Preparation of suspensions MCQs With Answer

Introduction: The preparation of suspensions is a core topic in B.Pharm, covering formulation strategies, dispersion techniques, and stability control for insoluble drug particles in liquid media. This guide explores suspension formulation principles such as wetting and levigation, particle size reduction, flocculation versus deflocculation, rheology modification, use of suspending agents, preservatives, and quality tests (sedimentation volume, redispersibility, viscosity, and particle size distribution). Emphasis is placed on practical processing methods—milling, homogenization, and structured vehicles—and critical stability issues like creaming, caking, Ostwald ripening, and zeta potential. Keywords: preparation of suspensions, suspension formulation, wetting agents, flocculation, suspending agents, particle size. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the main purpose of a wetting agent in the preparation of suspensions?

• Increase particle size
• Reduce surface tension and displace air from particle surfaces
• Act as a preservative
• Increase the pH of the medium

Correct Answer: Reduce surface tension and displace air from particle surfaces

Q2. Which technique is commonly used for particle size reduction of insoluble drugs for suspensions?

• Spray drying
• Ball milling
• Lyophilization
• Distillation

Correct Answer: Ball milling

Q3. Flocculation in suspensions is primarily desirable because it:

• Leads to caking that cannot be redispersed
• Promotes formation of hard aggregates
• Results in rapid and reversible sedimentation with easy redispersion
• Prevents any sedimentation

Correct Answer: Results in rapid and reversible sedimentation with easy redispersion

Q4. Which parameter quantitatively describes the degree of settling of particles in a suspension?

• Viscosity index
• Redispersibility factor
• Sedimentation volume (F)
• Zeta potential

Correct Answer: Sedimentation volume (F)

Q5. According to Stokes’ law, which factor decreases sedimentation rate of suspended particles?

• Decrease in liquid viscosity
• Increase in particle radius
• Decrease in density difference between particle and medium
• Increase in gravitational acceleration

Correct Answer: Decrease in density difference between particle and medium

Q6. Which of the following is a commonly used suspending agent in oral suspensions?

• Sodium chloride
• Carboxymethyl cellulose (CMC)
• Sorbitol
• Hydrogen peroxide

Correct Answer: Carboxymethyl cellulose (CMC)

Q7. What is the role of a structured vehicle in suspension formulation?

• To chemically react with the active drug
• To form a viscous network that reduces particle settling
• To sterilize the formulation
• To lower the pH drastically

Correct Answer: To form a viscous network that reduces particle settling

Q8. Levigation is best described as:

• Removing water from a suspension
• Wetting and trituration of a powder with a small amount of liquid to reduce particle size
• A sterilization method for suspensions
• Adding preservatives to the formulation

Correct Answer: Wetting and trituration of a powder with a small amount of liquid to reduce particle size

Q9. Which surfactant is commonly used as a wetting agent for hydrophobic drug powders?

• Polysorbate 80 (Tween 80)
• Sodium chloride
• Paraben
• Citric acid

Correct Answer: Polysorbate 80 (Tween 80)

Q10. Zeta potential is an indicator of:

• Chemical degradation rate
• Electrostatic stability of dispersed particles
• Preservative efficacy
• Viscosity of the continuous phase

Correct Answer: Electrostatic stability of dispersed particles

Q11. Ostwald ripening in suspensions refers to:

• Formation of a crystalline shell on particles
• Growth of larger particles at the expense of smaller ones due to solubility differences
• Immediate precipitation of dissolved drug
• Microbial growth in the suspension

Correct Answer: Growth of larger particles at the expense of smaller ones due to solubility differences

Q12. Which test assesses how easily a sediment can be redispersed?

• Microbial limit test
• Redispersibility test
• Assay by HPLC
• pH meter reading

Correct Answer: Redispersibility test

Q13. Creaming differs from caking in that creaming is:

• Irreversible and prevents redispersion
• Reversible accumulation of particles at the top or bottom without hard packing
• A chemical decomposition process
• Another term for microbial spoilage

Correct Answer: Reversible accumulation of particles at the top or bottom without hard packing

Q14. Which preservative is commonly used in aqueous oral suspensions?

• Methylparaben
• Polyethylene glycol 4000
• Sodium benzoate at pH 10
• Glycerin

Correct Answer: Methylparaben

Q15. What effect does increasing the viscosity of the continuous phase have on sedimentation?

