Applications of cyclodextrins in formulation MCQs With Answer

Introduction: Cyclodextrins are cyclic oligosaccharides widely used in pharmaceutical formulation to improve drug solubility, stability, and bioavailability. Their unique hydrophobic cavity forms inclusion complexes with guest molecules, enabling enhanced dissolution rate, protection from degradation, taste masking, and controlled release. Common types include α-, β-, γ-cyclodextrins and derivatives like hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutylether-β-cyclodextrin (SBE-β-CD). Key formulation considerations include cavity size, complexation constant, phase-solubility behavior, and preparation methods (kneading, co-precipitation, freeze-drying, spray-drying). Understanding analytical tools (DSC, PXRD, FTIR) and safety/regulatory aspects is essential for B. Pharm students. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which structural feature of cyclodextrins primarily enables formation of inclusion complexes with hydrophobic drugs?

• A hydrophilic inner cavity
• A hydrophobic outer surface
• A hydrophobic inner cavity and hydrophilic outer surface
• Linear oligosaccharide chains

Correct Answer: A hydrophobic inner cavity and hydrophilic outer surface

Q2. Which cyclodextrin has the largest native cavity diameter and is best suited for larger drug molecules?

• α-Cyclodextrin
• β-Cyclodextrin
• γ-Cyclodextrin
• Maltooligosaccharide

Correct Answer: γ-Cyclodextrin

Q3. What is the main advantage of hydroxypropyl-β-cyclodextrin (HP-β-CD) over native β-cyclodextrin?

• Lower aqueous solubility
• Higher toxicity
• Improved aqueous solubility and reduced crystallinity
• Smaller cavity size

Correct Answer: Improved aqueous solubility and reduced crystallinity

Q4. In a phase-solubility diagram of drug–cyclodextrin systems, an A_L-type curve typically indicates what?

• Drug degrades in presence of cyclodextrin
• Linear increase in drug solubility with cyclodextrin concentration indicating 1:1 complexation
• Formation of higher-order insoluble complexes only
• No interaction between drug and cyclodextrin

Correct Answer: Linear increase in drug solubility with cyclodextrin concentration indicating 1:1 complexation

Q5. Which analytical technique is most useful to confirm loss of drug crystallinity after complexation with cyclodextrin?

• UV-Vis spectroscopy
• Powder X-ray diffraction (PXRD)
• pH measurement
• Karl Fischer titration

Correct Answer: Powder X-ray diffraction (PXRD)

Q6. Which preparation method often yields amorphous cyclodextrin complexes with improved dissolution: kneading, co-precipitation, spray-drying, or direct compression?

• Kneading
• Co-precipitation
• Spray-drying
• Direct compression

Correct Answer: Spray-drying

Q7. Complexation constant (K1:1) between drug and cyclodextrin indicates what property?

• The toxicity of the complex
• The strength of binding and stability of the 1:1 complex
• The particle size of precipitate
• The melting point of cyclodextrin

Correct Answer: The strength of binding and stability of the 1:1 complex

Q8. Which derivative is commonly used to enhance parenteral solubility of poorly soluble drugs due to favorable safety profile?

• Native β-cyclodextrin
• Hydroxypropyl-β-cyclodextrin (HP-β-CD)
• γ-Cyclodextrin
• α-Cyclodextrin

Correct Answer: Hydroxypropyl-β-cyclodextrin (HP-β-CD)

Q9. What is a common application of cyclodextrins in oral solid dosage forms?

• Increase drug volatility
• Mask bitter taste and enhance solubility
• Decrease tablet hardness
• Promote drug hydrolysis

Correct Answer: Mask bitter taste and enhance solubility

Q10. Which interaction primarily drives inclusion complex formation between cyclodextrin and guest molecules?

• Covalent bonding
• Hydrogen bonding only
• Hydrophobic interactions and van der Waals forces
• Electrostatic precipitation

Correct Answer: Hydrophobic interactions and van der Waals forces

Q11. SBE-β-CD (sulfobutylether-β-cyclodextrin) is particularly useful because it provides:

• Increased lipophilicity of drug
• Negative charge and enhanced aqueous solubility for parenteral use
• Reduced molecular weight
• Stronger covalent binding to drug

Correct Answer: Negative charge and enhanced aqueous solubility for parenteral use

Q12. Which method provides quantitative information about inclusion stoichiometry and binding constants in cyclodextrin complexes?

• Thermogravimetric analysis only
• Phase-solubility studies with slope analysis
• Simple visual inspection
• Colorimetry without concentration data

Correct Answer: Phase-solubility studies with slope analysis

Q13. Cyclodextrin complexation often improves chemical stability of drugs by:

• Increasing exposure to light
• Shielding labile functional groups inside the cavity
• Raising formulation pH drastically
• Forming covalent adducts that alter drug structure

Correct Answer: Shielding labile functional groups inside the cavity

Q14. Which is a limitation associated with using native β-cyclodextrin in high doses systemically?

• High renal clearance without toxicity
• Liver enzyme activation only
• Nephrotoxicity due to limited aqueous solubility and accumulation
• Excessive permeability enhancement causing overdose

Correct Answer: Nephrotoxicity due to limited aqueous solubility and accumulation

Q15. In taste-masking applications for oral liquids, cyclodextrins function by:

• Covalently modifying taste receptors
• Forming inclusion complexes that reduce free drug concentration at taste buds
• Lowering formulation pH to denature drug
• Increasing drug liberation rate in mouth

Correct Answer: Forming inclusion complexes that reduce free drug concentration at taste buds

Q16. Which experimental evidence supports inclusion complex formation rather than simple physical mixture?

