Monophasic liquids – Lotions MCQs With Answer

Introduction: Monophasic liquids for topical use, often termed solution lotions, are clear, single-phase preparations designed for uniform dosing and rapid drug release on skin. For B. Pharm students, mastering formulation principles—solubility, co-solvents (water, ethanol, propylene glycol), humectants (glycerin), buffers, preservatives (parabens, phenoxyethanol), chelators (EDTA), and surfactants (polysorbates)—is essential. Key attributes include skin-compatible pH (4.5–6.5), clarity, appropriate viscosity, antimicrobial protection, and patient acceptability. Quality control covers pH, viscosity (Brookfield), specific gravity, clarity, microbial limits, and antimicrobial effectiveness (USP <51>). Stability and packaging (HDPE, airless pumps) help prevent evaporation, oxidation, and contamination. These MCQs deepen understanding of formulation design, excipient selection, rheology, labeling, and GMP-based testing. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which statement best defines a monophasic lotion?

• A clear, single-phase solution intended for external application
• A dispersion of insoluble solids in a liquid vehicle
• An oil-in-water emulsion with dispersed droplets
• A water-in-oil emulsion for occlusive therapy

Correct Answer: A clear, single-phase solution intended for external application

Q2. Which solvent system is most suitable for a monophasic lotion containing both hydrophilic and moderately lipophilic actives?

• Purified water alone
• Ethanol–water co-solvent system
• Liquid paraffin
• Silicone oil

Correct Answer: Ethanol–water co-solvent system

Q3. What is the primary role of humectants in monophasic lotions?

• To reduce interfacial tension and form emulsions
• To increase water retention and improve skin hydration
• To act as primary preservatives against microbes
• To provide an occlusive barrier on the skin

Correct Answer: To increase water retention and improve skin hydration

Q4. Which excipient is commonly used as a humectant in monophasic lotions?

• Glycerin
• Zinc oxide
• Beeswax
• Liquid paraffin

Correct Answer: Glycerin

Q5. What is the ideal pH range for skin-friendly monophasic lotions?

• 2.0–3.0
• 4.5–6.5
• 7.5–9.0
• 9.5–11.0

Correct Answer: 4.5–6.5

Q6. Which nonionic surfactant is preferred as a solubilizer for fragrances in solution lotions?

• Polysorbate 20
• Sodium lauryl sulfate
• Cetyltrimethylammonium bromide
• Sorbitan stearate (Span 60)

Correct Answer: Polysorbate 20

Q7. Which rheological behavior best describes a simple monophasic lotion without polymeric thickener?

• Newtonian flow
• Bingham plastic behavior
• Pseudoplastic (shear-thinning) behavior
• Dilatant (shear-thickening) behavior

Correct Answer: Newtonian flow

Q8. Which polymer is suitable to slightly thicken a solution lotion while maintaining clarity?

• Hydroxyethyl cellulose (HEC)
• Microcrystalline cellulose
• Starch
• Talc

Correct Answer: Hydroxyethyl cellulose (HEC)

Q9. Which preservative system is commonly effective in lotions within pH 4–8?

• Methylparaben + Propylparaben
• Benzoic acid alone at pH 7
• Chlorhexidine at pH > 9 only
• Phenol at very low concentrations

Correct Answer: Methylparaben + Propylparaben

Q10. What is the primary function of disodium EDTA in monophasic lotions?

• Chelates metal ions to enhance preservative efficacy and stability
• Acts as the main antioxidant
• Serves as a plasticizer for packaging
• Provides fragrance

Correct Answer: Chelates metal ions to enhance preservative efficacy and stability

Q11. Which label statement is NOT appropriate for a monophasic lotion (solution) with no suspended matter?

• “Shake well before use”
• “For external use only”
• “Avoid contact with eyes”
• “Store below 25°C”

Correct Answer: “Shake well before use”

Q12. Which instrument is most suitable for routine viscosity measurement of low-to-medium viscosity lotions?

• Brookfield rotational viscometer with appropriate spindle
• Falling sphere viscometer
• UV–Vis spectrophotometer
• Flame photometer

Correct Answer: Brookfield rotational viscometer with appropriate spindle

Q13. How is clarity typically assessed in monophasic lotions during QC?

• Visual inspection against black and white backgrounds
• Scanning electron microscopy
• X-ray diffraction
• Dynamic light scattering

Correct Answer: Visual inspection against black and white backgrounds

Q14. For a weak base intended for a solution lotion, which strategy best balances solubility and skin permeation?

