Permeability testing: In-situ methods MCQs With Answer

Permeability testing: In-situ methods MCQs With Answer is designed to strengthen M.Pharm students’ understanding of in-situ permeability techniques used in drug absorption studies. This short quiz collection emphasizes practical methods such as single-pass intestinal perfusion (SPIP), closed-loop perfusion, mesenteric blood sampling, and corrections for water flux and non-absorbable markers. Questions cover experimental setup, calculations of effective permeability (Peff), selection of markers, sampling strategies, species differences, confounding factors like metabolism and anaesthesia, and interpretation of data. These MCQs will help you connect theoretical equations with hands-on considerations and critical troubleshooting for reliable permeability assessment in preclinical research.

Q1. What is the primary advantage of single-pass intestinal perfusion (SPIP) over closed-loop in-situ perfusion?

• Allows repeated sampling from the same luminal content
• Provides better control of luminal residence time and steady-state concentrations
• Eliminates the need for non-absorbable markers
• Prevents any first-pass metabolism in the intestinal segment

Correct Answer: Provides better control of luminal residence time and steady-state concentrations

Q2. In the SPIP method, which parameter does the equation Peff = -(Q / (2πrL)) ln(Cout/Cin) directly depend on?

• Perfusion flow rate (Q), intestinal radius (r) and segment length (L)
• Blood flow to the intestine only
• Systemic plasma concentration of the drug
• Type of anesthesia used

Correct Answer: Perfusion flow rate (Q), intestinal radius (r) and segment length (L)

Q3. Why is a non-absorbable marker such as phenol red used in in-situ perfusion studies?

• To enhance drug absorption by altering pH
• To correct for water flux and luminal volume changes
• To inhibit intestinal metabolism of the test drug
• To increase solubility of lipophilic drugs

Correct Answer: To correct for water flux and luminal volume changes

Q4. When correcting outlet drug concentration for water flux using a non-absorbable marker, which mathematical operation is typically applied?

• Multiplying Cout by the ratio Cin_marker / Cout_marker
• Subtracting the marker concentration from Cout
• Dividing Cout by flow rate Q
• Adding the marker concentration to Cout

Correct Answer: Multiplying Cout by the ratio Cin_marker / Cout_marker

Q5. Which in-situ sampling method provides direct assessment of absorbed drug appearance in blood draining the intestine?

• Everted intestinal sac
• Mesenteric (or portal) vein blood sampling during perfusion
• PAMPA membrane assay
• In vitro Caco-2 transport alone

Correct Answer: Mesenteric (or portal) vein blood sampling during perfusion

Q6. A major limitation of mesenteric blood sampling in permeability studies is:

• It cannot detect first-pass hepatic metabolism
• It is insensitive to low permeability compounds
• It requires complex surgical cannulation and can alter blood flow
• It does not allow calculation of effective permeability (Peff)

Correct Answer: It requires complex surgical cannulation and can alter blood flow

Q7. Which assumption is essential for applying the steady-state single-pass perfusion equation to calculate Peff?

• Instantaneous distribution of drug into systemic circulation
• No net secretion or production of the drug in the lumen
• Complete dissolution of the drug in plasma
• Constant intestinal diameter between animals only

Correct Answer: No net secretion or production of the drug in the lumen

Q8. How does increasing perfusion flow rate (Q) in SPIP generally affect apparent outlet concentration (Cout) for a highly permeable drug?

• Cout increases because residence time decreases, reducing absorption fraction
• Cout decreases due to enhanced drug extraction from blood
• Cout remains unchanged for all drugs
• Cout becomes equal to systemic plasma concentration

Correct Answer: Cout increases because residence time decreases, reducing absorption fraction

Q9. Which of the following factors can falsely increase calculated Peff in in-situ perfusion experiments?

• Using an effective non-absorbable marker
• Ignoring intestinal water secretion and not correcting Cout
• Maintaining physiological temperature
• Careful cannulation minimizing trauma

Correct Answer: Ignoring intestinal water secretion and not correcting Cout

Q10. Closed-loop (recirculating) intestinal perfusion is particularly useful when:

• Rapid estimation of Peff with minimal surgery is required
• Longer exposure and equilibration of poorly soluble compounds are needed
• One wants to avoid any systemic sampling
• Markers for water flux are not available

Correct Answer: Longer exposure and equilibration of poorly soluble compounds are needed

Q11. In in-situ perfusion, what is the main reason to anesthetize the animal carefully and monitor physiological parameters?

