Biopharmaceutical factors affecting bioavailability MCQs With Answer

Biopharmaceutical factors affecting bioavailability MCQs With Answer

This set of MCQs is designed for M.Pharm students to deepen understanding of biopharmaceutical determinants that control drug bioavailability. Questions cover physicochemical properties (solubility, permeability, pKa, polymorphism), physiological aspects (gastric emptying, intestinal transit, first-pass metabolism, bile flow), formulation influences (particle size, salt form, excipients, prodrugs) and transport/metabolic mechanisms (P-glycoprotein efflux, enzyme induction/inhibition, enterohepatic recycling). Emphasis is placed on linking mechanisms to in vivo outcomes (Cmax, AUC, Tmax), classification systems (BCS) and strategies to improve oral absorption. These items help prepare for advanced coursework, viva voce and competitive examinations by testing applied concepts and problem-solving in biopharmaceutics.

Q1. Which of the following most directly determines whether a drug is classified as high or low permeability in the Biopharmaceutics Classification System (BCS)?

• Water solubility at pH 7.4
• Fraction absorbed in humans (fa) or extent of absorption
• Intrinsic dissolution rate
• Particle size distribution

Correct Answer: Fraction absorbed in humans (fa) or extent of absorption

Q2. According to Noyes–Whitney equation, which factor most directly increases the dissolution rate of a poorly soluble drug?

• Increasing particle size
• Decreasing surface area
• Adding a surfactant to increase wettability
• Reducing temperature

Correct Answer: Adding a surfactant to increase wettability

Q3. A weakly basic drug with pKa 8.5 is administered orally. In which GI region will it mostly be unionized and hence better absorbed by passive diffusion?

• Stomach (pH ~1.5–3.5)
• Proximal small intestine (pH ~5–6)
• Distal small intestine (pH ~6–7.5)
• Colon (pH ~7–8)

Correct Answer: Colon (pH ~7–8)

Q4. Which physiological change is most likely to reduce the oral bioavailability of a high-extraction-ratio drug?

• Decreased hepatic blood flow
• Increased gastric pH
• Slower gastric emptying
• Enhanced intestinal permeability

Correct Answer: Decreased hepatic blood flow

Q5. P-glycoprotein (P-gp) efflux in enterocytes typically affects bioavailability by which mechanism?

• Enhancing passive absorption across the apical membrane
• Pumping drug back into the intestinal lumen, lowering net absorption
• Increasing first-pass hepatic metabolism directly
• Improving solubility by micellar formation

Correct Answer: Pumping drug back into the intestinal lumen, lowering net absorption

Q6. Which formulation approach is commonly used to improve oral absorption of a highly lipophilic drug that undergoes extensive first-pass metabolism?

• Convert to a more crystalline polymorph
• Develop a lipid-based formulation to promote lymphatic uptake
• Increase tablet hardness to reduce dissolution
• Add antacid excipients to raise gastric pH

Correct Answer: Develop a lipid-based formulation to promote lymphatic uptake

Q7. Food effect: a high-fat meal most commonly alters bioavailability by which primary mechanisms?

• Reducing intestinal transit time and decreasing absorption
• Increasing bile secretion and solubilization of lipophilic drugs
• Lowering gastric pH uniformly and preventing dissolution
• Stimulating P-gp expression immediately after ingestion

Correct Answer: Increasing bile secretion and solubilization of lipophilic drugs

Q8. Which property of a salt form of a drug can most markedly change oral bioavailability?

• Melting point of the free base
• Dose equivalent of active moiety only
• Intrinsic solubility and dissolution rate of the chosen salt
• Polarity of the counterion with no effect on solubility

Correct Answer: Intrinsic solubility and dissolution rate of the chosen salt

Q9. Enterohepatic recycling affects plasma concentration–time profiles by causing:

• Single sharp peak with shorter Tmax
• Multiple peaks or prolonged terminal phase
• Complete prevention of first-pass metabolism
• Immediate renal elimination increase

Correct Answer: Multiple peaks or prolonged terminal phase

Q10. Which analytical/bioanalytical parameter is most directly used to quantify extent of systemic exposure and hence bioavailability?

