Absolute and relative bioavailability MCQs With Answer

Absolute and relative bioavailability MCQs With Answer

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Introduction

Understanding absolute and relative bioavailability is essential for B. Pharm students studying pharmacokinetics, formulation development, and therapeutic drug monitoring. Absolute bioavailability quantifies the fraction of an administered dose reaching systemic circulation compared with an intravenous reference, using parameters like AUC, Cmax and Tmax. Relative bioavailability compares two non‑intravenous formulations or routes, informing bioequivalence and formulation optimization. Key concepts include first‑pass metabolism, absorption rate, extraction ratio, study design, and analytical measurement of AUC. These MCQs cover calculations, experimental design, regulatory criteria and clinical implications to prepare you for exams and real‑world applications. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the correct formula for absolute bioavailability (F) when comparing an oral dose to an IV reference?

  • F = (AUCiv / AUCpo) × (Dose po / Dose iv)
  • F = (AUCpo / AUCiv) × (Dose iv / Dose po)
  • F = (Cmax po / Cmax iv) × (Dose iv / Dose po)
  • F = (Tmax po / Tmax iv) × (Dose iv / Dose po)

Correct Answer: F = (AUCpo / AUCiv) × (Dose iv / Dose po)

Q2. Which parameter is most directly used to calculate bioavailability?

  • Cmax (maximum plasma concentration)
  • Tmax (time to reach Cmax)
  • AUC (area under the plasma concentration–time curve)
  • Half‑life (t1/2)

Correct Answer: AUC (area under the plasma concentration–time curve)

Q3. Relative bioavailability is most appropriate when:

  • An IV formulation is available and used as reference
  • Comparing two oral formulations where IV data are not available
  • Measuring absolute systemic availability compared to IV
  • Assessing drug clearance at steady state

Correct Answer: Comparing two oral formulations where IV data are not available

Q4. A drug has high first‑pass metabolism. How does this affect oral absolute bioavailability?

  • It increases absolute bioavailability
  • It decreases absolute bioavailability
  • It has no effect on absolute bioavailability
  • It only affects Tmax, not bioavailability

Correct Answer: It decreases absolute bioavailability

Q5. In bioequivalence studies the usual acceptance range for 90% confidence intervals of AUC and Cmax ratios is:

  • 50%–150%
  • 80%–125%
  • 90%–110%
  • 70%–130%

Correct Answer: 80%–125%

Q6. Which statistical transformation is typically applied to AUC and Cmax before analysis in bioequivalence studies?

  • No transformation
  • Square root transformation
  • Logarithmic transformation
  • Reciprocal transformation

Correct Answer: Logarithmic transformation

Q7. If Dose_iv = 10 mg, Dose_po = 50 mg, AUC_iv = 2000 ng·h/mL and AUC_po = 800 ng·h/mL, what is F (absolute bioavailability)?

  • 0.08 (8%)
  • 0.20 (20%)
  • 0.40 (40%)
  • 0.80 (80%)

Correct Answer: 0.40 (40%)

Q8. Which of the following best describes Cmax?

  • The total drug eliminated over time
  • The highest observed plasma concentration after dosing
  • The time when half the dose is absorbed
  • The area under the concentration–time curve

Correct Answer: The highest observed plasma concentration after dosing

Q9. Which experimental design is most commonly used for bioequivalence studies?

  • Parallel group trial without crossover
  • Randomized two‑period crossover design
  • Open‑label single arm study
  • Case‑control study

Correct Answer: Randomized two‑period crossover design

Q10. What does Tmax indicate in pharmacokinetics?

  • The fraction of dose absorbed
  • The time to reach maximum plasma concentration
  • The elimination half‑life
  • The total exposure to the drug

Correct Answer: The time to reach maximum plasma concentration

Q11. AUC is reported in which of the following units?

  • mg/L
  • ng/mL
  • ng·h/mL
  • h

Correct Answer: ng·h/mL

Q12. Why is an intravenous (IV) dose used as reference for absolute bioavailability?

  • IV dosing eliminates absorption variability and first‑pass loss
  • IV dosing is cheaper and easier
  • IV dosing always produces a lower AUC
  • IV dosing shortens the half‑life significantly

Correct Answer: IV dosing eliminates absorption variability and first‑pass loss

Q13. If two oral formulations have relative bioavailability of 0.95, what does this imply?

  • The test formulation has 95% of systemic exposure of reference formulation
  • The test formulation has 5% more exposure than reference formulation
  • Both formulations are not comparable
  • The test formulation is 95% absorbed compared to IV

Correct Answer: The test formulation has 95% of systemic exposure of reference formulation

Q14. Which factor does NOT typically affect oral bioavailability?

  • Gastric pH
  • Drug solubility and dissolution rate
  • Route of IV administration
  • First‑pass hepatic metabolism

Correct Answer: Route of IV administration

Q15. When urinary excretion of unchanged drug is used to estimate absolute bioavailability, which parameter is compared?

