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
