Half-life increases with dose
  • Half-life decreases with dose
  • Half-life is independent of dose
  • Half-life becomes zero at high dose

Correct Answer: Half-life is independent of dose

Q13. A very large apparent Vd (much greater than total body water) typically suggests what about a drug?

  • It is confined to plasma
  • Extensive distribution into tissues or strong tissue binding
  • Rapid renal excretion only
  • Insufficient absorption from the gut

Correct Answer: Extensive distribution into tissues or strong tissue binding

Q14. If a drug has an apparent Vd smaller than plasma volume, what is the likely interpretation?

  • The drug is highly lipophilic and accumulates in fat
  • The drug is mainly confined to plasma, likely with high plasma protein binding
  • The drug is primarily intracellular
  • The drug has very rapid tissue distribution

Correct Answer: The drug is mainly confined to plasma, likely with high plasma protein binding

Q15. Which formula gives the loading dose needed to achieve a target plasma concentration immediately after an IV bolus?

  • Loading dose = CL × Css
  • Loading dose = Target concentration × Vd
  • Loading dose = AUC × kel
  • Loading dose = Vd / target concentration

Correct Answer: Loading dose = Target concentration × Vd

Q16. For continuous IV infusion, what is the maintenance infusion rate required to achieve a desired steady-state concentration (Css)?

  • Rate = Vd × Css
  • Rate = Kel × Vd
  • Rate = CL × Css
  • Rate = Dose / AUC

Correct Answer: Rate = CL × Css

Q17. Which equality holds true for AUC in a one-compartment IV bolus model with first-order elimination?

  • AUC = C0 × kel
  • AUC = C0 / kel = Dose / CL
  • AUC = Vd / Dose
  • AUC = kel / C0

Correct Answer: AUC = C0 / kel = Dose / CL

Q18. What is the standard practical method to estimate kel from concentration–time data?

  • Plot concentration vs time on linear scale and measure intercept
  • Plot ln(concentration) vs time and determine slope (slope = -kel)
  • Integrate the curve numerically without transformation
  • Measure time to reach peak concentration only

Correct Answer: Plot ln(concentration) vs time and determine slope (slope = -kel)

Q19. What is the absolute bioavailability (F) for an IV bolus dose?

  • F = 0 (no bioavailability)
  • F = 0.5 (50%)
  • F = 1 (100%)
  • F depends on hepatic extraction only

Correct Answer: F = 1 (100%)

Q20. How does doubling systemic clearance (CL) affect the AUC for the same IV bolus dose (assuming linear kinetics)?

  • AUC doubles
  • AUC remains unchanged
  • AUC is halved
  • AUC increases by fourfold

Correct Answer: AUC is halved

Q21. If elimination follows zero-order kinetics, what is the expected shape on a semilog concentration–time plot?

  • A straight line
  • A parabola
  • A curve that is not linear (not a straight line)
  • Vertical line

Correct Answer: A curve that is not linear (not a straight line)

Q22. How is C0 practically obtained when the earliest measured concentration is after some distribution or sampling delay?

  • Use the highest observed concentration directly as C0
  • Extrapolate the terminal log-linear phase back to time zero to estimate C0
  • Calculate C0 as AUC × kel
  • Assume C0 equals steady-state concentration

Correct Answer: Extrapolate the terminal log-linear phase back to time zero to estimate C0

Q23. Which equation allows calculation of clearance from a single IV bolus dose and measured AUC?

  • CL = Dose × AUC
  • CL = Dose / AUC
  • CL = AUC / Dose
  • CL = Dose × C0

Correct Answer: CL = Dose / AUC

Q24. Numerical relation: If a drug has t1/2 = 4 hours, what is kel (approx)?

  • kel ≈ 0.173 h⁻¹
  • kel ≈ 2.77 h⁻¹
  • kel ≈ 0.693 h
  • kel ≈ 4 h⁻¹

Correct Answer: kel ≈ 0.173 h⁻¹

Q25. How does high plasma protein binding typically affect apparent Vd?

  • Increases Vd dramatically because protein-bound drug enters tissues easily
  • Decreases apparent Vd because more drug remains in plasma bound to proteins
  • Has no effect on Vd
  • Changes Vd only if drug is renally excreted unchanged

Correct Answer: Decreases apparent Vd because more drug remains in plasma bound to proteins

Q26. To achieve a desired concentration Ct at a future time t after IV bolus, which equation gives the required bolus dose?

  • Dose = Ct / Vd × e^(-kel t)
  • Dose = Ct × Vd × e^(kel t)
  • Dose = Ct × CL / kel
  • Dose = Ct × AUC

Correct Answer: Dose = Ct × Vd × e^(kel t)

Q27. Which pharmacokinetic parameter depends on both Vd and CL?

  • Clearance (CL) only depends on Vd
  • Volume of distribution (Vd) only depends on CL
  • Half-life (t1/2) depends on both Vd and CL
  • AUC depends on Vd but not on CL

Correct Answer: Half-life (t1/2) depends on both Vd and CL

Q28. An observed apparent Vd ≈ 0.05 L/kg most likely corresponds to which distribution pattern?

  • Predominantly intracellular distribution
  • Extensive tissue binding, especially fat
  • Mainly confined to plasma
  • Extraordinarily high distribution into bone

Correct Answer: Mainly confined to plasma

Q29. Which formula is used to calculate apparent volume of distribution from a bolus dose and extrapolated C0?

  • Vd = Dose × C0
  • Vd = Dose / C0
  • Vd = CL / kel
  • Vd = AUC / Dose

Correct Answer: Vd = Dose / C0

Q30. In which clinical situation is the simple one-compartment IV bolus model likely inappropriate?

  • When rapid equilibrium between plasma and tissues is achieved instantly
  • When a distinct distribution (alpha) phase produces a biexponential decline (multi-compartment behavior)
  • When elimination is strictly first-order and monoexponential
  • When the drug is administered orally with complete absorption

Correct Answer: When a distinct distribution (alpha) phase produces a biexponential decline (multi-compartment behavior)

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