Semisolid excipients and their applications MCQs With Answer

Semisolid excipients are key components in topical formulations such as ointments, creams, and gels, influencing stability, rheology, drug release, and skin penetration. For B.Pharm students, mastering excipient classification — including emollients, emulsifiers, humectants, thickeners, preservatives, and penetration enhancers — is essential for formulation design and quality control. Understanding physicochemical properties, compatibility with active pharmaceutical ingredients, and impact on drug delivery and patient acceptability prepares you for practical compounding and regulatory evaluation. This concise MCQ set focuses on semisolid excipients, their functions, selection criteria, and analytical considerations to strengthen formulation knowledge and exam readiness. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which of the following is an example of an oleaginous (hydrocarbon) ointment base?

• White petrolatum
• Hydrophilic ointment
• PEG 400
• Carbopol gel

Correct Answer: White petrolatum

Q2. Which excipient primarily acts to reduce surface tension and stabilize oil-in-water emulsions?

• Humectant
• Emulsifier
• Preservative
• Gelling agent

Correct Answer: Emulsifier

Q3. The Hydrophilic-Lipophilic Balance (HLB) value is most useful for selecting which excipient?

• Thickening agent
• Emulsifier
• Preservative
• Penetration enhancer

Correct Answer: Emulsifier

Q4. Which semisolid excipient is commonly used as a humectant to retain moisture in formulations?

• Paraffin wax
• Glycerin
• Stearic acid
• Lanolin alcohol

Correct Answer: Glycerin

Q5. Carbopol polymers are used in semisolid formulations primarily as:

• Preservatives
• Penetration enhancers
• Rheology modifiers (gelling agents)
• Emollients

Correct Answer: Rheology modifiers (gelling agents)

Q6. Which property of an ointment base most directly affects topical drug release rate?

• Color
• Occlusiveness
• Manufacturer brand
• Container shape

Correct Answer: Occlusiveness

Q7. Which preservative is commonly used in aqueous semisolid preparations but may cause contact sensitivity?

• Methylparaben
• Propylene glycol
• Mineral oil
• Carbomer

Correct Answer: Methylparaben

Q8. A water-removable (cream) base is best described as:

• Completely hydrophobic and non-washable
• An oil-in-water emulsion that is washable
• Pure polyethylene glycol without water
• A gas-filled aerosol foam

Correct Answer: An oil-in-water emulsion that is washable

Q9. Which analytical test assesses the ease with which a semisolid spreads on the skin?

• Spreadability test
• pH measurement
• Viscosity by viscometer only
• Loss on drying

Correct Answer: Spreadability test

Q10. Which excipient can function both as a solvent and a penetration enhancer in topical gels?

• Stearyl alcohol
• Propylene glycol
• Stearic acid
• White petrolatum

Correct Answer: Propylene glycol

Q11. Which class of semisolid bases will generally provide the highest degree of skin occlusion?

• Water-soluble bases (PEG bases)
• Oleaginous (hydrocarbon) bases
• Oil-in-water creams
• Gels

Correct Answer: Oleaginous (hydrocarbon) bases

Q12. Which rheological behavior is typically desirable for a topical cream to ensure easy application and stay-on-skin properties?

• Newtonian flow with low viscosity
• Thixotropic pseudoplastic behavior
• Dilational viscoelasticity only
• Bingham plastic with no yield stress

Correct Answer: Thixotropic pseudoplastic behavior

Q13. Which test is most appropriate to evaluate the microbial quality of semisolid pharmaceutical products?

• Emulsification index
• Total aerobic microbial count and absence of specified pathogens
• Melting point determination
• Fortification drying test

Correct Answer: Total aerobic microbial count and absence of specified pathogens

Q14. An emulsion is considered physically unstable when it shows:

• Constant pH
• Phase separation or creaming
• Consistent viscosity over time
• Uniform color

Correct Answer: Phase separation or creaming

Q15. Which excipient is commonly used to neutralize carbopol and produce gelation?

• Sodium hydroxide
• Mineral oil
• Propylene glycol
• Lanolin

Correct Answer: Sodium hydroxide

Q16. Which factor most influences the choice of semisolid excipient for a hydrophilic drug intended for topical delivery?

