Suspensions – definition and classification MCQs With Answer

Suspensions – definition and classification MCQs With Answer

Pharmaceutical suspensions are biphasic, coarse dispersions containing insoluble solid particles dispersed in a liquid vehicle. For B. Pharm students, mastering the definition, classification, and key concepts—dispersed phase, dispersion medium, particle size (1–100 µm), sedimentation, Stoke’s law, zeta potential, DLVO theory, flocculated vs deflocculated systems, and routes (oral, topical, parenteral)—is essential. Understanding suspending agents, wetting agents, viscosity modifiers, structured vehicles, thixotropy, nanosuspensions, and “dry powders for reconstitution” ensures sound formulation and evaluation. Classification can be based on flocculation state, route, vehicle, particle size, and dosage form. These fundamentals directly impact stability, redispersibility, and therapeutic performance. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which best defines a pharmaceutical suspension?

• A homogeneous solution of a drug in a solvent
• A biphasic system of immiscible liquids stabilized by emulsifiers
• A two-phase system of insoluble solid particles dispersed in a liquid vehicle
• A gaseous dispersion of liquid droplets

Correct Answer: A two-phase system of insoluble solid particles dispersed in a liquid vehicle

Q2. The dispersed phase and dispersion medium in an oral aqueous suspension are respectively:

• Water and insoluble solid particles
• Insoluble solid particles and water
• Oil and water
• Water and oil

Correct Answer: Insoluble solid particles and water

Q3. The typical particle size range for coarse pharmaceutical suspensions is:

• 1–100 µm
• 1–100 nm
• 0.1–1 nm
• 0.1–0.5 mm

Correct Answer: 1–100 µm

Q4. Which classification distinguishes suspensions by their flocculation state?

• Oral vs parenteral
• Flocculated vs deflocculated
• Aqueous vs oily
• Ready-to-use vs dry powder for reconstitution

Correct Answer: Flocculated vs deflocculated

Q5. A key advantage of a flocculated suspension is:

• No sediment formation
• Rapid sedimentation with a loosely packed, easily redispersed sediment
• Very slow sedimentation with hard cake formation
• Permanent stability without agitation

Correct Answer: Rapid sedimentation with a loosely packed, easily redispersed sediment

Q6. Sedimentation volume (F) is defined as:

• Vo/Vu, where Vo is original volume and Vu is sediment volume
• Vu/Vo, where Vu is ultimate sediment volume and Vo is original volume
• Viscosity divided by density
• Particle size divided by zeta potential

Correct Answer: Vu/Vo, where Vu is ultimate sediment volume and Vo is original volume

Q7. According to Stoke’s law, sedimentation rate increases with:

• Decreasing particle diameter
• Increasing viscosity of the medium
• Increasing particle diameter and density difference
• Decreasing gravitational acceleration

Correct Answer: Increasing particle diameter and density difference

Q8. Controlled flocculation in suspensions can be achieved by:

• Adding only hydrophobic drugs
• Using electrolytes, polymers, or surfactants to adjust interparticle forces
• Increasing particle hardness
• Decreasing temperature to zero

Correct Answer: Using electrolytes, polymers, or surfactants to adjust interparticle forces

Q9. Zeta potential primarily reflects:

• Particle size distribution
• Surface charge affecting particulate repulsion and flocculation
• Viscosity of the vehicle
• Drug solubility

Correct Answer: Surface charge affecting particulate repulsion and flocculation

Q10. DLVO theory explains the balance between:

• Viscosity and density
• Gravitational and buoyant forces
• Van der Waals attraction and electrostatic repulsion
• Solubility and permeability

Correct Answer: Van der Waals attraction and electrostatic repulsion

Q11. Classification by route of administration includes:

• Flocculated and deflocculated
• Colloidal and coarse
• Oral, topical, ophthalmic, parenteral
• Monodisperse and polydisperse

Correct Answer: Oral, topical, ophthalmic, parenteral

Q12. Which is NOT a suspension?

• Magnesium hydroxide mixture
• Calamine lotion
• Paracetamol solution
• Procaine penicillin G intramuscular depot

Correct Answer: Paracetamol solution

Q13. Nanosuspensions are best described as:

• Solutions of drugs in nanocarriers
• Submicron pure drug particles dispersed in a liquid and stabilized by surfactants/polymers
• O/W emulsions with nanodroplets
• Gels with nanofibers

Correct Answer: Submicron pure drug particles dispersed in a liquid and stabilized by surfactants/polymers

Q14. Suspensions differ from emulsions primarily by having:

• Two immiscible liquid phases
• Solid dispersed phase in a liquid medium
• No need for stabilizers
• Smaller particle size than colloids

Correct Answer: Solid dispersed phase in a liquid medium

Q15. Classification by vehicle distinguishes:

• Aqueous suspensions and oily suspensions
• Isotonic and hypertonic
• Buffered and unbuffered
• Sterile and non-sterile

Correct Answer: Aqueous suspensions and oily suspensions

Q16. Which statement about deflocculated suspensions is TRUE?

