Preparation of pastes MCQs With Answer

Preparation of pastes MCQs With Answer is a focused study aid for B.Pharm students aiming to master paste formulation, excipient selection, and practical manufacturing steps. This resource highlights levigation, incorporation techniques, choice of vehicles and absorbents (zinc oxide, kaolin, starch), rheology concepts (plastic flow, thixotropy), stability issues, preservatives, and quality control tests. Emphasis is on real-world formulation challenges—wetting and levigating agents, heating methods, particle size reduction, packaging, and regulatory considerations—so students build problem-solving skills for topical semisolid preparations. Answers include concise explanations and references to pharmaceutics principles for targeted revision. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What primarily distinguishes a paste from an ointment?

• Higher liquid content and low consistency
• Higher proportion of finely divided solids and stiff consistency
• Use of volatile solvents only
• Requirement for sterility

Correct Answer: Higher proportion of finely divided solids and stiff consistency

Q2. Which technique is most commonly used to reduce particle size of solids during paste preparation?

• Sublimation
• Levigation
• Centrifugation
• Lyophilization

Correct Answer: Levigation

Q3. What is the main role of a levigating agent in paste preparation?

• To sterilize the paste
• To act as a preservative
• To wet and disperse insoluble solids, facilitating particle size reduction
• To increase the melting point of the base

Correct Answer: To wet and disperse insoluble solids, facilitating particle size reduction

Q4. Which of the following is commonly used as an absorbent or stiffening agent in pastes?

• Sorbitol
• Zinc oxide
• Polysorbate 80
• Sodium chloride

Correct Answer: Zinc oxide

Q5. The rheological behavior most characteristic of many pastes is:

• Newtonian flow
• Plastic flow with a yield value
• Ideal elastic solid behavior
• Perfectly viscous flow

Correct Answer: Plastic flow with a yield value

Q6. Thixotropy in pastes refers to:

• Increase in viscosity with time under shear
• Permanent solidification over time
• Time-dependent decrease in viscosity on standing after shear
• Instantaneous crystallization of the base

Correct Answer: Time-dependent decrease in viscosity on standing after shear

Q7. Which levigating agent is suitable for wetting hydrophilic powders?

• Glycerin
• Liquid paraffin
• Mineral oil
• Petrolatum

Correct Answer: Glycerin

Q8. For water-containing pastes, why are preservatives important?

• They increase viscosity
• They act as levigating agents
• They prevent microbial growth and spoilage
• They make the paste non-greasy

Correct Answer: They prevent microbial growth and spoilage

Q9. Which of the following is a common instability observed in pastes where liquid separates from the solid matrix?

• Crystallization
• Syneresis or bleeding
• Sublimation
• Polymerization

Correct Answer: Syneresis or bleeding

Q10. Which packaging is preferred to minimize contamination and exposure for topical pastes?

• Open wide-mouth jars only
• Collapsible metal or plastic tubes
• Glass ampoules requiring breakage
• Unsealed plastic bags

Correct Answer: Collapsible metal or plastic tubes

Q11. What is the primary objective of particle size reduction in paste formulations?

• To decrease drug potency
• To improve homogeneity, texture and potentially percutaneous absorption
• To increase odor
• To induce chemical degradation

Correct Answer: To improve homogeneity, texture and potentially percutaneous absorption

Q12. Which excipient acts as a stiffening and protective agent and also provides soothing properties when included in pastes?

• Propylene glycol
• Kaolin
• Isopropyl myristate
• Sodium lauryl sulfate

Correct Answer: Kaolin

Q13. When preparing a water-in-oil paste containing discrete aqueous droplets, which additive is essential?

• Wetting agent only
• Emulsifying agent
• Antioxidant only
• Chelating agent only

Correct Answer: Emulsifying agent

Q14. Which test is commonly used to assess the spreadability of a paste?

• Melting point determination
• Parallel plate method (spreadability apparatus)
• pH titration curve
• Karl Fischer titration

Correct Answer: Parallel plate method (spreadability apparatus)

Q15. Which property of a paste base most affects the ease of application and film formation on skin?