• Maintain high unionized fraction by raising pH well above pKa
• Lower pH to ionize for solubility and use co-solvent/penetration enhancer
• Use surfactant alone without pH or co-solvent adjustment
• Disperse as a fine suspension

Correct Answer: Lower pH to ionize for solubility and use co-solvent/penetration enhancer

Q15. Which antioxidant is most appropriate for an aqueous monophasic lotion prone to oxidative degradation?

• Sodium metabisulfite
• Butylated hydroxytoluene (BHT)
• Tocopherol acetate
• Rosemary oil

Correct Answer: Sodium metabisulfite

Q16. Which USP chapter evaluates preservative effectiveness in nonsterile topical products?

• <51>
• <61>
• <71>
• <621>

Correct Answer: <51>

Q17. Which packaging best minimizes evaporation and contamination for alcohol-containing lotions?

• Airless pump bottle
• Amber wide-mouth jar
• Open-top tray
• Paper sachet

Correct Answer: Airless pump bottle

Q18. Which co-solvent is commonly used with water to enhance drug solubility and skin penetration?

• Propylene glycol
• Mineral oil
• Isopropyl myristate
• Paraffin wax

Correct Answer: Propylene glycol

Q19. Which statement about parabens in monophasic lotions is TRUE?

• Their activity can be reduced by nonionic surfactants due to micellar partitioning
• They are most active at strongly alkaline pH
• They provide reliable antiviral activity at all pH values
• They cannot be used with any alcohol-containing systems

Correct Answer: Their activity can be reduced by nonionic surfactants due to micellar partitioning

Q20. Which buffer is skin-friendly and suitable for maintaining pH around 5.5 in lotions?

• Citrate buffer
• Borate buffer
• Carbonate buffer
• Ammonia buffer

Correct Answer: Citrate buffer

Q21. A clear solution lotion turns hazy when stored at 5°C. What is the most appropriate corrective action?

• Increase co-solvent proportion to prevent precipitation
• Add more electrolyte to “salt out” the solute
• Switch to a suspension
• Increase fragrance concentration

Correct Answer: Increase co-solvent proportion to prevent precipitation

Q22. If the target drug strength is 2% w/v in 250 mL of lotion, how many grams of drug are required?

• 2.5 g
• 5.0 g
• 10.0 g
• 20.0 g

Correct Answer: 5.0 g

Q23. Which excipient can function both as a humectant and a skin penetration enhancer in solution lotions?

• Propylene glycol
• Mineral oil
• Beeswax
• Talc

Correct Answer: Propylene glycol

Q24. According to microbial limits for topical nonsterile products, which pathogens must be absent?

• Escherichia coli and Salmonella
• Candida albicans and Aspergillus niger
• Staphylococcus aureus and Pseudomonas aeruginosa
• Bacillus subtilis and Micrococcus luteus

Correct Answer: Staphylococcus aureus and Pseudomonas aeruginosa

Q25. Which excipient can reduce the tacky feel of glycerin-rich lotions while maintaining clarity?

• 1,3-Propanediol
• Beeswax
• Mineral oil
• Lanolin

Correct Answer: 1,3-Propanediol

Q26. Which additional caution is appropriate for ethanol-containing monophasic lotions?

• “Flammable—keep away from fire or flame”
• “Sterile—do not touch tip”
• “Shake vigorously before use”
• “For oral use only”

Correct Answer: “Flammable—keep away from fire or flame”

Q27. Which instrument provides the most accurate pH measurement for lotions during QC?

• Calibrated pH meter
• pH indicator paper
• Conductivity meter
• Refractometer

Correct Answer: Calibrated pH meter

Q28. Which accelerated stability condition aligns with ICH guidelines for aqueous topical formulations?

• 25°C/60% RH for 12 months
• 30°C/65% RH for 3 months
• 40°C/75% RH for 6 months
• 50°C/95% RH for 1 month

Correct Answer: 40°C/75% RH for 6 months

Q29. What is the primary pharmaceutical rationale for adding fragrance to a solution lotion?

• To mask unpleasant odors and improve patient acceptability
• To increase antimicrobial activity
• To enhance viscosity
• To buffer the pH

Correct Answer: To mask unpleasant odors and improve patient acceptability

Q30. A hydrophilic drug degrades rapidly below pH 5. Which target pH best balances stability and skin compatibility in a monophasic lotion?

• pH 4.5
• pH 5.0
• pH 6.0
• pH 8.0

Correct Answer: pH 6.0

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