Relative and absolute bioavailability MCQs With Answer

Introduction

This set of MCQs focuses on relative and absolute bioavailability, a core topic in Modern Bio-Analytical Techniques for M.Pharm students. The questions cover fundamental definitions, calculation formulas, study designs, analytical considerations, factors influencing bioavailability (first-pass metabolism, formulation, route of administration), and interpretation of AUC/Cmax/Tmax data. Emphasis is placed on practical problem-solving — dose-normalized AUC comparisons, percent extrapolation, and distinguishing absolute versus relative measurements. These MCQs are designed to strengthen conceptual understanding and analytical skills required for designing bioavailability/bioequivalence studies and for interpreting bioanalytical results in preclinical and clinical settings.

Q1. Which expression correctly defines absolute bioavailability (F) of an orally administered drug compared to IV administration?

• (AUCpo / AUCiv) × (Doseiv / Dosepo)
• (AUCiv / AUCpo) × (Dosepo / Doseiv)
• (Cmax_po / Cmax_iv) × (Doseiv / Dosepo)
• (Tmax_po / Tmax_iv) × (Doseiv / Dosepo)

Correct Answer: (AUCpo / AUCiv) × (Doseiv / Dosepo)

Q2. Relative bioavailability is most appropriately used to compare which of the following?

• Oral formulation vs intravenous administration of the same drug
• Two oral formulations of the same drug when IV data are unavailable
• Systemic exposure of a metabolite vs parent drug after IV dosing
• Absolute clearance values between species

Correct Answer: Two oral formulations of the same drug when IV data are unavailable

Q3. If AUCpo = 50 µg·h/mL after a 200 mg oral dose and AUCiv = 100 µg·h/mL after a 50 mg IV dose, what is the absolute bioavailability?

• 25%
• 50%
• 100%
• 200%

Correct Answer: 50%

Q4. Which factor primarily causes reduced oral bioavailability due to hepatic first-pass effect?

• Low aqueous solubility in the intestinal lumen
• Extensive metabolism by hepatic enzymes before reaching systemic circulation
• Rapid gastric emptying
• High plasma protein binding

Correct Answer: Extensive metabolism by hepatic enzymes before reaching systemic circulation

Q5. Relative bioavailability (Frel) between test (T) and reference (R) formulations is calculated by which formula?

• (AUC_T / AUC_R) × (Dose_R / Dose_T)
• (AUC_R / AUC_T) × (Dose_T / Dose_R)
• (Cmax_T / Cmax_R) × (Dose_R / Dose_T)
• (Tmax_T / Tmax_R)

Correct Answer: (AUC_T / AUC_R) × (Dose_R / Dose_T)

Q6. Which analytical approach is standard for estimating AUC in bioavailability studies?

• Trapezoidal rule (non-compartmental analysis)
• Measuring only Cmax values
• Using only Tmax to estimate exposure
• Applying the Henderson-Hasselbalch equation

Correct Answer: Trapezoidal rule (non-compartmental analysis)

Q7. When calculating absolute bioavailability, why is dose normalization required?

• To adjust for differences in administered doses between routes
• To convert concentration units from µg/mL to mg/L
• To correct for protein binding differences
• To account for inter-subject variability in Tmax

Correct Answer: To adjust for differences in administered doses between routes

Q8. In a crossover bioavailability study, which design feature minimizes subject-related variability?

• Randomized sequence of treatments and washout periods
• Using a parallel-group design with different subjects
• Measuring only a single blood sample per subject
• Administering treatments without washout

Correct Answer: Randomized sequence of treatments and washout periods

Q9. AUC0–∞ is estimated as AUC0–t + Ct/kel. What is Ct/kel representing?

• Extrapolated area from the last measurable concentration to infinity
• Observed cumulative exposure up to time t
• Maximum observed concentration divided by Tmax
• Absolute clearance expressed in L/h

Correct Answer: Extrapolated area from the last measurable concentration to infinity

Q10. Regulatory guidance typically recommends that the percent of AUC extrapolated (AUCextrap%) should be:

• Less than or equal to 20%
• Greater than 50%
• Always zero for valid studies
• Between 30% and 40%

Correct Answer: Less than or equal to 20%

Q11. Which statement about absolute bioavailability values greater than 100% is correct?

