Antimicrobials: Boric acid MCQs With Answer is a focused study aid tailored for B.Pharm students preparing for exams and practicals. This concise, keyword-rich introduction covers boric acid chemistry, pharmacology, antimicrobial spectrum, formulations, dosing (including vaginal suppositories), mechanism of action, toxicity, stability, and quality control tests. Emphasis is on pharmaceutics and clinical pharmacy relevance—ophthalmic solutions, topical antiseptics, and antifungal uses—so students learn practical applications and analytical methods like titration and curcumin test. Clear, exam-style MCQs reinforce critical concepts such as pKa, solubility, compatibility, and safety considerations for effective pharmaceutical practice. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the chemical formula of boric acid?
- H3BO3
- H2BO2
- H4BO4
- B2O3
Correct Answer: H3BO3
Q2. Which property best describes boric acid’s primary antimicrobial action?
- Strong bactericidal at microgram concentrations
- Weak antiseptic with antifungal activity
- Broad-spectrum antiviral agent
- Powerful systemic antibiotic
Correct Answer: Weak antiseptic with antifungal activity
Q3. What is the molecular weight (approx.) of boric acid (H3BO3)?
- 61.83 g/mol
- 55.85 g/mol
- 69.62 g/mol
- 47.01 g/mol
Correct Answer: 61.83 g/mol
Q4. Which statement about boric acid’s acid-base behavior is correct?
- It is a strong Brønsted acid (pKa < 1)
- It acts mainly as a Lewis acid accepting hydroxide
- It is a strong base
- It does not ionize in water
Correct Answer: It acts mainly as a Lewis acid accepting hydroxide
Q5. What is the approximate pKa value of boric acid?
- 3.8
- 7.0
- 9.24
- 12.5
Correct Answer: 9.24
Q6. Which of the following is a common ophthalmic concentration of boric acid used for eye washes?
- 0.5% w/v
- 1.0% w/v
- 2.7% w/v
- 10% w/v
Correct Answer: 2.7% w/v
Q7. Which microbial group is boric acid particularly effective against in topical applications?
- Gram-negative bacilli only
- Fungi such as Candida species
- Acid-fast mycobacteria
- All viruses
Correct Answer: Fungi such as Candida species
Q8. What is the typical dose of boric acid used as a vaginal suppository for recurrent candidiasis?
- 50 mg nightly
- 200 mg twice daily
- 600 mg once nightly
- 1500 mg once weekly
Correct Answer: 600 mg once nightly
Q9. Which method is commonly used for assay of boric acid in pharmaceutical quality control?
- Titration with NaOH after complexation with mannitol
- Direct titration with HCl
- Colorimetric test with potassium permanganate
- Gravimetric precipitation with silver nitrate
Correct Answer: Titration with NaOH after complexation with mannitol
Q10. Which analytical reagent yields a characteristic pink/red complex for boron detection?
- Ninhydrin
- Curcumin (rosocyanine test)
- Biuret reagent
- Dragendorff’s reagent
Correct Answer: Curcumin (rosocyanine test)
Q11. How does boric acid primarily exert antifungal effects?
- Inhibition of cell wall synthesis via beta-lactam binding
- Formation of borate complexes that disrupt enzyme function
- Direct DNA intercalation
- Inhibition of viral reverse transcriptase
Correct Answer: Formation of borate complexes that disrupt enzyme function
Q12. Which statement about boric acid solubility is true?
- It is insoluble in water
- Solubility decreases with temperature
- It is soluble in water and solubility increases with temperature
- It is highly soluble in nonpolar solvents like hexane
Correct Answer: It is soluble in water and solubility increases with temperature
Q13. Which functional interaction makes boric acid useful as a buffering agent in formulations?
- Formation of sulfate salts
- Interaction with cis-diols to form borate esters and establishing borate buffer systems
- Complexation with heavy metals
- Strong oxidation of organic acids
Correct Answer: Interaction with cis-diols to form borate esters and establishing borate buffer systems
Q14. Boric acid is contraindicated or used with caution in which population due to reproductive toxicity?
- Elderly patients with hypertension
- Pregnant women
- Patients with controlled diabetes
- Children over 12 years only
Correct Answer: Pregnant women
Q15. Which route of exposure leads to significant systemic absorption of boric acid?
- Intact skin application only
- Mucosal or gastrointestinal exposure (ingestion or vaginal mucosa)
- External hair application
- Inhalation of dry powder is completely non-absorbable
Correct Answer: Mucosal or gastrointestinal exposure (ingestion or vaginal mucosa)
Q16. Which physicochemical property describes boric acid’s structure?
- Tetrahedral boron center
- Trigonal planar boron with three hydroxyl groups
- Linear diatomic molecule
- Polymeric metallic lattice
Correct Answer: Trigonal planar boron with three hydroxyl groups
Q17. How is pharmaceutical-grade boric acid commonly prepared from borax?
- Oxidation of borax with hydrogen peroxide
- Acidification of borax solution to precipitate boric acid
- Electrolytic reduction of borax
- Sublimation of borax at room temperature
Correct Answer: Acidification of borax solution to precipitate boric acid
Q18. Which of the following is a typical pharmaceutical formulation of boric acid?
