One-compartment open model – extravascular administration MCQs With Answer

One-compartment open model – extravascular administration MCQs With Answer

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Introduction:

The one-compartment open model with extravascular administration describes how a drug is absorbed into systemic circulation, distributes uniformly in a single body compartment, and is eliminated. Key pharmacokinetic terms include absorption rate constant (ka), elimination rate constant (ke), bioavailability (F), peak concentration (Cmax), time to peak (Tmax), area under the curve (AUC), and half-life (t1/2). This model assumes first-order absorption and elimination and is essential for predicting plasma concentration-time profiles, dosing regimens, and interpreting flip-flop kinetics in oral, IM, or SC dosing. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. In a one-compartment open model after extravascular administration, the typical concentration–time equation for first-order absorption and elimination is:

  • C(t) = (F·Dose·ka)/(V·(ka − ke)) [e^(−ke·t) − e^(−ka·t)]
  • C(t) = (Dose/V) e^(−ke·t)
  • C(t) = (F·Dose/V) e^(−ka·t)
  • C(t) = (F·Dose·ke)/(V·(ke − ka)) [e^(−ka·t) − e^(−ke·t)]

Correct Answer: C(t) = (F·Dose·ka)/(V·(ka − ke)) [e^(−ke·t) − e^(−ka·t)]

Q2. Which parameter primarily determines Tmax after oral dosing in the one-compartment model?

  • Elimination rate constant (ke)
  • Absorption rate constant (ka)
  • Volume of distribution (V)
  • Bioavailability (F)

Correct Answer: Absorption rate constant (ka)

Q3. Flip-flop kinetics in extravascular dosing occur when:

  • ke >> ka
  • ka >> ke
  • ka ≈ ke
  • ka < ke (absorption slower than elimination)

Correct Answer: ka < ke (absorption slower than elimination)

Q4. Absolute bioavailability (F) is most directly estimated by comparing which two measures?

  • Tmax of oral vs IV dosing
  • Cmax of oral vs IV dosing
  • AUC after oral dosing to AUC after IV dosing (normalized by dose)
  • Half-life after oral vs IV dosing

Correct Answer: AUC after oral dosing to AUC after IV dosing (normalized by dose)

Q5. In a one-compartment extravascular model, which assumption is NOT required?

  • Instantaneous mixing within the compartment
  • First-order elimination from the compartment
  • Drug distribution into multiple deep tissue compartments
  • Linear pharmacokinetics within the studied range

Correct Answer: Drug distribution into multiple deep tissue compartments

Q6. For a single oral dose following first-order absorption, the time of maximum concentration (Tmax) is given by:

  • Tmax = ln(ka/ke)/(ka − ke)
  • Tmax = ln(ke/ka)/(ka − ke)
  • Tmax = 1/ka
  • Tmax = ln(2)/ke

Correct Answer: Tmax = ln(ka/ke)/(ka − ke)

Q7. Which effect will decreasing the absorption rate constant (ka) have on Cmax and Tmax, assuming other parameters fixed?

  • Cmax increases, Tmax decreases
  • Cmax decreases, Tmax increases
  • Both Cmax and Tmax increase
  • Neither Cmax nor Tmax change

Correct Answer: Cmax decreases, Tmax increases

Q8. The area under the curve (AUC) after extravascular dosing is directly proportional to:

  • Volume of distribution (V)
  • Absorption rate constant (ka)
  • F·Dose / Clearance (CL)
  • Tmax

Correct Answer: F·Dose / Clearance (CL)

Q9. In one-compartment extravascular kinetics, mean residence time (MRT) for a single dose with first-order absorption equals:

  • 1/ke
  • 1/ka
  • 1/ke + 1/ka
  • ln(2)/ke

Correct Answer: 1/ke + 1/ka

Q10. Which plot is useful to estimate the absorption rate constant (ka) by graphical methods in extravascular data?

  • Semi-log plot of concentration vs time during terminal phase
  • Semi-log plot of residuals after fitting elimination (method of residuals / curve stripping)
  • Linear plot of concentration vs time for entire profile
  • Log-log plot of dose vs AUC

Correct Answer: Semi-log plot of residuals after fitting elimination (method of residuals / curve stripping)

Q11. If bioavailability (F) is 0.5, Dose = 100 mg, clearance (CL) = 10 L/h, what is AUC (assuming linear kinetics)?

  • 0.5 mg·h/L
  • 5 mg·h/L
  • 1 mg·h/L
  • 10 mg·h/L

Correct Answer: 5 mg·h/L

Q12. Which statement best describes “rate-limited absorption” in extravascular dosing?