• Drug color
• Drug solubility in the base
• Company logo
• Ambient noise during manufacturing

Correct Answer: Drug solubility in the base

Q17. Which of the following is NOT typically a purpose of adding preservatives to semisolid formulations?

• Prevent microbial growth
• Enhance fragrance longevity
• Maintain product safety during use
• Protect against spoilage from contaminants

Correct Answer: Enhance fragrance longevity

Q18. Which excipient would you choose to prepare a water-soluble ointment base for a hydrophilic active?

• White petrolatum
• Polyethylene glycol (PEG) base
• Liquid paraffin
• Beeswax

Correct Answer: Polyethylene glycol (PEG) base

Q19. Which penetration enhancer acts by disrupting stratum corneum lipids to increase drug permeation?

• Humectants like glycerin
• Fatty alcohols like oleyl alcohol
• Preservatives like methylparaben
• Hydrophilic polymers like carbopol

Correct Answer: Fatty alcohols like oleyl alcohol

Q20. In emulsion stability, a small mean globule size generally leads to:

• Increased creaming and faster separation
• Improved physical stability and reduced coalescence
• Higher microbial contamination risk
• Lower viscosity regardless of composition

Correct Answer: Improved physical stability and reduced coalescence

Q21. Which excipient is most likely to cause irritation or allergic contact dermatitis in patients sensitive to wool-derived products?

• Lanolin
• Glycerin
• Dimethyl sulfoxide (DMSO)
• Carbomer

Correct Answer: Lanolin

Q22. For quality control of creams, which parameter assesses water content and potential for microbial growth?

• pH measurement
• Water activity (aw)
• Thermal conductivity
• Colorimetry

Correct Answer: Water activity (aw)

Q23. Which gelling agent is of natural origin and commonly used in topical gels for its biocompatibility?

• Carbopol
• Methylcellulose
• Agar or tragacanth
• Sodium lauryl sulfate

Correct Answer: Agar or tragacanth

Q24. Which excipient property is most critical when formulating semisolids with acid- or base-sensitive drugs?

• Odor profile
• Chemical compatibility and pH stability
• Color matching
• Label design

Correct Answer: Chemical compatibility and pH stability

Q25. Which method is commonly used to evaluate the rheological properties of semisolids?

• UV-visible spectrophotometry
• Viscometry or rheometry
• Mass spectrometry
• Gas chromatography

Correct Answer: Viscometry or rheometry

Q26. Which preservative system is preferable for multi-dose aqueous semisolid products to cover a broad microbial spectrum?

• Single alcohol only
• Combination of parabens or parabens plus organic acids
• Pure water without additives
• High concentration of humectants only

Correct Answer: Combination of parabens or parabens plus organic acids

Q27. A semisolid intended for acne treatment contains benzoyl peroxide. Which excipient incompatibility should be avoided?

• Reducing agents that decompose benzoyl peroxide
• Non-ionic emulsifiers
• Water
• Glycerin as humectant

Correct Answer: Reducing agents that decompose benzoyl peroxide

Q28. Which characterization technique helps identify the microstructure and internal phase of emulsions in semisolids?

• Optical or electron microscopy
• pH indicator strips
• Mass per unit area measurement
• Thermal gravimetric analysis only

Correct Answer: Optical or electron microscopy

Q29. Which statement about water-in-oil (w/o) versus oil-in-water (o/w) semisolid bases is correct?

• o/w creams are more occlusive than w/o bases
• w/o bases tend to be more occlusive and better for dry skin
• w/o bases cannot incorporate water
• o/w bases cannot be washed off with water

Correct Answer: w/o bases tend to be more occlusive and better for dry skin

Q30. When formulating semisolids with heat-labile actives, which manufacturing consideration is most important?

• Use of high-temperature homogenization exclusively
• Minimizing exposure to elevated temperatures and using cold or low-temperature processes
• Adding fragrances at the beginning of heating
• Using metal containers that increase heat transfer

Correct Answer: Minimizing exposure to elevated temperatures and using cold or low-temperature processes

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