Monophasic liquids – Ear drops MCQs With Answer

Introduction

Monophasic liquids (ear drops) are homogeneous otic solutions designed for safe, effective delivery of drugs into the external auditory canal. For B. Pharm students, mastering otic formulation involves understanding solvent systems (water, glycerin, propylene glycol, oils), pH control, tonicity, viscosity enhancers, preservatives, antioxidants, and penetration enhancers. Key pharmaceutics principles include sterility considerations (especially with perforated tympanic membrane), microbial quality, preservative efficacy, stability, packaging, labeling (“For otic use only”), and patient counseling (warming drops, instillation technique). Therapeutic categories include cerumenolytics, antimicrobials, corticosteroids, and acidifying agents. This knowledge integrates formulation science, quality control, and clinical safety to optimize efficacy and comfort. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which best describes a monophasic ear drop in pharmaceutics?

• A biphasic suspension intended for the middle ear
• A homogeneous single-phase liquid dosage form intended for otic use
• An emulsion designed for ophthalmic application
• A transdermal solution for percutaneous absorption

Correct Answer: A homogeneous single-phase liquid dosage form intended for otic use

Q2. Which vehicle is commonly used in ear drops to increase viscosity and reduce canal edema due to its hygroscopic nature?

• Glycerin
• Isopropyl myristate
• Polyethylene glycol 4000
• Liquid paraffin (mineral oil) only

Correct Answer: Glycerin

Q3. Which preservative is cationic and may be inactivated by anionic surfactants in otic formulations?

• Benzalkonium chloride
• Methylparaben
• Thimerosal
• Sorbic acid

Correct Answer: Benzalkonium chloride

Q4. What pH range is generally preferred for otic solutions to discourage microbial growth while maintaining comfort?

• 1.0–2.0
• 4.0–5.5
• 6.8–7.4
• 8.0–9.0

Correct Answer: 4.0–5.5

Q5. Which statement about isotonicity in ear drops is most accurate?

• Strict isotonicity is mandatory to avoid severe pain
• Isotonicity is less critical than in ophthalmics but helps reduce irritation
• Hypertonic solutions are always preferred
• Hypotonic solutions are contraindicated

Correct Answer: Isotonicity is less critical than in ophthalmics but helps reduce irritation

Q6. When is sterility strongly recommended or required for otic solutions?

• Always, regardless of use
• Only for oily vehicles
• When the tympanic membrane is perforated or after ear surgery
• When preservatives are not used

Correct Answer: When the tympanic membrane is perforated or after ear surgery

Q7. Which excipient is commonly used to increase residence time of aqueous ear drops by enhancing viscosity?

• Hydroxypropyl methylcellulose (HPMC)
• Sodium lauryl sulfate
• Magnesium stearate
• Mannitol

Correct Answer: Hydroxypropyl methylcellulose (HPMC)

Q8. Which antioxidant is most appropriate for oil-based otic solutions?

• Sodium metabisulfite
• Butylated hydroxytoluene (BHT)
• Ascorbic acid
• Ethylenediaminetetraacetic acid (EDTA)

Correct Answer: Butylated hydroxytoluene (BHT)

Q9. Which key labeling statement is mandatory for ear drops?

• For ophthalmic use only
• For otic use only
• For oral use only
• Shake well before use (always)

Correct Answer: For otic use only

Q10. Which counseling step helps minimize dizziness or vertigo on instillation?

• Refrigerate and use cold
• Warm the bottle in hands to near body temperature
• Use immediately after vigorous shaking
• Lie on the opposite side of the affected ear

Correct Answer: Warm the bottle in hands to near body temperature

Q11. Proper instillation technique for adults involves pulling the auricle:

• Downward and backward
• Straight outward only
• Upward and backward
• Downward and forward

Correct Answer: Upward and backward

Q12. Which agent is a common cerumenolytic in ear drops?

• Carbamide peroxide
• Lidocaine hydrochloride
• Phenylephrine
• Zinc sulfate

Correct Answer: Carbamide peroxide

Q13. Which antimicrobial ear drop is considered safe in patients with a perforated tympanic membrane?

• Neomycin
• Gentamicin
• Ofloxacin
• Polymyxin B

Correct Answer: Ofloxacin

Q14. Which buffer is commonly used to maintain mildly acidic pH in otic solutions?

