Permeability testing: In-vivo methods MCQs With Answer

Introduction: Permeability testing: In-vivo methods MCQs With Answer is designed for M.Pharm students to strengthen understanding of how drug absorption is assessed in living systems. This set focuses on in-vivo and in-situ techniques—such as single-pass intestinal perfusion, closed-loop methods, intestinal instillation, microdialysis and brain perfusion—highlighting practical procedures, key parameters (Papp, Peff, Fa), markers, data interpretation and limitations. Questions bridge theoretical principles with experimental considerations: selection of animal models, sample collection, influence of transporters and metabolism, and correlation with in vitro methods. Use these MCQs to prepare for exams and lab applications, emphasizing physiological complexity and translational relevance in permeability assessment.

Q1. Which statement best defines in-vivo permeability testing for oral drugs?

• Evaluation of drug diffusion across an artificial membrane in a cell-free system
• Assessment of drug absorption across tissues within a living organism
• Measurement of drug transport across cultured epithelial monolayers
• Determination of partition coefficient between octanol and water

Correct Answer: Assessment of drug absorption across tissues within a living organism

Q2. Which in-situ/in-vivo intestinal technique involves perfusing a defined intestinal segment while continuously delivering and collecting solution in a single pass?

• Closed-loop intestinal sac
• Single-pass intestinal perfusion (SPIP)
• Everted intestinal sac
• Caco-2 transwell assay

Correct Answer: Single-pass intestinal perfusion (SPIP)

Q3. Which non-absorbable marker is commonly used to correct for water flux in intestinal perfusion experiments?

• Phenol red
• Metoprolol
• Atenolol
• Propranolol

Correct Answer: Phenol red

Q4. The apparent permeability coefficient (Papp) in in-vivo or in-situ studies is most appropriately calculated by which relationship?

• Papp = (dQ/dt) / (A × C0)
• Papp = Cmax / Tmax
• Papp = log P (octanol/water)
• Papp = Fa × F

Correct Answer: Papp = (dQ/dt) / (A × C0)

Q5. Which factor is least likely to be captured by standard in-vitro Caco-2 assays but is assessed by in-vivo permeability studies?

• Expression of efflux and uptake transporters in native tissue
• Intrinsic passive membrane diffusion
• Membrane partitioning related to lipophilicity
• Permeability across a uniform epithelial monolayer

Correct Answer: Expression of efflux and uptake transporters in native tissue

Q6. In an in-situ single-pass intestinal perfusion experiment, which measured parameter is typically used to compute effective permeability (Peff)?

• Perfusate flow rate and change in drug concentration between inlet and outlet
• Plasma protein binding percentage only
• Partition coefficient into octanol
• Drug melting point

Correct Answer: Perfusate flow rate and change in drug concentration between inlet and outlet

Q7. Which model/method is primarily used for assessing drug entry across the blood–brain barrier in vivo?

• In situ brain perfusion (e.g., Oldendorf technique)
• Ussing chamber intestinal assay
• Parallel artificial membrane permeability assay (PAMPA)
• Caco-2 transwell monolayer

Correct Answer: In situ brain perfusion (e.g., Oldendorf technique)

Q8. Intestinal microdialysis in permeability studies is used mainly to measure which of the following?

• Unbound drug concentration in the intestinal interstitial fluid over time
• Total drug concentration within perfusate including bound fraction
• Membrane electrical resistance
• Partition coefficient in octanol/water

Correct Answer: Unbound drug concentration in the intestinal interstitial fluid over time

Q9. Which of the following is a major advantage of single-pass intestinal perfusion over closed-loop (recirculating) methods?

• Avoids accumulation of metabolites and maintains steady input concentration
• Produces higher residence time for maximal absorption
• Eliminates the need to measure inlet and outlet concentrations
• Requires less surgical preparation

Correct Answer: Avoids accumulation of metabolites and maintains steady input concentration

Q10. Which compound is often used as an example of a low-permeability, paracellular marker in permeability classification?

• Atenolol
• Metoprolol
• Lipophilic benzodiazepine
• Propranolol

Correct Answer: Atenolol

Q11. Which limitation is most characteristic of in-vivo permeability testing compared with in-vitro methods?

• Greater inter-animal and intra-subject variability and higher ethical/cost burden
• Inability to capture enzymatic metabolism
• Failure to model complex physiological variables
• Poor relevance to clinical absorption

Correct Answer: Greater inter-animal and intra-subject variability and higher ethical/cost burden

Q12. The Brain Uptake Index (BUI) is an in-vivo technique that measures which property of a test compound?

• Relative initial brain entry compared to a reference compound
• Fractional urinary excretion over 24 hours
• Lipophilicity as measured by octanol/water partitioning
• Plasma protein binding percentage

Correct Answer: Relative initial brain entry compared to a reference compound

Q13. During intestinal perfusion studies, why is correction for water flux necessary?

• To account for net absorption or secretion of water that alters drug concentration independent of absorption
• Because drug molecules chemically react with water
• To standardize pH across all experiments
• Because temperature fluctuations strongly change drug solubility

Correct Answer: To account for net absorption or secretion of water that alters drug concentration independent of absorption

Q14. Which of the following is an appropriate in-vivo method to directly measure absorption rate constant (Ka) after oral dosing?

• Plasma concentration–time profiling followed by pharmacokinetic modeling
• PAMPA static membrane diffusion
• Log P determination
• Shake-flask solubility test

Correct Answer: Plasma concentration–time profiling followed by pharmacokinetic modeling

Q15. Which intestinal region is most commonly used in rat SPIP experiments to represent major drug absorption for many orally dosed drugs?

• Jejunum
• Stomach fundus
• Duodenum only
• Colon exclusively

Correct Answer: Jejunum

Q16. In interpreting in-vivo permeability data, which physiological factor can reduce apparent permeability by creating an additional diffusion barrier near the epithelial surface?

• Unstirred water layer
• High blood flow to the tissue
• Increased bile salt concentration
• Enhanced paracellular pore size

Correct Answer: Unstirred water layer

Q17. Which option best describes a common purpose of using reference compounds (e.g., metoprolol, atenolol) in in-vivo permeability studies?

• To classify test drug permeability by comparison to well-characterized high/low permeability standards
• To act as excipients to improve solubility
• To inhibit gut enzymes non-specifically
• To alter gastric motility for slower absorption

Correct Answer: To classify test drug permeability by comparison to well-characterized high/low permeability standards

Q18. Which statement about recirculating (closed-loop) intestinal perfusion is correct?

• It can increase residence time but may allow metabolite accumulation and concentration changes over time
• It maintains a constant fresh input and single-pass output for precise concentration control
• It requires no surgical access to intestinal segments
• It is identical in design and interpretation to PAMPA

Correct Answer: It can increase residence time but may allow metabolite accumulation and concentration changes over time

Q19. Which measurement reflects the unbound fraction of drug available for permeation in in-vivo interstitial space assessments?

• Microdialysis sampling of extracellular fluid concentrations
• Total plasma concentration without correction
• Octanol/water partition coefficient
• Solid-phase extraction of tissue homogenate

Correct Answer: Microdialysis sampling of extracellular fluid concentrations

Q20. Which of the following is a common translational challenge when extrapolating in-vivo animal permeability results to humans?

• Species differences in transporter expression, intestinal geometry, and metabolic activity
• Exact matching of octanol/water partition coefficients across species
• Universal agreement in gastric pH between rodents and humans
• Identical intestinal surface area per body weight across species

Correct Answer: Species differences in transporter expression, intestinal geometry, and metabolic activity

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