Understanding measurement of bioavailability is essential for B.Pharm students focusing on pharmacokinetics, drug development, and therapeutic optimization. This topic covers principles and methods used to quantify the fraction and rate of drug absorbed into systemic circulation, including key parameters such as AUC, Cmax, Tmax, and absolute versus relative bioavailability. You will learn sampling strategies, analytical techniques (HPLC, LC-MS), non‑compartmental and compartmental analysis, and concepts of bioequivalence and formulation impact on absorption. Mastery of these concepts ensures accurate interpretation of bioavailability studies, regulatory requirements, bioanalytical validation, and clinical implications for dosing and safety. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which parameter best represents the total systemic exposure of a drug after administration?
- Maximum concentration reached in plasma
- Time to reach maximum concentration
- Area under the plasma concentration–time curve
- Elimination half‑life
Correct Answer: Area under the plasma concentration–time curve
Q2. Absolute bioavailability (F) of an oral drug is calculated by comparing which two values?
- AUC after oral dose and elimination half‑life after IV dose
- AUC after oral dose and AUC after intravenous dose normalized for dose
- Cmax after oral dose and total clearance after IV dose
- Tmax after oral dose and AUC after oral dose
Correct Answer: AUC after oral dose and AUC after intravenous dose normalized for dose
Q3. Which factor most directly reduces oral bioavailability through first‑pass hepatic metabolism?
- Low aqueous solubility
- High hepatic extraction ratio
- Rapid gastric emptying
- High plasma protein binding
Correct Answer: High hepatic extraction ratio
Q4. In non‑compartmental analysis, which method is commonly used to estimate AUC from time zero to last measurable concentration?
- Trapezoidal rule
- Logistic regression
- Fourier transform
- Maximum likelihood estimation
Correct Answer: Trapezoidal rule
Q5. Cmax indicates which aspect of drug exposure?
- Total drug elimination
- Maximum plasma concentration achieved
- Time required to eliminate half the drug
- Area under the curve per unit dose
Correct Answer: Maximum plasma concentration achieved
Q6. Tmax primarily provides information about which pharmacokinetic property?
- Rate of absorption
- Extent of metabolism
- Volume of distribution
- Renal clearance
Correct Answer: Rate of absorption
Q7. When designing a bioequivalence crossover study, the main advantage of a two‑period crossover is:
- Reduced need for analytical validation
- Minimizing intersubject variability by comparing within subjects
- Eliminating the need for washout periods
- Allowing different doses in each period
Correct Answer: Minimizing intersubject variability by comparing within subjects
Q8. Which analytical technique is most sensitive and specific for quantifying drug concentration in bioavailability studies?
- Ultraviolet–visible spectrophotometry
- High‑performance liquid chromatography with tandem mass spectrometry
- Paper chromatography
- Polarimetry
Correct Answer: High‑performance liquid chromatography with tandem mass spectrometry
Q9. In calculating AUC extrapolated to infinity (AUC0–∞), which parameter is required in addition to AUC0–t?
- Volume of distribution at steady state
- Last measurable concentration and terminal elimination rate constant
- Clearance and bioavailability fraction
- Cmax and Tmax
Correct Answer: Last measurable concentration and terminal elimination rate constant
Q10. Which is the correct formula for absolute bioavailability (F)?
- F = (DoseIV × AUCoral) / (Doseoral × AUCIV)
- F = (AUCoral / Tmax) × DoseIV
- F = (Doseoral × Cmax) / (DoseIV × AUCIV)
- F = (AUCIV × Doseoral) / (AUCoral × DoseIV)
Correct Answer: F = (DoseIV × AUCoral) / (Doseoral × AUCIV)
Q11. Which condition would most likely cause underestimation of AUC in a bioavailability study?
- Overly frequent early sampling
- Missing late samples needed to define terminal phase
- Using validated LC‑MS assay
- Normalizing AUC to dose
Correct Answer: Missing late samples needed to define terminal phase
Q12. Relative bioavailability compares which of the following?
- AUC of two different formulations or routes of the same drug
- Cmax of a drug to its elimination half‑life
- Tmax after oral and intramuscular dosing
- Volume of distribution between populations
Correct Answer: AUC of two different formulations or routes of the same drug
Q13. Why are internal standards used in bioanalytical assays for bioavailability measurement?
- To accelerate sample collection
- To correct for sample preparation and instrument variability
- To increase the half‑life of the analyte
- To change the analyte’s ionization efficiency arbitrarily
Correct Answer: To correct for sample preparation and instrument variability
Q14. Which statistical acceptance range is commonly used for AUC and Cmax in bioequivalence studies?
- 50–150%
- 80–125%
- 95–105%
- 60–140%
Correct Answer: 80–125%
Q15. The terminal elimination rate constant (lambda_z) is estimated from which portion of the concentration–time curve?