• Unchanged melting point and PXRD pattern
• Shift or disappearance of drug melting endotherm in DSC and loss of sharp PXRD peaks
• Visible phase separation
• Identical FTIR spectra with no shifts

Correct Answer: Shift or disappearance of drug melting endotherm in DSC and loss of sharp PXRD peaks

Q17. How can cyclodextrins affect drug permeability across biological membranes?

• Always reduce permeability by complexation
• Never influence permeability
• Can increase apparent permeability by maintaining high free drug concentration or act as a barrier depending on system
• Cause irreversible membrane damage to improve drug flux

Correct Answer: Can increase apparent permeability by maintaining high free drug concentration or act as a barrier depending on system

Q18. Which formulation approach combines cyclodextrin complexation with polymeric carriers to achieve controlled release?

• Immediate-release tableting only
• Cyclodextrin–polymer matrix or inclusion complex-loaded hydrogels
• Simple aqueous dilution
• Direct intravenous bolus without carrier

Correct Answer: Cyclodextrin–polymer matrix or inclusion complex-loaded hydrogels

Q19. Stoichiometry of most simple drug–cyclodextrin inclusion complexes is commonly:

• 2:1 drug:cyclodextrin
• 1:2 drug:cyclodextrin
• 1:1 drug:cyclodextrin
• 3:1 drug:cyclodextrin

Correct Answer: 1:1 drug:cyclodextrin

Q20. Which cyclodextrin property is most critical when selecting for a hydrophobic BCS Class II drug formulation?

• Cavity size and compatibility with drug molecular volume
• Color of cyclodextrin powder
• Melting point of cyclodextrin
• Ability to form covalent bonds

Correct Answer: Cavity size and compatibility with drug molecular volume

Q21. Which drying method is preferred to preserve inclusion complex integrity while producing a dry powder with good flow?

• Oven drying at high temperature
• Spray-drying with optimized inlet temperature
• Open sun drying
• Lyophilization without cryoprotectant always

Correct Answer: Spray-drying with optimized inlet temperature

Q22. Which parameter from a phase-solubility study is directly used to calculate the apparent stability constant (K1:1)?

• Slope of the linear portion and intrinsic drug solubility
• Color change of solution
• Viscosity of formulation
• Dissolution medium pH only

Correct Answer: Slope of the linear portion and intrinsic drug solubility

Q23. Why are modified cyclodextrins often preferred over native ones in ocular formulations?

• Native cyclodextrins are always sterile and non-irritant
• Modified cyclodextrins like HP-β-CD have better solubility and lower irritation potential
• They form covalent links with ocular proteins
• They permanently open tight junctions

Correct Answer: Modified cyclodextrins like HP-β-CD have better solubility and lower irritation potential

Q24. Which phenomenon indicates formation of insoluble drug–cyclodextrin complex in phase-solubility profile?

• A_L-type linear increase
• B_S-type curve showing precipitation at higher cyclodextrin concentrations
• Complete absence of drug in solution at all concentrations
• Immediate gas evolution

Correct Answer: B_S-type curve showing precipitation at higher cyclodextrin concentrations

Q25. For improving volatile drug stability, cyclodextrin complexation primarily works by:

• Increasing vapor pressure
• Reducing headspace through inclusion complexation and lowering evaporation
• Reacting to form new volatile compounds
• Raising storage temperature

Correct Answer: Reducing headspace through inclusion complexation and lowering evaporation

Q26. Which in vitro technique can monitor changes in molecular environment of drug after complexation via shifts in characteristic peaks?

• FTIR spectroscopy
• Particle size analysis only
• pH titration
• Moisture content measurement only

Correct Answer: FTIR spectroscopy

Q27. How can cyclodextrins be used to reduce irritation in topical formulations?

• By increasing free drug concentration on skin surface
• By sequestering irritant molecules and releasing drug slowly at target site
• By chemically modifying skin proteins
• By raising formulation pH to extreme values

Correct Answer: By sequestering irritant molecules and releasing drug slowly at target site

Q28. Which statement about complexation efficiency (CE) is true?

• CE is independent of cyclodextrin concentration and gives direct measure of complexation tendency
• CE equals drug melting point
• CE determines color change on complexation
• CE is meaningless in formulation design

Correct Answer: CE is independent of cyclodextrin concentration and gives direct measure of complexation tendency

Q29. In nanoparticle formulations, cyclodextrins can aid drug loading by:

• Acting as covalent cross-linkers with polymers
• Solubilizing hydrophobic drug through inclusion and facilitating incorporation into nanoparticle matrix
• Preventing drug encapsulation entirely
• Degrading the polymeric carrier

Correct Answer: Solubilizing hydrophobic drug through inclusion and facilitating incorporation into nanoparticle matrix

Q30. Regulatory considerations for cyclodextrin use in formulations include assessment of:

• Only color and odor
• Toxicology, acceptable daily intake, route of administration, and impurity profile
• Only pH of final product
• Only the crystalline habit of cyclodextrin

Correct Answer: Toxicology, acceptable daily intake, route of administration, and impurity profile

Download