Methods to enhance dissolution rate and bioavailability of poorly soluble drugs MCQs With Answer

Introduction

Improving the dissolution rate and bioavailability of poorly soluble drugs is a core challenge in pharmaceutics. B. Pharm students must understand solubility enhancement strategies such as particle size reduction, solid dispersions, amorphous conversion, salt formation, cyclodextrin complexation, surfactants, lipid-based formulations (SEDDS/SMEDDS), and nanotechnology. Key concepts include BCS classification, wettability, dissolution testing, permeability interplay, and in vitro–in vivo correlation (IVIVC). Analytical methods like DSC, XRPD, SEM and dissolution apparatus are essential to characterize formulations. Mastery of these approaches supports rational selection of techniques to enhance oral absorption and therapeutic performance. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which BCS class mainly requires formulation strategies to enhance solubility and dissolution rate?

• Class I: High solubility, high permeability
• Class II: Low solubility, high permeability
• Class III: High solubility, low permeability
• Class IV: Low solubility, low permeability

Correct Answer: Class II: Low solubility, high permeability

Q2. Which technique primarily increases surface area to improve dissolution rate?

• Salt formation
• Particle size reduction (micronization/nanonization)
• Cyclodextrin complexation
• pH modification

Correct Answer: Particle size reduction (micronization/nanonization)

Q3. Solid dispersions enhance dissolution mainly by which mechanism?

• Forming a crystalline stable matrix
• Increasing drug crystallinity to reduce solubility
• Stabilizing the drug in an amorphous, higher-energy state dispersed in a polymer
• Decreasing wettability of drug particles

Correct Answer: Stabilizing the drug in an amorphous, higher-energy state dispersed in a polymer

Q4. Which polymer is commonly used as a hydrophilic carrier in solid dispersions?

• Polylactic acid (PLA)
• Polyvinylpyrrolidone (PVP)
• Polystyrene
• Polycaprolactone (PCL)

Correct Answer: Polyvinylpyrrolidone (PVP)

Q5. Cyclodextrin complexation improves solubility by which primary mechanism?

• Forming covalent bonds with drug molecules
• Encapsulating the lipophilic moiety of the drug in a hydrophobic cavity
• Reducing particle size to submicron range
• Changing drug pKa permanently

Correct Answer: Encapsulating the lipophilic moiety of the drug in a hydrophobic cavity

Q6. Which lipid-based system forms micro- or nano-emulsions in GI fluids to enhance oral absorption?

• Matrix tablets
• Sustained-release pellets
• Self-emulsifying drug delivery systems (SEDDS/SMEDDS)
• Immediate-release sugar-coated tablets

Correct Answer: Self-emulsifying drug delivery systems (SEDDS/SMEDDS)

Q7. Which technique converts crystalline drug into amorphous form to increase apparent solubility?

• Hot-melt extrusion
• Cooling crystallization
• Salt crystallization
• Recrystallization from a solvent

Correct Answer: Hot-melt extrusion

Q8. Which of the following surfactant roles improves dissolution?

• Decreasing drug permeability across membranes
• Enhancing wettability and solubilization of drug molecules
• Inducing crystallization of amorphous drug
• Increasing particle aggregation

Correct Answer: Enhancing wettability and solubilization of drug molecules

Q9. In vitro–in vivo correlation (IVIVC) is most useful for predicting:

• Tablet hardness from polymer chemistry
• Clinical bioavailability from dissolution profiles
• Sterility of parenteral formulations
• Chemical synthesis yield

Correct Answer: Clinical bioavailability from dissolution profiles

Q10. Which analytical technique distinguishes crystalline and amorphous drug forms?

• UV–Vis spectroscopy
• X-ray powder diffraction (XRPD)
• pH titration
• Karl Fischer titration

Correct Answer: X-ray powder diffraction (XRPD)

Q11. Salt formation improves solubility by:

• Converting drug to a more lipophilic form
• Increasing ionic form and aqueous solubility for ionizable drugs
• Creating a polymer-drug matrix
• Increasing melting point of the drug

Correct Answer: Increasing ionic form and aqueous solubility for ionizable drugs

Q12. Which parameter most directly influences dissolution rate according to the Noyes–Whitney equation?

• Boiling point of the solvent
• Surface area of the drug particle
• Drug color
• Tablet embossing

Correct Answer: Surface area of the drug particle

Q13. Spray drying is commonly used to prepare which improved-solubility form?

• Crystalline large particles
• Amorphous dispersions with polymer carriers
• Metallic salts
• Solid lipids only

Correct Answer: Amorphous dispersions with polymer carriers

Q14. Which statement about nanosuspensions is true?

