Benoxinate MCQs With Answer

Benoxinate MCQs With Answer

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Introduction: Benoxinate MCQs With Answer provides B. Pharm students a focused review of benoxinate (also called oxybuprocaine), an ester-type topical ocular anesthetic. This concise, informative guide covers mechanism of action, pharmacokinetics, clinical uses (tonometry, foreign body removal, minor ocular procedures), dosing, adverse effects like corneal toxicity and hypersensitivity, metabolism by plasma esterases, and important precautions. Emphasis is placed on differential features from amide anesthetics, systemic toxicity risks, and formulation considerations to strengthen clinical and pharmacological understanding. Clear explanations and clinically relevant questions prepare students for exams and practical decision-making. ‘Now let’s test your knowledge with 30 MCQs on this topic.’

Q1. What is the primary pharmacological mechanism of benoxinate?

  • Inhibition of acetylcholinesterase
  • Blockade of voltage-gated sodium channels
  • Activation of GABA receptors
  • Agonism at opioid receptors

Correct Answer: Blockade of voltage-gated sodium channels

Q2. Benoxinate belongs to which chemical class of local anesthetics?

  • Amide-type local anesthetic
  • Ester-type local anesthetic
  • Ketone-based anesthetic
  • Ether-based anesthetic

Correct Answer: Ester-type local anesthetic

Q3. The usual ophthalmic concentration commonly used for benoxinate (oxybuprocaine) is:

  • 0.01%
  • 0.1%
  • 0.4%
  • 2.0%

Correct Answer: 0.4%

Q4. Which statement best describes the onset and typical duration of topical benoxinate ocular anesthesia?

  • Onset in 30–60 minutes; duration 12–24 hours
  • Onset in 20–30 seconds; duration 5–20 minutes
  • Onset in 5–10 minutes; duration 2–4 hours
  • Onset immediately; duration less than 5 seconds

Correct Answer: Onset in 20–30 seconds; duration 5–20 minutes

Q5. The primary metabolic pathway for benoxinate is:

  • Hepatic CYP450 oxidation
  • Glucuronidation in the liver
  • Hydrolysis by plasma and tissue esterases
  • Renal excretion unchanged

Correct Answer: Hydrolysis by plasma and tissue esterases

Q6. Which adverse effect is most associated with repeated topical ocular use of benoxinate?

  • Severe systemic hypertension
  • Corneal epithelial toxicity and delayed healing
  • Permanent glaucoma
  • Permanent pupil dilation

Correct Answer: Corneal epithelial toxicity and delayed healing

Q7. Which of the following is a common clinical use of benoxinate?

  • Long-term management of glaucoma
  • Topical anesthesia for tonometry and corneal procedures
  • Systemic analgesia for postoperative pain
  • Antibiotic prophylaxis after cataract surgery

Correct Answer: Topical anesthesia for tonometry and corneal procedures

Q8. A patient with a known PABA allergy may be at increased risk of hypersensitivity with benoxinate because:

  • Benoxinate is metabolized to PABA-related compounds
  • Benoxinate directly releases PABA upon contact
  • Benoxinate is an amide linked to PABA
  • Benoxinate contains a sulfate group cross-reactive with PABA

Correct Answer: Benoxinate is metabolized to PABA-related compounds

Q9. Which systemic toxicity signs are possible if significant systemic absorption of benoxinate occurs?

  • CNS excitation followed by depression and cardiovascular collapse
  • Hyperglycemia and polyuria
  • Renal tubular necrosis
  • Persistent tachyphylaxis without CNS effects

Correct Answer: CNS excitation followed by depression and cardiovascular collapse

Q10. Which precaution is most appropriate when using benoxinate in children?

  • Use high multiple doses for prolonged anesthesia
  • Avoid routine use and limit to necessary procedures with careful dosing
  • Always combine with systemic opioids
  • Use at double adult concentration due to faster metabolism

Correct Answer: Avoid routine use and limit to necessary procedures with careful dosing

Q11. Which of the following best explains why benoxinate has a short duration of action?

  • Poor receptor affinity
  • Rapid hydrolysis by esterases and limited tissue penetration
  • Strong binding to melanin in the eye
  • Intense protein binding prolongs immunity

Correct Answer: Rapid hydrolysis by esterases and limited tissue penetration

Q12. When preparing a benoxinate ophthalmic drop for tonometry, the pharmacist should counsel patients to expect:

  • A delayed numbness after 30 minutes
  • A brief stinging sensation followed by rapid numbness
  • Severe systemic dizziness immediately
  • Permanent loss of vision within hours

Correct Answer: A brief stinging sensation followed by rapid numbness

Q13. Compared with amide local anesthetics, ester anesthetics like benoxinate generally have:

  • Longer systemic half-lives and hepatic metabolism
  • Shorter duration and metabolism by esterases
  • No risk of allergic reactions
  • Better oral bioavailability

Correct Answer: Shorter duration and metabolism by esterases

Q14. Which of the following formulations is least appropriate for benoxinate use?

  • Topical ophthalmic solution for corneal anesthesia
  • Intravenous injection for systemic analgesia
  • Single-drop application before minor ocular procedures
  • Topical instillation for foreign body removal

Correct Answer: Intravenous injection for systemic analgesia

Q15. Cross-sensitivity between benoxinate and which class of compounds is a clinical concern?