• Increases sedimentation rate
• No effect on sedimentation
• Decreases sedimentation rate
• Destroys the active drug

Correct Answer: Decreases sedimentation rate

Q16. Which process is most suitable to produce very fine submicron particles for suspensions?

• Wet milling (media milling)
• Simple mixing with spatula
• Freeze–thaw cycling
• Direct compression

Correct Answer: Wet milling (media milling)

Q17. A high negative zeta potential typically indicates:

• Strong tendency for particle aggregation
• Good electrostatic repulsion and dispersion stability
• Chemical instability of the drug
• High osmolarity of the medium

Correct Answer: Good electrostatic repulsion and dispersion stability

Q18. Which excipient can act both as a suspending agent and a thickener?

• Calcium chloride
• Xanthan gum
• Sodium hydroxide
• Isopropyl alcohol

Correct Answer: Xanthan gum

Q19. The primary reason for adjusting pH in a suspension formulation is to:

• Match container color
• Optimize drug solubility, stability, and preservative efficacy
• Increase particle density
• Reduce viscosity dramatically

Correct Answer: Optimize drug solubility, stability, and preservative efficacy

Q20. What is the effect of adding electrolytes to a suspension of charged particles?

• Increase zeta potential magnitude and enhance repulsion
• Compress the electrical double layer and may promote flocculation
• Always sterilize the suspension
• Convert suspension into an emulsion

Correct Answer: Compress the electrical double layer and may promote flocculation

Q21. Which quality control test measures the mechanical resistance of a suspension to flow?

• Viscosity measurement using a rheometer or viscometer
• pH measurement
• Assay by UV spectrophotometry
• Microbial culture

Correct Answer: Viscosity measurement using a rheometer or viscometer

Q22. Which milling technique uses high-velocity compressed gas to pulverize particles?

• Ball milling
• Jet milling (air milling)
• Mortar and pestle trituration
• Centrifugation

Correct Answer: Jet milling (air milling)

Q23. In preparing an oral suspension, why is antimicrobial preservation important?

• Preservatives enhance dissolution rate
• To prevent microbial contamination during storage and use
• They decrease viscosity for better pourability
• They neutralize the active drug

Correct Answer: To prevent microbial contamination during storage and use

Q24. Which of the following is a sign of physical instability in a suspension?

• Uniform color and smooth pour
• Formation of an irreversibly compact sediment (caking)
• Consistent particle size distribution over time
• Stable sedimentation volume with easy redispersion

Correct Answer: Formation of an irreversibly compact sediment (caking)

Q25. The term “redispersibility” refers to:

• The ability to sterilize a suspension by heating
• The capacity to resuspend settled particles uniformly with gentle shaking
• The conversion of suspension into solution
• The dissolution rate of the drug in water

Correct Answer: The capacity to resuspend settled particles uniformly with gentle shaking

Q26. Which analytical technique is used to determine particle size distribution in suspensions?

• Fourier-transform infrared spectroscopy (FTIR)
• Laser diffraction
• Gas chromatography
• Nitrogen adsorption only

Correct Answer: Laser diffraction

Q27. A deflocculated suspension is characterized by:

• Loose individual particles that settle slowly but form a hard cake
• Large flocs that settle fast but are easily redispersed
• Immediate chemical degradation
• No sedimentation at all

Correct Answer: Loose individual particles that settle slowly but form a hard cake

Q28. Which excipient would you choose to improve wettability of a highly hydrophobic powder?

• Hydrophobic oil blend
• Polysorbate 80 or other nonionic surfactant
• Magnesium stearate as added powder lubricant
• Calcium carbonate

Correct Answer: Polysorbate 80 or other nonionic surfactant

Q29. Which formulation approach helps prevent Ostwald ripening in suspensions?

• Use of co-solvents to greatly increase solubility of the drug
• Inclusion of low-solubility oils or polymers to reduce solubility differences
• Raising storage temperature
• Eliminating all surfactants

Correct Answer: Inclusion of low-solubility oils or polymers to reduce solubility differences

Q30. During scale-up of a suspension manufacturing process, which factor is most critical to maintain similar suspension quality?

• Color of the manufacturing vessel
• Hydrodynamic shear and energy input leading to comparable particle size and dispersion
• Changing the preservative at larger scale
• Reducing the mixing time to near zero

Correct Answer: Hydrodynamic shear and energy input leading to comparable particle size and dispersion

Download