• They sediment rapidly but redisperse easily
• They show high sedimentation volume (F ≈ 1)
• They sediment slowly but can form a compact cake
• They cannot contain electrolytes

Correct Answer: They sediment slowly but can form a compact cake

Q17. A common flocculating agent acting via electrolyte compression of the double layer is:

• Sodium chloride
• Sodium carboxymethylcellulose
• Sorbitol
• Propylene glycol

Correct Answer: Sodium chloride

Q18. In classification by dosage form, “dry powder for reconstitution” suspensions are designed to:

• Be administered intravenously without dilution
• Improve stability by reconstituting with water at dispensing
• Eliminate the need for suspending agents
• Produce an emulsion upon mixing

Correct Answer: Improve stability by reconstituting with water at dispensing

Q19. An example of a suspending agent used to create a structured vehicle is:

• Sodium lauryl sulfate
• Carbomer or xanthan gum
• Ethanol
• Menthol

Correct Answer: Carbomer or xanthan gum

Q20. Wetting agents in suspensions primarily:

• Increase particle size
• Reduce interfacial tension and contact angle to aid dispersion of hydrophobic powders
• Act as preservatives
• Increase density of particles

Correct Answer: Reduce interfacial tension and contact angle to aid dispersion of hydrophobic powders

Q21. Which classification is based on particle size?

• Coarse suspensions vs colloids vs nanosuspensions
• Oral vs topical vs parenteral
• Buffered vs unbuffered
• Sweetened vs unsweetened

Correct Answer: Coarse suspensions vs colloids vs nanosuspensions

Q22. For intravenous suspensions, a critical requirement is:

• Particle size typically below 5 µm with sterility and low endotoxin
• High sedimentation volume
• Use of oily vehicle
• Absence of any surfactant

Correct Answer: Particle size typically below 5 µm with sterility and low endotoxin

Q23. Classification by redispersibility would rank best to worst as:

• Deflocculated > flocculated
• Flocculated > deflocculated
• Colloidal > nanosuspension
• Oily > aqueous

Correct Answer: Flocculated > deflocculated

Q24. A sedimentation volume (F) close to 1 in a suspension usually indicates:

• Poor flocculation and severe caking
• High degree of flocculation or structured vehicle maintaining volume
• Complete dissolution of drug
• Inadequate viscosity

Correct Answer: High degree of flocculation or structured vehicle maintaining volume

Q25. Classification by therapeutic use would include:

• Antacid suspensions, antibiotic suspensions, corticosteroid suspensions
• Isotonic and hypertonic suspensions
• Hydrophilic and lipophilic suspensions
• Sugar-free and sugar-containing suspensions

Correct Answer: Antacid suspensions, antibiotic suspensions, corticosteroid suspensions

Q26. A structured vehicle desirable for suspensions often exhibits:

• Dilatant behavior
• Pseudoplastic flow with thixotropy
• Newtonian flow
• Elastic solid behavior only

Correct Answer: Pseudoplastic flow with thixotropy

Q27. Which test most directly evaluates redispersibility?

• pH measurement
• Number of gentle inversions needed to resuspend after storage
• Assay by HPLC
• Surface tension measurement

Correct Answer: Number of gentle inversions needed to resuspend after storage

Q28. In classification by stability mechanism, a system stabilized mainly by polymer “bridging” is:

• Electrostatically stabilized deflocculated system
• Bridging-flocculated system
• Brownian motion–stabilized colloid
• Micellar solution

Correct Answer: Bridging-flocculated system

Q29. Which excipient is primarily a wetting agent rather than a suspending agent?

• Polysorbate 80
• Microcrystalline cellulose
• Xanthan gum
• Bentonite

Correct Answer: Polysorbate 80

Q30. Oily depot suspensions for intramuscular injection are commonly classified as:

• Oily, parenteral, flocculated depot formulations
• Aqueous, oral, deflocculated formulations
• Colloidal, ophthalmic emulsions
• Solutions with solubilizers

Correct Answer: Oily, parenteral, flocculated depot formulations

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