- Injectable sterile boric acid solution for IV use
- Vaginal suppositories, ophthalmic washes, topical powders
- High-dose oral tablets for systemic infections
- Inhalation aerosol for pulmonary delivery
Correct Answer: Vaginal suppositories, ophthalmic washes, topical powders
Q19. Which safety concern is most associated with acute oral ingestion of boric acid?
- Immediate allergic anaphylaxis in all patients
- Gastrointestinal irritation, vomiting, and potential neurotoxicity at high doses
- Severe hypoglycemia
- High risk of acute myocardial infarction
Correct Answer: Gastrointestinal irritation, vomiting, and potential neurotoxicity at high doses
Q20. Which organ is primarily responsible for elimination of absorbed boron in humans?
- Liver via bile
- Kidneys via urine
- Exhaled via lungs
- Stored permanently in adipose tissue
Correct Answer: Kidneys via urine
Q21. Which quality control parameter is important for sterile ophthalmic boric acid solutions?
- Assay by gas chromatography
- Sterility test and particulate matter evaluation
- Blood level monitoring
- Oxidative stability in presence of peroxide only
Correct Answer: Sterility test and particulate matter evaluation
Q22. In manufacturing, which excipient is frequently combined with boric acid to form a borate buffer?
- Sodium chloride
- Sodium borate (borax)
- Magnesium stearate
- Calcium carbonate
Correct Answer: Sodium borate (borax)
Q23. Which is a known environmental concern regarding boric acid and borates?
- Highly volatile leading to air pollution
- Toxicity to aquatic organisms at elevated concentrations
- Rapid biodegradation producing greenhouse gases
- Complete inertness with no ecological impact
Correct Answer: Toxicity to aquatic organisms at elevated concentrations
Q24. Which laboratory test is appropriate to determine the minimum inhibitory concentration (MIC) of boric acid against Candida?
- Disk diffusion without dilution
- Broth microdilution method
- Gram staining intensity
- Thermal melting curve
Correct Answer: Broth microdilution method
Q25. Which chemical reaction can boric acid undergo with alcohols in formulation chemistry?
- Oxidation to boron oxide
- Formation of borate esters
- Reduction to borane gas
- Halogenation at boron center
Correct Answer: Formation of borate esters
Q26. Which statement about boric acid’s antimicrobial resistance profile is most accurate?
- Rapid, widespread bacterial resistance emerges within days
- Low likelihood of classical resistance due to nonspecific modes of action
- It functions as a beta-lactamase inhibitor
- It promotes plasmid-mediated resistance transfer
Correct Answer: Low likelihood of classical resistance due to nonspecific modes of action
Q27. Which of the following is a sign of chronic boric acid toxicity?
- Testicular atrophy and reproductive toxicity (observed in animals)
- Immediate skin whitening
- Permanent hearing loss
- Elevated blood glucose only
Correct Answer: Testicular atrophy and reproductive toxicity (observed in animals)
Q28. Which pH adjustment effect does boric acid typically impart in aqueous formulations?
- Strongly raises pH to >12
- Provides weak acidic buffering, often near neutral when combined with borate
- Has no effect on pH
- Instantly neutralizes all bases
Correct Answer: Provides weak acidic buffering, often near neutral when combined with borate
Q29. Which excipient incompatibility should be considered when formulating with boric acid?
- Strong polyols can complex with borate altering activity
- Neutral oils promote boric acid oxidation
- All proteins are entirely stable with boric acid
- It reacts vigorously with sodium chloride
Correct Answer: Strong polyols can complex with borate altering activity
Q30. Which physical property describes boric acid’s behaviour upon heating to high temperatures?
- Boils intact at 80°C
- Dehydrates to boron oxide around 170°C
- Explodes at 120°C
- Vaporizes without decomposition at 100°C
Correct Answer: Dehydrates to boron oxide around 170°C
Q31. Which formulation type commonly uses boric acid for its mild antiseptic and buffering properties?
- Oral insulin tablets
- Ophthalmic washes and eye drops
- Intravenous antibiotics
- Inhalable corticosteroid aerosols
Correct Answer: Ophthalmic washes and eye drops
Q32. Which statement about dermal absorption of boric acid is correct?
- Poorly absorbed through intact skin but better absorbed through damaged skin or mucosa
- Completely absorbed through intact skin within seconds
- Never absorbed through mucous membranes
- Absorption is identical to intravenous injection
Correct Answer: Poorly absorbed through intact skin but better absorbed through damaged skin or mucosa
Q33. Which clinical use of boric acid is supported for azole-resistant vaginal candidiasis?
- Topical ointment applied to the arm
- Oral tablets once daily
- Vaginal suppositories of 600 mg nightly
- Weekly intramuscular injections
Correct Answer: Vaginal suppositories of 600 mg nightly
Q34. Which laboratory precaution is important when preparing boric acid sterile solutions?
- Autoclave parameters are unnecessary
- Use of pyrogen-free water and aseptic technique or terminal sterilization as appropriate
- Sterility is not required for ophthalmic use
- Only filtration through 5 µm filters is acceptable
Correct Answer: Use of pyrogen-free water and aseptic technique or terminal sterilization as appropriate
Q35. Which test would detect particulate contamination in an ophthalmic boric acid solution?