• Nanosuspensions decrease dissolution rate due to aggregation
• Nanosuspensions improve dissolution by increasing surface area and saturation solubility
• Nanosuspensions always eliminate the need for stabilizers
• Nanosuspensions are only used for parenteral steroids

Correct Answer: Nanosuspensions improve dissolution by increasing surface area and saturation solubility

Q15. Which excipient acts as a precipitation inhibitor in supersaturating formulations?

• Hydroxypropyl methylcellulose (HPMC)
• Sodium chloride
• Calcium carbonate
• Talc

Correct Answer: Hydroxypropyl methylcellulose (HPMC)

Q16. Which dissolution apparatus is commonly used for immediate-release oral dosage forms?

• USP Apparatus I (Basket) and II (Paddle)
• Reverse osmosis unit
• Gas chromatography system
• High-performance liquid chromatography

Correct Answer: USP Apparatus I (Basket) and II (Paddle)

Q17. Co-crystals improve solubility by:

• Altering drug molecular packing via a neutral co-former
• Forming ionic salts only
• Degrading the drug chemically
• Polymerizing the drug

Correct Answer: Altering drug molecular packing via a neutral co-former

Q18. Which property of a drug most limits oral bioavailability besides solubility?

• Melting point only
• Permeability across the intestinal membrane
• Color of the dosage form
• Tablet size engraving

Correct Answer: Permeability across the intestinal membrane

Q19. Which method assesses particle morphology and surface characteristics?

• Differential scanning calorimetry (DSC)
• Scanning electron microscopy (SEM)
• pH meter
• Optical rotation

Correct Answer: Scanning electron microscopy (SEM)

Q20. Which approach increases wettability of hydrophobic drug particles?

• Adding hydrophobic waxes
• Using surfactants or wetting agents
• Decreasing dissolution medium volume only
• Coating with enteric polymers

Correct Answer: Using surfactants or wetting agents

Q21. Which polymer is commonly used in hot-melt extrusion to form amorphous solid dispersions?

• PVC (polyvinyl chloride)
• PVP-VA (copolymer of vinylpyrrolidone and vinyl acetate)
• Natural rubber
• Polytetrafluoroethylene (PTFE)

Correct Answer: PVP-VA (copolymer of vinylpyrrolidone and vinyl acetate)

Q22. Which factor can decrease dissolution rate of a formulated tablet?

• Reduced crystallinity
• Increased tablet hardness and decreased porosity
• Use of hydrophilic disintegrants
• Particle size reduction

Correct Answer: Increased tablet hardness and decreased porosity

Q23. Which statement best describes supersaturation in oral formulations?

• A state where drug concentration is below equilibrium solubility
• A metastable state with drug concentration above equilibrium solubility that can enhance absorption
• A permanent chemical modification of drug structure
• An indicator of drug degradation

Correct Answer: A metastable state with drug concentration above equilibrium solubility that can enhance absorption

Q24. Which method is used to measure zeta potential in nanoparticle systems?

• Dynamic light scattering (DLS) with electrophoretic mobility
• Thermogravimetric analysis (TGA)
• UV–Vis spectroscopy alone
• pH titration

Correct Answer: Dynamic light scattering (DLS) with electrophoretic mobility

Q25. Which excipient class is useful to form micelles and increase solubilization of lipophilic drugs?

• Hydrophobic fillers
• Surfactants (e.g., polysorbates)
• Non-ionic dyes
• Inert glass beads

Correct Answer: Surfactants (e.g., polysorbates)

Q26. Hot-melt extrusion advantages include:

• Use of large amounts of organic solvent
• Continuous processing and solvent-free production of solid dispersions
• Generation of highly crystalline drug formulations only
• MUST be performed at cryogenic temperatures

Correct Answer: Continuous processing and solvent-free production of solid dispersions

Q27. Which in vitro test is most relevant to assess dissolution improvement for a weakly basic drug?

• Dissolution in a single neutral pH only
• pH-gradient dissolution to simulate GI transit
• Gas permeability test
• Melting point determination

Correct Answer: pH-gradient dissolution to simulate GI transit

Q28. Which strategy reduces recrystallization of amorphous drug from supersaturated solution?

• Omitting polymers
• Including precipitation inhibitors like polymers or surfactants
• Heating the formulation during dissolution
• Using only crystalline drug forms

Correct Answer: Including precipitation inhibitors like polymers or surfactants

Q29. Which formulation approach can enhance lymphatic uptake and bypass first-pass metabolism?

• Enteric-coated immediate-release tablet
• Lipid-based formulations that promote chylomicron association
• Simple sugar granulation
• Adding high amounts of insoluble fillers

Correct Answer: Lipid-based formulations that promote chylomicron association

Q30. Which characterization technique determines thermal transitions and compatibility in drug–polymer systems?

• Gas chromatography
• Differential scanning calorimetry (DSC)
• Conductivity meter
• Polarimetry

Correct Answer: Differential scanning calorimetry (DSC)

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