  • Cmax of oral and IV
  • Amount excreted unchanged after oral and IV doses (Ae)
  • Tmax of oral and IV
  • Half‑life after oral and IV

Correct Answer: Amount excreted unchanged after oral and IV doses (Ae)

Q16. Hepatic extraction ratio (E) close to 1 implies:

  • Low first‑pass metabolism
  • High first‑pass metabolism
  • Complete oral bioavailability
  • Minimal hepatic clearance

Correct Answer: High first‑pass metabolism

Q17. Which of the following is a reason to perform a relative bioavailability study instead of an absolute one?

  • An IV formulation is available and safe
  • The new formulation is identical to the reference
  • IV formulation is not available or unethical
  • Absolute bioavailability is greater than 100%

Correct Answer: IV formulation is not available or unethical

Q18. For a drug with low solubility but high permeability, which Biopharmaceutics Classification System (BCS) class is most likely?

  • Class I – high solubility, high permeability
  • Class II – low solubility, high permeability
  • Class III – high solubility, low permeability
  • Class IV – low solubility, low permeability

Correct Answer: Class II – low solubility, high permeability

Q19. Which parameter can change without affecting absolute bioavailability?

  • AUC
  • Cmax
  • Fraction absorbed (F)
  • Total systemic exposure

Correct Answer: Cmax

Q20. In a crossover bioequivalence study, what is the purpose of a washout period?

  • To randomize subjects
  • To allow drug from the first period to be eliminated before the second
  • To increase Cmax for the second period
  • To change the formulation between periods

Correct Answer: To allow drug from the first period to be eliminated before the second

Q21. Which regulatory parameter is most commonly used to claim bioequivalence?

  • Comparative Tmax only
  • Geometric mean ratios with 90% CI for AUC and Cmax within 80%–125%
  • Peak-to-trough fluctuation comparison
  • Absolute bioavailability > 50%

Correct Answer: Geometric mean ratios with 90% CI for AUC and Cmax within 80%–125%

Q22. Which analytical method is frequently used to quantify plasma drug concentrations for AUC calculations?

  • High‑performance liquid chromatography (HPLC)
  • pH titration
  • Microscopy
  • Thermogravimetric analysis

Correct Answer: High‑performance liquid chromatography (HPLC)

Q23. If a formulation shows AUC ratio (test/reference) of 1.30 with 90% CI 1.10–1.54, is it bioequivalent by standard criteria?

  • Yes, because ratio > 1
  • No, because 90% CI exceeds 80%–125% limits
  • Yes, because lower CI > 0.8
  • No, because point estimate is less than 1.5

Correct Answer: No, because 90% CI exceeds 80%–125% limits

Q24. Which scenario would most likely result in apparent absolute bioavailability greater than 100%?

  • Analytical error or incorrect dose accounting
  • Perfect absorption with no clearance
  • Complete first‑pass metabolism
  • Zero order elimination

Correct Answer: Analytical error or incorrect dose accounting

Q25. The extraction ratio (E) of a drug is defined as:

  • The fraction of drug extracted by the liver from the blood during one pass
  • The fraction of dose excreted unchanged in urine
  • The fraction of drug absorbed from the GI tract
  • The fraction of drug bound to plasma proteins

Correct Answer: The fraction of drug extracted by the liver from the blood during one pass

Q26. Which approach can improve oral bioavailability of a poorly soluble drug?

  • Formulate as a salt or use solubilizing excipients
  • Decrease dose without formulation change
  • Switch to extended release without solubility enhancement
  • Administer with a proton pump inhibitor always

Correct Answer: Formulate as a salt or use solubilizing excipients

Q27. For drugs with significant first‑pass effect, which route will typically give higher systemic availability?

  • Oral route
  • Rectal route
  • Intravenous route
  • Inhalation with pulmonary absorption negligible

Correct Answer: Intravenous route

Q28. Bioavailability studies should control which of the following to reduce variability?

  • Subject diet, concomitant drugs and dosing conditions
  • Only the color of the capsule
  • Ambient temperature during analysis only
  • Subject hair color

Correct Answer: Subject diet, concomitant drugs and dosing conditions

Q29. Which is TRUE about absolute bioavailability values?

  • They are always between 0 and 1 and can never exceed 1
  • They can be greater than 1 with proper analytical technique
  • Values >1 indicate increased absorption compared to IV
  • Values >1 usually indicate error or improper normalization

Correct Answer: Values >1 usually indicate error or improper normalization

Q30. Which clinical implication is most relevant when two formulations are not bioequivalent?

  • No impact; formulations are interchangeable
  • Potential for altered therapeutic effect or toxicity when switching products
  • Guaranteed better patient adherence
  • Shorter half‑life for both formulations

Correct Answer: Potential for altered therapeutic effect or toxicity when switching products

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