- Particulate matter test (light obscuration method)
- pH test only
- Assay by titration only
- Melting point determination
Correct Answer: Particulate matter test (light obscuration method)
Q36. Which of the following best describes boric acid’s role in contact lens care solutions historically?
- Primary disinfectant replacing all others
- Buffering and mild antimicrobial adjunct
- Emulsifier to stabilize lipids
- Sole surfactant for cleaning protein deposits
Correct Answer: Buffering and mild antimicrobial adjunct
Q37. Which reagent can increase boric acid titratable acidity by forming a stronger acid complex?
- Mannitol
- Sodium chloride
- Sulfuric acid
- Potassium nitrate
Correct Answer: Mannitol
Q38. Which of the following is a contraindication for internal/oral use of boric acid?
- Use as an insecticide in household traps
- Pediatric ingestion and in pregnant women due to systemic toxicity
- Use as a topical foot powder
- Use in ophthalmic rinse only
Correct Answer: Pediatric ingestion and in pregnant women due to systemic toxicity
Q39. Which statement about boric acid’s compatibility with metals is most appropriate?
- Forms explosive alloys with aluminum
- Generally compatible; primary concern is complexation with polyols rather than metals
- Reacts violently with stainless steel
- Always catalyzes metal corrosion rapidly
Correct Answer: Generally compatible; primary concern is complexation with polyols rather than metals
Q40. Which environmental pH change will favor formation of tetrahydroxyborate ion from boric acid?
- Strongly acidic pH (pH < 2)
- Alkaline pH (higher pH promoting hydroxide addition)
- Neutral pH has no effect
- Only high ionic strength, not pH, affects formation
Correct Answer: Alkaline pH (higher pH promoting hydroxide addition)
Q41. Which safety labeling is appropriate for pharmaceutical containers of boric acid?
- No warnings required
- Include toxicity, avoid ingestion, keep out of reach of children
- Label as explosive
- Label as radioisotope
Correct Answer: Include toxicity, avoid ingestion, keep out of reach of children
Q42. Which of the following is an observed adverse effect from topical boric acid use at high concentrations?
- Photosynthetic enhancement of skin
- Skin irritation and dermatitis
- Instant permanent tattooing
- Universal increased hair growth
Correct Answer: Skin irritation and dermatitis
Q43. Which pharmacokinetic concept is true for boric acid?
- Extensively metabolized to active metabolites
- Poorly metabolized and excreted largely unchanged in urine
- Stored mainly in adipose tissue for years
- Rapidly converted to glucose
Correct Answer: Poorly metabolized and excreted largely unchanged in urine
Q44. Which preservative role can boric acid serve in topical ophthalmic products?
- Main preservative for multi-dose steroid injections
- Mild preservative and pH adjuster in some eye drops
- Primary heavy-metal chelator in IV solutions
- Preservative for powdered vaccines
Correct Answer: Mild preservative and pH adjuster in some eye drops
Q45. Which reaction indicates boric acid presence in a qualitative lab test?
- Formation of a blue precipitate with zinc chloride
- Pink/red color with curcumin under acidic conditions
- Fizzing with sodium bicarbonate
- Black precipitate with lead acetate
Correct Answer: Pink/red color with curcumin under acidic conditions
Q46. Which manufacturing precaution helps maintain boric acid stability in formulations?
- Exposure to strong bases during storage
- Protection from extreme heat and moisture
- Continuous UV irradiation
- Storage in open containers
Correct Answer: Protection from extreme heat and moisture
Q47. Which statement about boric acid’s role in antifungal therapy is correct?
- It is first-line systemic antifungal for invasive candidiasis
- It can be used as a topical or intravaginal agent for resistant superficial candidiasis
- It is ineffective against yeast species
- Use is limited to parenteral administration only
Correct Answer: It can be used as a topical or intravaginal agent for resistant superficial candidiasis
Q48. Which concentration consideration is critical for boric acid ophthalmic preparations to minimize irritation?
- Using extremely hypertonic concentrations (>10%) is preferred
- Maintaining near-isotonicity (e.g., around 2.7% w/v) to reduce discomfort
- Always making highly acidic solutions (pH < 2)
- Omitting all buffering systems
Correct Answer: Maintaining near-isotonicity (e.g., around 2.7% w/v) to reduce discomfort
Q49. Which test is most relevant to evaluate the antimicrobial efficacy of a boric acid-containing topical formulation?
- Antimicrobial preservative efficacy test (challenge test)
- Melting point determination
- Loss on drying only
- Color match test
Correct Answer: Antimicrobial preservative efficacy test (challenge test)
Q50. Which precaution should pharmacists counsel patients about when recommending boric acid suppositories?
- It is safe for use during pregnancy without restriction
- Avoid use during pregnancy and keep out of reach of children; follow prescribed dose and duration
- They can be crushed for oral use
- They must be injected if no improvement occurs
Correct Answer: Avoid use during pregnancy and keep out of reach of children; follow prescribed dose and duration
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