• Tmax (time to maximum concentration)
• Cmax (maximum plasma concentration)
• AUC (area under the plasma concentration–time curve)
• Half-life (t1/2)

Correct Answer: AUC (area under the plasma concentration–time curve)

Q11. A drug exhibits precipitation in the intestinal lumen after passing from the stomach due to pH shift. This phenomenon primarily causes what type of absorption limitation?

• Permeability-limited absorption
• Dissolution-limited absorption due to solubility window
• Enzyme-mediated clearance increase
• Protein-binding driven sequestration

Correct Answer: Dissolution-limited absorption due to solubility window

Q12. Which excipient is most likely to inhibit intestinal efflux transporters and thus increase oral bioavailability of a substrate drug?

• Microcrystalline cellulose
• Polysorbate 80 (Tween 80)
• Lactose monohydrate
• Magnesium stearate at typical lubricant levels

Correct Answer: Polysorbate 80 (Tween 80)

Q13. High first-pass hepatic extraction is best characterized by which hepatic extraction ratio (E)?

• E ≈ 0.05
• E ≈ 0.3
• E ≈ 0.7
• E ≈ 0.001

Correct Answer: E ≈ 0.7

Q14. Which of the following will most likely increase intestinal absorption of a low-permeability (BCS class III) drug?

• Reducing contact time in the small intestine
• Co-administering a permeation enhancer that transiently opens tight junctions
• Formulating into a slowly dissolving matrix tablet
• Using a more crystalline polymorph to slow dissolution

Correct Answer: Co-administering a permeation enhancer that transiently opens tight junctions

Q15. Which physicochemical change caused by polymorphism can alter oral bioavailability?

• Change in molecular structure (constitutional isomerism)
• Change in crystal lattice energy affecting solubility
• Change in the elemental composition of the molecule
• Conversion to a different salt with new counterion

Correct Answer: Change in crystal lattice energy affecting solubility

Q16. Co-administration of an enzyme inducer (e.g., rifampicin) will most likely affect bioavailability by:

• Decreasing hepatic and/or intestinal metabolism, increasing AUC
• Increasing metabolic clearance, decreasing AUC
• Blocking P-gp mediated efflux to increase absorption
• Raising gastric pH to improve dissolution of acids

Correct Answer: Increasing metabolic clearance, decreasing AUC

Q17. Which measurement from an in vivo study indicates the rate of absorption most directly?

• AUC0–∞
• t1/2 (elimination half-life)
• Tmax
• Volume of distribution

Correct Answer: Tmax

Q18. Lymphatic transport of a drug reduces first-pass hepatic metabolism because:

• The drug is rapidly eliminated by renal filtration before hepatic contact
• Lymph drains directly into the systemic circulation bypassing portal vein and liver
• Lymph enhances hepatic uptake and metabolism
• Lymph contains enzymes that metabolize the drug extensively

Correct Answer: Lymph drains directly into the systemic circulation bypassing portal vein and liver

Q19. Which in vitro technique is most relevant to predict dissolution-limited bioavailability of an immediate-release tablet?

• Permeability assay using Caco-2 monolayers
• Dissolution testing under biorelevant media and conditions
• Microsomal stability assay for metabolic clearance
• Protein binding determination by equilibrium dialysis

Correct Answer: Dissolution testing under biorelevant media and conditions

Q20. Supersaturation and subsequent precipitation in the intestine influence absorption by:

• Maintaining constant dissolved drug concentration above solubility permanently
• Temporarily increasing dissolved concentration above equilibrium, potentially enhancing absorption if precipitation is delayed
• Eliminating the need for permeation across the epithelium
• Preventing any uptake due to formation of insoluble complexes only

Correct Answer: Temporarily increasing dissolved concentration above equilibrium, potentially enhancing absorption if precipitation is delayed

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