  • Elimination is slower than absorption so elimination determines profile
  • Absorption is slower than elimination and controls the decline of plasma concentration
  • Absorption is instantaneous and negligible
  • There is no absorption phase

Correct Answer: Absorption is slower than elimination and controls the decline of plasma concentration

Q13. For a one-compartment extravascular model, accumulation ratio (R) at steady state after repeated dosing with interval τ is given by:

  • R = 1 / (1 − e^(−ke·τ))
  • R = e^(−ke·τ)
  • R = 1 − e^(−ke·τ)
  • R = CL / V

Correct Answer: R = 1 / (1 − e^(−ke·τ))

Q14. In extravascular one-compartment kinetics, if ka is extremely large relative to ke, the profile approaches:

  • Zero-order absorption
  • IV bolus one-compartment decline (instantaneous absorption)
  • Multi-compartment distribution
  • Linear accumulation with time

Correct Answer: IV bolus one-compartment decline (instantaneous absorption)

Q15. Which parameter is NOT directly inferable from a single-dose extravascular concentration-time curve without IV reference?

  • ke (from terminal slope)
  • Relative ka (from absorption phase)
  • Absolute bioavailability (F)
  • Tmax

Correct Answer: Absolute bioavailability (F)

Q16. The method of residuals (“curve stripping”) is used to:

  • Estimate volume of distribution from Cmax only
  • Separate overlapping exponential phases to estimate ka and ke
  • Measure urine excretion directly
  • Convert oral dose to IV equivalent

Correct Answer: Separate overlapping exponential phases to estimate ka and ke

Q17. If two drugs have identical ka and ke but different F, how will their concentration-time curves differ?

  • They will have same Cmax but different Tmax
  • The drug with higher F will have higher AUC and higher Cmax
  • Tmax will shift with F
  • ke will change with F

Correct Answer: The drug with higher F will have higher AUC and higher Cmax

Q18. Which clinical factor can reduce oral bioavailability (F) in extravascular absorption?

  • Decreased hepatic first-pass metabolism
  • Increased gastric emptying time
  • Concurrent enzyme induction increasing presystemic metabolism
  • Increased drug solubility

Correct Answer: Concurrent enzyme induction increasing presystemic metabolism

Q19. To determine clearance (CL) from extravascular data you need:

  • Only Cmax and Tmax
  • F and AUC (CL = F·Dose / AUC)
  • V and ke but not dose
  • ka and Tmax only

Correct Answer: F and AUC (CL = F·Dose / AUC)

Q20. In a one-compartment model, elimination half-life (t1/2) is related to ke by:

  • t1/2 = ln(2)/ka
  • t1/2 = ln(2)/ke
  • t1/2 = 1/ke + 1/ka
  • t1/2 = V/CL

Correct Answer: t1/2 = ln(2)/ke

Q21. For extravascular dosing, which statement about Cmax is correct?

  • Cmax occurs at time zero for all extravascular routes
  • Cmax depends on ka, ke, F, Dose, and V
  • Cmax is independent of bioavailability
  • Cmax equals AUC divided by Tmax

Correct Answer: Cmax depends on ka, ke, F, Dose, and V

Q22. Which scenario is characteristic of absorption-limited elimination?

  • ka >> ke and elimination controls decline
  • ka << ke and absorption controls decline
  • ka = 0
  • Drug is administered IV

Correct Answer: ka << ke and absorption controls decline

Q23. When fitting extravascular one-compartment data, which parameter helps convert observed concentrations to amount in the body?

  • Absorption rate constant (ka)
  • Volume of distribution (V)
  • Bioavailability (F)
  • Clearance (CL)

Correct Answer: Volume of distribution (V)

Q24. Multiple dosing to steady state in a one-compartment extravascular model depends primarily on:

  • ka only
  • ke and dosing interval τ
  • F only
  • V only

Correct Answer: ke and dosing interval τ

Q25. Which mathematical change describes moving from IV bolus to extravascular dosing in one-compartment model?

  • Removal of elimination term
  • Addition of an absorption exponential term and factor F
  • Doubling of volume of distribution
  • Replacement of ka by ke

Correct Answer: Addition of an absorption exponential term and factor F

Q26. If ka = 2 h−1 and ke = 0.2 h−1, which is true?

  • Absorption is rate-limiting
  • Elimination is rate-limiting
  • ka and ke are equal
  • Flip-flop kinetics present

Correct Answer: Elimination is rate-limiting

Q27. In extravascular kinetics, increasing the dose while maintaining linear kinetics will:

  • Double ke
  • Double AUC and Cmax proportionally
  • Not change AUC
  • Change Tmax significantly

Correct Answer: Double AUC and Cmax proportionally

Q28. Which experimental approach clarifies whether oral absorption is first-order?

  • Measure AUC at two different doses and check proportionality
  • Only measure Tmax once
  • Compare V values
  • Assess taste of formulation

Correct Answer: Measure AUC at two different doses and check proportionality

Q29. In a one-compartment extravascular model, which condition will increase apparent half-life observed after oral dosing (compared to IV)?

  • F approaches 1
  • Very fast absorption (ka >> ke)
  • Very slow absorption (flip-flop, ka << ke)
  • Decrease in V only

Correct Answer: Very slow absorption (flip-flop, ka << ke)

Q30. For an orally administered drug in a one-compartment model, which strategy most directly increases Cmax without changing dose?

  • Decrease bioavailability (F)
  • Formulate to increase ka (faster absorption)
  • Increase clearance (CL)
  • Increase V

Correct Answer: Formulate to increase ka (faster absorption)

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