  • Sulfonamides
  • Para-aminobenzoic acid (PABA) derivatives and other ester anesthetics
  • Beta-lactam antibiotics
  • Benzodiazepines

Correct Answer: Para-aminobenzoic acid (PABA) derivatives and other ester anesthetics

Q16. In case of accidental excessive ocular dosing of benoxinate, the immediate pharmacist advice should include:

  • Induce emesis
  • Rinse the eye with sterile saline and seek medical assessment
  • Advise oral activated charcoal
  • Apply topical steroids immediately

Correct Answer: Rinse the eye with sterile saline and seek medical assessment

Q17. Which pharmacokinetic property explains why benoxinate has minimal systemic effects after ocular application?

  • High oral bioavailability
  • Extensive first-pass hepatic metabolism
  • Rapid local hydrolysis by esterases and limited systemic absorption
  • Strong binding to plasma albumin preventing tissue entry

Correct Answer: Rapid local hydrolysis by esterases and limited systemic absorption

Q18. Which monitoring advice is most appropriate after instillation of benoxinate before in-office procedures?

  • Monitor blood glucose closely
  • Assess corneal integrity and ensure patient comfort; avoid rubbing the eye
  • Measure serum electrolytes immediately
  • Record daily blood pressure every hour

Correct Answer: Assess corneal integrity and ensure patient comfort; avoid rubbing the eye

Q19. A pharmacology student asks why benoxinate is not used for nerve blocks. The best answer is:

  • It is too potent systemically
  • Its short duration and topical formulation limit deeper nerve block utility
  • It causes irreversible nerve damage on injection
  • It only acts on muscarinic receptors

Correct Answer: Its short duration and topical formulation limit deeper nerve block utility

Q20. Which laboratory alteration is most likely after massive systemic absorption of ester anesthetics (general class effect, not common with topical doses)?

  • Hypokalemia due to renal losses
  • Metabolic alkalosis from enhanced bicarbonate
  • Signs of CNS toxicity on EEG and possible acidosis from hypoventilation
  • Marked leukocytosis

Correct Answer: Signs of CNS toxicity on EEG and possible acidosis from hypoventilation

Q21. Which patient history detail is most relevant before instilling benoxinate?

  • History of diabetes mellitus
  • History of severe allergic reactions to ester local anesthetics or PABA
  • History of seasonal allergic rhinitis
  • Past refractive surgery ten years ago only

Correct Answer: History of severe allergic reactions to ester local anesthetics or PABA

Q22. Which strategy reduces the risk of corneal toxicity with topical benoxinate?

  • Frequent repeated dosing over several days for better comfort
  • Limit use to brief procedures and avoid repeated prolonged applications
  • Combine with topical antibiotics routinely
  • Use at higher concentration to reduce frequency

Correct Answer: Limit use to brief procedures and avoid repeated prolonged applications

Q23. In the context of pharmacology, why is benoxinate often preferred for diagnostic ocular procedures?

  • It produces systemic sedation beneficial for patients
  • Rapid onset, adequate surface anesthesia, and short duration allowing quick recovery
  • It permanently desensitizes the cornea
  • It enhances intraocular pressure during tonometry

Correct Answer: Rapid onset, adequate surface anesthesia, and short duration allowing quick recovery

Q24. Which interaction is most relevant when considering benoxinate use?

  • Enhanced anticoagulant effect with warfarin via CYP450 inhibition
  • Risk of additive systemic toxicity with other local anesthetics if absorbed systemically
  • Antagonism of beta-blockers
  • Inactivation by ocular antibiotics on contact

Correct Answer: Risk of additive systemic toxicity with other local anesthetics if absorbed systemically

Q25. Which statement about benoxinate’s effect on diagnostic measurements is correct?

  • It permanently lowers intraocular pressure
  • It may transiently affect tear film and corneal reflexes, potentially altering some diagnostic tests
  • It increases corneal thickness significantly for days
  • It has no effect on corneal sensitivity

Correct Answer: It may transiently affect tear film and corneal reflexes, potentially altering some diagnostic tests

Q26. Which receptor or ion channel is the direct molecular target of benoxinate?

  • L-type calcium channels
  • Voltage-gated sodium channels in nerve membranes
  • Nicotinic acetylcholine receptors
  • Histamine H1 receptors

Correct Answer: Voltage-gated sodium channels in nerve membranes

Q27. Which is the best counseling point for a patient after receiving benoxinate eye drops?

  • Drive immediately; vision is unchanged
  • Avoid touching or rubbing the eye and expect temporary numbness and blurred vision
  • Apply warm compresses hourly for 48 hours
  • Start systemic antibiotics prophylactically

Correct Answer: Avoid touching or rubbing the eye and expect temporary numbness and blurred vision

Q28. Which of the following explains allergic reactions to ester local anesthetics like benoxinate?

  • Direct histamine release unrelated to metabolism
  • Immunologic response to PABA metabolites generated by ester hydrolysis
  • Activation of complement cascade by the parent drug only
  • IgG-mediated cytotoxicity against corneal cells

Correct Answer: Immunologic response to PABA metabolites generated by ester hydrolysis

Q29. For compounding or dispensing benoxinate ophthalmic drops, which practice is essential?

  • Use high ethanol concentration as solvent
  • Ensure sterile technique and preservative considerations appropriate for ophthalmic use
  • Store at room temperature and expose to direct sunlight
  • Label as for systemic injection use

Correct Answer: Ensure sterile technique and preservative considerations appropriate for ophthalmic use

Q30. Which experimental factor would most likely prolong benoxinate’s duration of action on the ocular surface?

  • Co-administration of esterases to the ocular surface
  • Formulation with a mucoadhesive vehicle that increases corneal contact time
  • Increasing tear turnover to wash the drug away faster
  • Using a lower pH that inactivates the drug

Correct Answer: Formulation with a mucoadhesive vehicle that increases corneal contact time

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