• Anesthesia enhances intestinal permeability predictably for all drugs
• Changes in blood pressure, intestinal motility and blood flow can alter absorption and Peff
• Anesthesia eliminates the need for non-absorbable markers
• Anesthetics directly increase drug solubility

Correct Answer: Changes in blood pressure, intestinal motility and blood flow can alter absorption and Peff

Q12. Which correction is commonly applied when calculating Peff from concentrations to account for longitudinal diffusion and mixing artifacts?

• pH correction using buffer capacity
• Marker-based concentration correction and logarithmic transformation of Cin/Cout
• Temperature normalization to 37°C only
• Normalization by animal body weight without marker

Correct Answer: Marker-based concentration correction and logarithmic transformation of Cin/Cout

Q13. Why are jejunal segments often chosen for in-situ permeability studies in rats?

• Jejunum generally shows minimal metabolizing enzymes
• It offers a large absorptive surface and represents major site of small molecule absorption
• It is the easiest segment to cannulate with no surgical impact
• Jejunum lacks mucus, simplifying interpretation

Correct Answer: It offers a large absorptive surface and represents major site of small molecule absorption

Q14. Which of the following describes a practical way to account for drug loss due to adsorption to tubing during perfusion?

• Use higher drug concentrations so adsorption is negligible
• Precondition tubing with drug solution and measure blank adsorption prior to experiment
• Avoid using markers and perform perfusion faster
• Rely solely on systemic blood sampling to avoid tubing effects

Correct Answer: Precondition tubing with drug solution and measure blank adsorption prior to experiment

Q15. In in-situ perfusion, first-pass intestinal metabolism can confound permeability estimates because:

• Metabolism increases luminal drug concentration artificially
• Metabolism reduces the fraction of parent drug appearing in blood or perfusate, underestimating permeability
• Metabolism does not affect perfusion outcomes at all
• Metabolism solely affects the non-absorbable marker

Correct Answer: Metabolism reduces the fraction of parent drug appearing in blood or perfusate, underestimating permeability

Q16. Effective permeability (Peff) values from rat SPIP are often scaled to humans using which consideration?

• Direct molar equivalence without anatomical scaling
• Correction for surface area, transit time, and species-specific blood flow differences
• Assuming identical intestinal radii across species
• Only pH differences are considered

Correct Answer: Correction for surface area, transit time, and species-specific blood flow differences

Q17. Which in-situ technique is most appropriate to assess colonic permeability separately from small intestinal absorption?

• SPIP in the jejunum
• Closed-loop perfusion localized to a colonic segment
• PAMPA assay
• Caco-2 monolayer only

Correct Answer: Closed-loop perfusion localized to a colonic segment

Q18. Which statement about permeability classification using in-situ Peff is correct?

• High Peff guarantees high oral bioavailability irrespective of solubility and metabolism
• Low Peff suggests absorption-rate limitation, but solubility and first-pass effects must also be considered
• Peff alone can predict transporter-mediated efflux without additional assays
• Peff values are identical across all intestinal regions and species

Correct Answer: Low Peff suggests absorption-rate limitation, but solubility and first-pass effects must also be considered

Q19. During SPIP, stable steady-state sampling is important because:

• It maximizes first-pass metabolism
• It ensures measured Cout reflects true absorptive loss rather than transient mixing or sampling artifacts
• It eliminates the need to measure Cin
• It allows complete degradation of the drug in the lumen

Correct Answer: It ensures measured Cout reflects true absorptive loss rather than transient mixing or sampling artifacts

Q20. Which experimental control best distinguishes between net absorptive transport and luminal degradation in an in-situ perfusion study?

• Using a non-absorbable marker only
• Simultaneous measurement of parent drug and major metabolites in both perfusate and mesenteric blood
• Lowering perfusion temperature to reduce metabolism
• Performing the experiment without anaesthesia

Correct Answer: Simultaneous measurement of parent drug and major metabolites in both perfusate and mesenteric blood

Download