Monophasic liquids – Throat paints MCQs With Answer

Monophasic liquids – Throat paints are viscous, single-phase solutions designed for local application to the oropharyngeal mucosa. For B. Pharm students, this topic links core pharmaceutics with practical extemporaneous compounding. Key formulation elements include glycerin/propylene glycol/ethanol vehicles, viscosity and mucoadhesion for prolonged residence, suitable actives (antiseptics like povidone-iodine/phenol; local anesthetics like lidocaine/benzocaine), pH optimization, preservative efficacy (or self-preservation via high glycerin), stability (light/volatilization sensitivity of iodine), and quality control (viscosity, assay, pH, microbial limits). Safe use hinges on labeling (external use, do not swallow), packaging (amber glass with applicator), and patient-specific considerations (contraindications, pediatric cautions). Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What best describes a monophasic liquid dosage form?

• Single-phase system with solutes molecularly dispersed in a solvent
• Two-phase system with solid suspended in liquid
• Emulsion of oil in water with surfactant
• Aerosolized foam for inhalation

Correct Answer: Single-phase system with solutes molecularly dispersed in a solvent

Q2. What is a throat paint in pharmaceutics?

• Viscous monophasic solution applied to oropharyngeal mucosa using a swab
• Sterile injectable solution for systemic use
• Sugar-based lozenge for sucking
• Pressurized spray for nasal mucosa

Correct Answer: Viscous monophasic solution applied to oropharyngeal mucosa using a swab

Q3. The primary purpose of high viscosity in a throat paint is to:

• Prolong contact time and enhance local drug residence
• Improve sweetness
• Prevent oxidation
• Increase systemic absorption

Correct Answer: Prolong contact time and enhance local drug residence

Q4. The most common base vehicle used in throat paints is:

• Glycerin
• Liquid paraffin
• Mineral oil
• Silicone oil

Correct Answer: Glycerin

Q5. The preferred method of applying a throat paint is:

• Cotton swab/brush
• Oral syringe
• Nebulizer
• Nasogastric tube

Correct Answer: Cotton swab/brush

Q6. Which excipient is commonly used as a mucoadhesive polymer in throat paints?

• Sodium carboxymethyl cellulose
• Talc
• Magnesium stearate
• Starch glycolate

Correct Answer: Sodium carboxymethyl cellulose

Q7. Which of the following is a suitable antiseptic active for a throat paint?

• Povidone-iodine
• Insulin
• Amoxicillin trihydrate
• Omeprazole

Correct Answer: Povidone-iodine

Q8. Why are throat paints classified as monophasic liquids?

• All components are molecularly dispersed with no undissolved solids
• They contain dispersed oil droplets
• They contain suspended solid particles
• They have two immiscible phases

Correct Answer: All components are molecularly dispersed with no undissolved solids

Q9. The best solvent system to dissolve benzocaine for a throat paint is:

• Ethanol–propylene glycol blend
• Purified water alone
• Liquid paraffin
• Castor oil

Correct Answer: Ethanol–propylene glycol blend

Q10. A typical concentration statement for povidone-iodine throat paint is:

• 10% w/v povidone-iodine (≈1% available iodine)
• 0.01% w/v povidone-iodine
• 50% w/v povidone-iodine
• Saturated iodine tincture only

Correct Answer: 10% w/v povidone-iodine (≈1% available iodine)

Q11. A critical stability concern for iodine-containing throat paints is:

• Light and volatilization of iodine
• Freezing
• Carbonation loss
• Photostability improvement with alkali

Correct Answer: Light and volatilization of iodine

Q12. Additional preservative may be unnecessary in a throat paint when:

• When glycerin content exceeds about 60% v/v
• When using purified water only
• When stored at 40°C
• When pH is exactly 7.4

Correct Answer: When glycerin content exceeds about 60% v/v

Q13. Preferred pH range for a lidocaine HCl throat paint is:

• Approximately 5.0–7.0
• Below 2.0
• Above 10.0
• Exactly 9.5

Correct Answer: Approximately 5.0–7.0

Q14. Which quality control test best correlates with mucosal retention time?