- Absorption phase
- Distribution phase only
- Terminal log‑linear decline phase
- Pre‑dose baseline
Correct Answer: Terminal log‑linear decline phase
Q16. In bioavailability studies, LLOQ refers to:
- Lowest level of quality assurance
- Lower limit of quantification of the assay
- Largest limit of quantification for safety samples
- Logical limit of quadratic fitting
Correct Answer: Lower limit of quantification of the assay
Q17. For highly permeable, highly soluble drugs, the dissolution rate often has what effect on bioavailability?
- It is the primary limiting factor
- It has minimal impact; absorption is rapid
- It causes extensive first‑pass metabolism
- It eliminates the need for bioanalytical methods
Correct Answer: It has minimal impact; absorption is rapid
Q18. Which sampling schedule principle is most important to accurately determine Cmax and Tmax?
- Frequent sampling around the expected absorption peak
- Only late sampling after 24 hours
- Single pre‑dose and single 24‑hour sample
- Avoiding sampling during the first hour
Correct Answer: Frequent sampling around the expected absorption peak
Q19. Which physiological factor typically decreases oral bioavailability in elderly patients?
- Increased gastric acid secretion
- Reduced hepatic blood flow and enzyme activity
- Faster renal elimination
- Increased intestinal surface area
Correct Answer: Reduced hepatic blood flow and enzyme activity
Q20. In a crossover bioequivalence study, what is the main purpose of the washout period?
- To increase Cmax for the second period
- To ensure previous treatment does not influence the next period
- To validate the analytical method again
- To adjust dose levels between periods
Correct Answer: To ensure previous treatment does not influence the next period
Q21. Which concept explains why a drug with high plasma protein binding may show reduced free concentration but unchanged total AUC?
- First‑pass metabolism
- Plasma protein binding equilibrium with rapid offset
- P‑glycoprotein efflux in the gut
- Incomplete dose recovery in urine
Correct Answer: Plasma protein binding equilibrium with rapid offset
Q22. Which bioanalytical validation parameter assesses the ability to recover known amounts of analyte from biological matrix?
- Stability
- Recovery
- Selectivity
- Ruggedness
Correct Answer: Recovery
Q23. Which scenario suggests a drug has low absolute bioavailability?
- High AUC after oral dosing compared to IV
- Markedly lower AUC after oral dosing despite equivalent doses
- Identical Cmax for oral and IV routes
- Rapid achievement of Tmax
Correct Answer: Markedly lower AUC after oral dosing despite equivalent doses
Q24. What is the primary regulatory goal of bioequivalence studies for generic drugs?
- To demonstrate identical impurities profile
- To show no clinically meaningful difference in rate and extent of absorption
- To replace clinical efficacy trials entirely
- To prove superiority over the reference product
Correct Answer: To show no clinically meaningful difference in rate and extent of absorption
Q25. Which calculation is used to determine the percentage of AUC extrapolated (AUCextrap%)?
- (AUC0–t / AUC0–∞) × 100
- ((AUC0–∞ − AUC0–t) / AUC0–∞) × 100
- (AUC0–t × lambda_z) / Cmax
- (Cmax − Cmin) / Tmax × 100
Correct Answer: ((AUC0–∞ − AUC0–t) / AUC0–∞) × 100
Q26. Which in vitro parameter is most commonly correlated with in vivo bioavailability for immediate‑release oral tablets?
- Dissolution profile in biorelevant media
- Melting point of the active ingredient
- Tablet color and shape
- Manufacturer’s recommended storage temperature
Correct Answer: Dissolution profile in biorelevant media
Q27. Which clearance parameter is directly used to calculate bioavailability when comparing oral and IV administration?
- Total systemic clearance from IV data
- Intrinsic clearance of the liver only
- Renal clearance multiplied by urine volume
- Clearance at steady state unrelated to dose
Correct Answer: Total systemic clearance from IV data
Q28. For a drug undergoing extensive first‑pass metabolism, which formulation strategy can improve oral bioavailability?
- Designing an immediate‑release capsule
- Developing a prodrug to bypass first‑pass metabolism
- Reducing particle size without changing permeability
- Increasing tablet hardness
Correct Answer: Developing a prodrug to bypass first‑pass metabolism
Q29. In a pharmacokinetic study, which outcome indicates acceptable assay precision?
- Inter‑assay coefficient of variation of 20–30%
- Intra‑assay coefficient of variation ≤15% at relevant concentrations
- Recovery less than 30%
- No use of internal standard
Correct Answer: Intra‑assay coefficient of variation ≤15% at relevant concentrations
Q30. Which of the following best describes bioequivalence based on pharmacokinetic criteria?
- Two products with identical formulation excipients
- Two products with statistically similar AUC and Cmax within predefined limits
- Two products that have the same color and shape
- Two products that are manufactured in the same facility
Correct Answer: Two products with statistically similar AUC and Cmax within predefined limits
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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