• Volatile impurity content
• Rheological characteristics and base composition
• Compression strength
• Melting point of the active drug

Correct Answer: Rheological characteristics and base composition

Q16. For incorporation of an insoluble powder into an oily base, the preferred sequence is:

• Mix base with powder without levigation
• Levigate the powder in a suitable levigating agent then incorporate into the base
• Dissolve the powder in water and add to the base
• Sublimate the powder directly into the base

Correct Answer: Levigate the powder in a suitable levigating agent then incorporate into the base

Q17. Which of the following is NOT typically a concern in paste formulation?

• Particle agglomeration
• Drug–excipient compatibility
• Radioactive contamination from excipients
• Microbial contamination in aqueous systems

Correct Answer: Radioactive contamination from excipients

Q18. Why is control of temperature important during preparation of many pastes?

• To ensure volatile solvents evaporate completely
• To avoid degradation of thermolabile drugs and maintain desirable viscosity
• To make the product sterile by heating
• Temperature has no effect on paste quality

Correct Answer: To avoid degradation of thermolabile drugs and maintain desirable viscosity

Q19. Which analytical study is most appropriate to assess chemical stability of an API in a paste?

• Organoleptic testing only
• Accelerated stability testing (ICH conditions) with assay by validated method
• Density measurement
• Simple pH paper test only

Correct Answer: Accelerated stability testing (ICH conditions) with assay by validated method

Q20. Which of the following bases is commonly used for oily pastes?

• Hydrophilic ointment
• Petrolatum (hydrocarbon base)
• Aqueous gel only
• Isotonic saline

Correct Answer: Petrolatum (hydrocarbon base)

Q21. In topical pastes intended to absorb exudate, which ingredient is particularly useful?

• Silica gel or starch
• Sucrose
• Glycerol
• Polyethylene glycol 400

Correct Answer: Silica gel or starch

Q22. Which parameter is critical for ensuring uniform distribution of drug in a paste?

• Spatulation technique and adequate mixing
• Using the largest possible particle size
• Keeping the paste at freezing temperatures
• Avoiding levigation

Correct Answer: Spatulation technique and adequate mixing

Q23. Franz diffusion cell testing is used in paste evaluation to determine:

• Microbial limits
• In vitro percutaneous drug release/absorption
• Viscosity at shear 0
• Melting point

Correct Answer: In vitro percutaneous drug release/absorption

Q24. Which of the following is an important consideration when selecting a levigating agent for an insoluble drug powder?

• The levigating agent must be a strong oxidizer
• Compatibility with both the powder and the final base
• It must be miscible with ethanol only
• It should be highly volatile

Correct Answer: Compatibility with both the powder and the final base

Q25. Are topical pastes generally required to be sterile?

• Yes, all pastes must be sterile
• No, most non-occlusive topical pastes are non-sterile but must meet microbial limits
• Only pastes for ophthalmic use need no sterility
• Pastes are always prepared using aseptic filtration

Correct Answer: No, most non-occlusive topical pastes are non-sterile but must meet microbial limits

Q26. Which test specifically evaluates the microbial quality of a paste?

• Viscosity test
• Microbial limit test (total viable counts and specified organisms)
• pH measurement
• Spreadability test

Correct Answer: Microbial limit test (total viable counts and specified organisms)

Q27. What is the primary function of a wetting agent in paste formulation?

• To raise melting point of the base
• To decrease surface tension and improve contact between powders and vehicle
• To act as the main preservative
• To color the paste

Correct Answer: To decrease surface tension and improve contact between powders and vehicle

Q28. Which of the following would most likely decrease the percutaneous absorption of an active in a paste?

• Decreasing particle size
• Using an occlusive hydrocarbon base with very low drug solubility
• Including penetration enhancers
• Using a lipophilic solvent that increases drug solubility

Correct Answer: Using an occlusive hydrocarbon base with very low drug solubility

Q29. During QC, which measurement gives information about the force needed to initiate flow of a paste?

• Yield value determination
• pH measurement
• Loss on drying only
• Particle count

Correct Answer: Yield value determination

Q30. What is an appropriate first step if a formulated paste shows phase separation during storage?

• Ignore it and continue distribution
• Investigate formulation: check excipient compatibility, emulsifier levels and processing conditions
• Increase storage temperature indefinitely
• Remove active ingredient

Correct Answer: Investigate formulation: check excipient compatibility, emulsifier levels and processing conditions

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