• Viscosity measurement at 25°C
• Refractive index
• Melting point
• Boiling point

Correct Answer: Viscosity measurement at 25°C

Q15. Recommended packaging for throat paints is:

• Amber glass bottle with tight closure and applicator
• Clear PET bottle without closure
• Aerosol can with propellant
• Metal tube with crimped end

Correct Answer: Amber glass bottle with tight closure and applicator

Q16. An essential auxiliary label for throat paints is:

• For external use only; do not swallow
• Shake well before use
• For intravenous use
• Store in freezer

Correct Answer: For external use only; do not swallow

Q17. The usual frequency of applying throat paints is:

• 2–4 times daily as directed
• Every 30 minutes
• Once weekly
• Every hour for 24 hours

Correct Answer: 2–4 times daily as directed

Q18. A key contraindication for iodine-containing throat paints is:

• Known hyperthyroidism or iodine sensitivity
• Hypertension
• Lactose intolerance
• Myopia

Correct Answer: Known hyperthyroidism or iodine sensitivity

Q19. A notable adverse effect associated with benzocaine throat paints is:

• Methemoglobinemia in susceptible patients
• Hyperglycemia
• Photosensitivity only
• Nephrolithiasis

Correct Answer: Methemoglobinemia in susceptible patients

Q20. Why should strong sweeteners/flavors be limited in throat paints?

• They encourage swallowing and reduce local contact time
• They increase solubility of all drugs
• They eliminate microbial growth
• They stabilize iodine by complexation

Correct Answer: They encourage swallowing and reduce local contact time

Q21. The correct order of compounding steps for a throat paint is:

• Dissolve actives in suitable solvent, add glycerin/viscosity agents, adjust volume, mix until homogeneous
• Add all powders to bottle and shake with water
• Melt drug, add to paraffin, homogenize
• Triturate with lactose and fill capsules

Correct Answer: Dissolve actives in suitable solvent, add glycerin/viscosity agents, adjust volume, mix until homogeneous

Q22. Why are throat paints often prepared extemporaneously?

• Short shelf life and need for patient-specific actives/strengths
• Lack of licensed pharmacists
• To avoid labeling
• Greater systemic bioavailability

Correct Answer: Short shelf life and need for patient-specific actives/strengths

Q23. The role of a humectant like glycerin in throat paints is to:

• Retain moisture and improve spreadability on mucosa
• Induce effervescence
• Provide sustained systemic release
• Act as propellant

Correct Answer: Retain moisture and improve spreadability on mucosa

Q24. Which local anesthetic form is most appropriate for aqueous throat paints?

• Lidocaine hydrochloride
• Procaine base
• Benzocaine base alone in water
• Bupivacaine base only

Correct Answer: Lidocaine hydrochloride

Q25. A practical strategy to enhance mucoadhesion in a throat paint is to:

• Include 1–2% w/v sodium CMC or carbomer
• Add talc 5%
• Use liquid paraffin base
• Reduce viscosity to near water

Correct Answer: Include 1–2% w/v sodium CMC or carbomer

Q26. The appropriate pharmacopoeial test for microbial quality of throat paints is:

• Microbial limits test as per USP/Ph. Eur. requirements
• Sterility test for parenterals
• Pyrogen test in rabbits
• Endotoxin test

Correct Answer: Microbial limits test as per USP/Ph. Eur. requirements

Q27. What is the pediatric caution for benzocaine-containing throat paints?

• Avoid use in children under 2 years due to methemoglobinemia risk
• Administer freely to neonates
• Safe with no restrictions
• Contraindicated only in elderly

Correct Answer: Avoid use in children under 2 years due to methemoglobinemia risk

Q28. Recommended storage for throat paints is:

• Store below 25°C, protect from light and moisture
• Keep in sunlight to prevent crystallization
• Store in open container
• Freeze before each use

Correct Answer: Store below 25°C, protect from light and moisture

Q29. How does viscosity influence local pharmacokinetics of throat paints?

• Increases residence time, improving local bioavailability without increasing systemic absorption
• Decreases drug stability
• Eliminates first-pass metabolism
• Guarantees zero-order release systemically

Correct Answer: Increases residence time, improving local bioavailability without increasing systemic absorption

Q30. A key difference between a throat paint and a gargle is that:

• Paint is a viscous, locally applied solution for prolonged mucosal contact; gargle is an aqueous rinse expelled after short contact
• Paint is swallowed; gargle is injected
• Paint is always sterile; gargle is not
• Paint contains suspending agent; gargle never contains solvents

Correct Answer: Paint is a viscous, locally applied solution for prolonged mucosal contact; gargle is an aqueous rinse expelled after short contact

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