Pharmaceutical dispersions: suspensions MCQs With Answer

Pharmaceutical dispersions: suspensions MCQs With Answer

Suspensions are central to Modern Pharmaceutics (MPH 103T) because they combine interfacial science, rheology, and formulation design to create stable, patient-friendly dosage forms. This quiz targets advanced understanding of preformulation challenges (wetting, particle size control), physical stability (flocculation vs. deflocculation, caking), rheological optimization (pseudoplasticity and thixotropy), and evaluation metrics (sedimentation volume, degree of flocculation, redispersibility). You will also encounter practical choices of excipients—flocculating agents, wetting agents, and suspending polymers—as well as mechanistic concepts like zeta potential, DLVO theory, and Ostwald ripening. Designed for M. Pharm students, these 20 MCQs blend theory with formulation strategy to strengthen problem-solving skills for both oral and parenteral suspensions.

Q1. In Stokes’ law-governed settling, halving the particle radius will change the sedimentation velocity by which factor (all else constant)?

• It will decrease twofold
• It will decrease fourfold
• It will decrease eightfold
• It will not change

Correct Answer: It will decrease fourfold

Q2. Which statement best distinguishes a flocculated from a deflocculated suspension?

• Flocculated suspensions settle slowly and form hard cake
• Deflocculated suspensions settle rapidly but are easily redispersed
• Flocculated suspensions settle rapidly but do not form a hard cake
• Deflocculated suspensions are always more viscous

Correct Answer: Flocculated suspensions settle rapidly but do not form a hard cake

Q3. Sedimentation volume (F) in a suspension is defined as:

• Volume of solids/total volume at time zero
• Ultimate volume of sediment (Vu) divided by original suspension volume (Vo)
• Weight of sediment/weight of dispersed phase
• Viscosity of continuous phase/viscosity of dispersed phase

Correct Answer: Ultimate volume of sediment (Vu) divided by original suspension volume (Vo)

Q4. The degree of flocculation (β) is most appropriately given by:

• β = Vo/Vu
• β = F/F∞
• β = η/ρ
• β = g/9η

Correct Answer: β = F/F∞

Q5. A classic electrolyte used to induce controlled flocculation in bismuth subnitrate suspensions is:

• Sodium citrate
• Glycerin
• PVP K30
• Sorbitol

Correct Answer: Sodium citrate

Q6. The most appropriate wetting agent for a hydrophobic drug in an oral pediatric suspension is:

• Polysorbate 80
• Sodium lauryl sulfate
• Benzalkonium chloride
• Span 80

Correct Answer: Polysorbate 80

Q7. The ideal rheological behavior for an oral suspension intended for good pourability and redispersion is:

• Newtonian flow with no hysteresis
• Dilatant flow
• Pseudoplastic flow with thixotropy
• Bingham plastic without thixotropy

Correct Answer: Pseudoplastic flow with thixotropy

Q8. With respect to zeta potential, controlled flocculation in aqueous suspensions is promoted by:

• Increasing the magnitude of zeta potential beyond ±40 mV
• Reducing the magnitude of zeta potential toward zero using electrolytes
• Only increasing vehicle viscosity without changing surface charge
• Coating particles with nonionic polymer to maximize steric repulsion

Correct Answer: Reducing the magnitude of zeta potential toward zero using electrolytes

Q9. A practical strategy to minimize Ostwald ripening in suspensions/nanosuspensions is to:

• Increase temperature cycling during storage
• Use adsorbing polymers (e.g., PVP, HPMC) for steric stabilization
• Use only high-HLB surfactants without polymers
• Decrease vehicle viscosity

Correct Answer: Use adsorbing polymers (e.g., PVP, HPMC) for steric stabilization

Q10. The best overall approach to prevent caking in a suspension is to:

• Reduce dispersed phase concentration as much as possible
• Form a deflocculated system with very fine particles
• Use controlled flocculation together with a structured vehicle
• Increase preservative concentration

Correct Answer: Use controlled flocculation together with a structured vehicle

Q11. To minimize grittiness and improve mouthfeel, the recommended median particle size for oral suspensions is approximately:

• 0.05–0.1 μm
• 1–5 μm
• 20–50 μm
• 100–250 μm

Correct Answer: 1–5 μm

Q12. On a rheogram, thixotropy in a suspension is indicated by:

• A straight line through the origin
• An increase in viscosity with shear rate
• A hysteresis loop between the up-curve and down-curve
• No change in viscosity over time

Correct Answer: A hysteresis loop between the up-curve and down-curve

Q13. For wetting hydrophobic powders in aqueous suspensions, the most suitable HLB range of nonionic surfactants is:

• 3–6
• 7–9
• 10–12
• 15–18

Correct Answer: 7–9

Q14. In nanosuspension stabilization using nonionic polymers such as PVP or HPMC, the dominant mechanism is:

• Electrostatic stabilization
• Steric stabilization
• Hydrodynamic stabilization
• Osmotic stabilization only

Correct Answer: Steric stabilization

Q15. The redispersibility test for suspensions primarily evaluates:

• The chemical stability of the drug
• The ease with which sediment can be uniformly resuspended after storage
• The potency of the preservative system
• The dissolution rate of the dispersed drug

Correct Answer: The ease with which sediment can be uniformly resuspended after storage

Q16. Syringeability and injectability of parenteral suspensions are most influenced by:

• Flavoring agents and sweeteners
• Particle size distribution and dispersed phase concentration
• Colorants
• Buffer capacity

Correct Answer: Particle size distribution and dispersed phase concentration

Q17. According to DLVO theory, increasing the electrolyte concentration in a suspension generally:

• Expands the diffuse double layer and increases repulsion
• Compresses the double layer and decreases zeta potential
• Increases Brownian motion and prevents collisions
• Eliminates van der Waals attraction

Correct Answer: Compresses the double layer and decreases zeta potential

Q18. Sodium carboxymethyl cellulose (NaCMC) in suspensions primarily functions as a:

• Non-aqueous co-solvent
• Hydrophilic colloid providing pseudoplastic viscosity and a structured vehicle
• Primary flocculant via charge neutralization
• Crystal habit modifier only

Correct Answer: Hydrophilic colloid providing pseudoplastic viscosity and a structured vehicle

Q19. A sedimentation volume (F) greater than 1 in a suspension most often indicates:

• Severe caking due to compression
• A flocculated system with expanded sediment network
• A highly deflocculated system
• Creaming rather than sedimentation

Correct Answer: A flocculated system with expanded sediment network

Q20. For efficient wetting of hydrophobic drug particles in water, the contact angle (θ) should be:

• Less than 90°
• Equal to 90°
• Greater than 90°
• Independent of the solid surface properties

Correct Answer: Less than 90°

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