• They are usually due to analytical or dosing errors; true F (vs IV) cannot exceed 100% for the same parent drug.
• They indicate the drug was amplified in circulation and are common for all oral drugs.
• They occur when Tmax is shorter after oral dosing than IV dosing.
• They are expected when bioavailability is calculated using Cmax instead of AUC.

Correct Answer: They are usually due to analytical or dosing errors; true F (vs IV) cannot exceed 100% for the same parent drug.

Q12. Which of the following will most likely increase oral bioavailability of a poorly soluble drug?

• Formulation as a lipid-based nanoemulsion to enhance absorption
• Increasing the dose without formulation change
• Adding a protein-binding enhancer
• Decreasing gastric pH to reduce solubility further

Correct Answer: Formulation as a lipid-based nanoemulsion to enhance absorption

Q13. If AUC_test = 120 µg·h/mL after 100 mg and AUC_ref = 100 µg·h/mL after 100 mg, what is the relative bioavailability (%) of test vs reference?

• 120%
• 83.3%
• 100%
• 20%

Correct Answer: 120%

Q14. Which clearance-related parameter directly affects absolute bioavailability when comparing oral to IV administration?

• Hepatic extraction ratio and first-pass metabolism
• The drug’s melting point
• Tablet disintegration time only
• Tissue partition coefficient exclusively

Correct Answer: Hepatic extraction ratio and first-pass metabolism

Q15. Which bioanalytical consideration is critical to ensure accurate AUC calculation in BA studies?

• Validated assay with appropriate sensitivity and accuracy across concentration range
• Using a surrogate metabolite without justification
• Sampling only pre-dose and at Tmax
• Not applying internal standard during LC-MS/MS analysis

Correct Answer: Validated assay with appropriate sensitivity and accuracy across concentration range

Q16. Incomplete absorption vs. presystemic metabolism: which experimental result most directly suggests extensive presystemic (first-pass) metabolism?

• Low oral AUC despite complete dissolution and high permeability, with high levels of metabolite in portal blood
• Low oral AUC with unchanged drug recovered in feces
• Delayed Tmax with high Cmax
• High urinary excretion of unchanged parent

Correct Answer: Low oral AUC despite complete dissolution and high permeability, with high levels of metabolite in portal blood

Q17. Which of the following best describes a situation where relative bioavailability is the preferred metric?

• Comparing two oral formulations of a drug to decide if a generic is equivalent to reference
• Determining the fraction of drug reaching systemic circulation after IV dosing
• Quantifying plasma protein binding differences between species
• Measuring renal clearance directly

Correct Answer: Comparing two oral formulations of a drug to decide if a generic is equivalent to reference

Q18. Which modeling approach can deconvolute input (absorption) function from plasma concentration-time data when IV data are available?

• Deconvolution using a known disposition function from IV data
• Direct trapezoidal rule without IV data
• Using only Cmax and Tmax measurements
• Applying Henderson–Hasselbalch deconvolution

Correct Answer: Deconvolution using a known disposition function from IV data

Q19. Which outcome is an acceptable justification for switching from absolute to relative bioavailability assessment?

• IV formulation is not practical or ethical for humans, so comparison between oral formulations is used
• IV data are available and show 100% exposure
• The test product matches IV exposure exactly
• There is no interest in systemic exposure

Correct Answer: IV formulation is not practical or ethical for humans, so comparison between oral formulations is used

Q20. Which parameter change would typically indicate improved bioavailability of a new oral formulation compared to the reference?

• Higher dose-normalized AUC and increased Cmax with similar safety profile
• Lower AUC and delayed Tmax only
• Unchanged AUC but reduced tablet weight
• Decreased solubility in biorelevant media

Correct Answer: Higher dose-normalized AUC and increased Cmax with similar safety profile

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