• Acetate buffer
• Carbonate buffer
• Phosphate buffer at pH 7.4
• Borate buffer at pH 9.2

Correct Answer: Acetate buffer

Q15. Which surfactant is often used at low levels to improve wetting and spreading in ear drops?

• Polysorbate 80
• Sodium dodecyl sulfate
• Cetyltrimethylammonium bromide
• Span 60 (sorbitan stearate, high HLB)

Correct Answer: Polysorbate 80

Q16. Which test evaluates the performance of preservatives in multi-dose otic solutions?

• Bacterial endotoxin test
• Antimicrobial effectiveness test (USP <51>)
• Particulate matter test
• Disintegration test

Correct Answer: Antimicrobial effectiveness test (USP <51>)

Q17. The preferred container for peroxide-containing ear drops to improve stability is:

• Clear LDPE dropper bottle
• Amber glass dropper bottle
• Metal canister
• Paper-laminated sachet

Correct Answer: Amber glass dropper bottle

Q18. Which preservative is more stable in acidic solutions and may volatilize at elevated temperatures?

• Chlorobutanol
• Phenol
• Sorbic acid
• Benzyl alcohol

Correct Answer: Chlorobutanol

Q19. In ear drops, propylene glycol primarily functions as a:

• Flavoring agent
• Penetration-enhancing cosolvent that can also increase viscosity
• Suspending agent
• Tonicity adjuster only

Correct Answer: Penetration-enhancing cosolvent that can also increase viscosity

Q20. Which statement best reflects the role of viscosity in otic solutions?

• Very high viscosity always improves efficacy
• Moderate viscosity increases residence time without occluding the canal
• Low viscosity is always preferred
• Viscosity has no impact on drug residence time

Correct Answer: Moderate viscosity increases residence time without occluding the canal

Q21. The approximate volume delivered by a standard dropper per drop of liquid is about:

• 0.5 mL
• 0.05 mL
• 5 mL
• 0.005 mL

Correct Answer: 0.05 mL

Q22. Which is NOT typically a routine quality control test for nonsterile otic solutions?

• pH determination
• Viscosity measurement
• Sterility test for every batch
• Assay of active ingredient

Correct Answer: Sterility test for every batch

Q23. After instilling ear drops, patients should keep the treated ear facing upward for approximately:

• 10–15 seconds
• 30 seconds
• 3–5 minutes
• 20 minutes

Correct Answer: 3–5 minutes

Q24. Which formulation strategy primarily reduces stinging and discomfort upon otic instillation?

• Increasing alcohol content
• Adjusting pH to around 5 and limiting alcohol content
• Using hypertonic saline
• Adding anionic surfactants

Correct Answer: Adjusting pH to around 5 and limiting alcohol content

Q25. Which incompatibility is most relevant when using benzalkonium chloride in ear drops?

• Incompatibility with nonionic surfactants
• Inactivation by anionic surfactants
• Oxidation by EDTA
• Complexation with glycerin

Correct Answer: Inactivation by anionic surfactants

Q26. Why can ophthalmic solutions sometimes be used otically, whereas otic solutions should not be used in the eye?

• Otic solutions are always hypertonic
• Ophthalmic solutions meet stricter sterility and irritancy standards
• Ophthalmic solutions contain no preservatives
• Ear canal absorbs drugs faster than the eye

Correct Answer: Ophthalmic solutions meet stricter sterility and irritancy standards

Q27. According to USP <795>, the typical beyond-use date for a preserved, water-containing compounded otic solution stored at room temperature is up to:

• 7 days
• 14 days
• 30 days
• 90 days

Correct Answer: 30 days

Q28. Which agent is commonly used to adjust tonicity in otic solutions?

• Sodium chloride
• Calcium carbonate
• Starch
• Magnesium sulfate

Correct Answer: Sodium chloride

Q29. An acidifying ear drop commonly used for otitis externa prevention contains acetic acid at approximately:

• 0.1%
• 1%
• 2%
• 10%

Correct Answer: 2%

Q30. Which agent in ear drops poses a significant ototoxicity risk if the tympanic membrane is perforated?

• Neomycin
• Hydrocortisone
• Acetic acid
• Carbamide peroxide

Correct Answer: Neomycin

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