Propoxycaine MCQs With Answer

Introduction:

Propoxycaine MCQs With Answer is a focused revision set for B. Pharm students covering propoxycaine’s pharmacology, mechanism, pharmacokinetics, metabolism, clinical uses and adverse effects. These questions emphasize key concepts: classification as an ester local anesthetic, sodium‑channel blockade, structure‑activity relationships, factors affecting onset and duration (pKa, lipid solubility, protein binding), plasma esterase metabolism, PABA‑related allergy risk, common ophthalmic and topical formulations, and management of systemic toxicity. Ideal for exam prep, practical understanding and clinical pharmacology discussions, this set reinforces drug interactions, contraindications and safe administration principles. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary pharmacological classification of propoxycaine?

• An ester local anesthetic
• An amide local anesthetic
• A general anesthetic
• A neuromuscular blocker

Correct Answer: An ester local anesthetic

Q2. What is the main mechanism of action of propoxycaine?

• Enhancement of GABAergic inhibition
• Blockade of voltage‑gated sodium channels
• Activation of opioid receptors
• Inhibition of acetylcholinesterase

Correct Answer: Blockade of voltage‑gated sodium channels

Q3. Which structural feature is characteristic of local anesthetics like propoxycaine?

• Aromatic lipophilic ring, intermediate ester linkage, tertiary amine
• Steroid nucleus with hydroxyl groups
• Peptide chain with disulfide bonds
• Monoamine oxidase inhibitor scaffold

Correct Answer: Aromatic lipophilic ring, intermediate ester linkage, tertiary amine

Q4. How does lipid solubility affect propoxycaine’s properties?

• Higher lipid solubility increases potency and duration
• Higher lipid solubility decreases potency
• Lipid solubility only affects elimination, not potency
• It makes the drug ineffective topically

Correct Answer: Higher lipid solubility increases potency and duration

Q5. Which factor primarily determines the onset of action for propoxycaine?

• pKa relative to physiological pH
• Renal clearance
• Presence of sulfate ions in formulation
• Metabolism by cytochrome P450

Correct Answer: pKa relative to physiological pH

Q6. Propoxycaine is mainly metabolized by which pathway?

• Plasma esterases (pseudocholinesterase)
• Hepatic cytochrome P450 oxidation
• Renal tubular secretion unchanged
• Glucuronidation in the gut

Correct Answer: Plasma esterases (pseudocholinesterase)

Q7. Which metabolic product risk is associated with ester local anesthetics like propoxycaine?

• Para‑aminobenzoic acid (PABA) derivatives causing allergy
• Accumulation of acyl glucuronides causing hepatotoxicity
• Formation of nitrosoamines causing mutagenicity
• Heavy metal chelation leading to nephrotoxicity

Correct Answer: Para‑aminobenzoic acid (PABA) derivatives causing allergy

Q8. What is a common clinical use of propoxycaine?

• Topical ophthalmic anesthesia for ocular procedures
• General anesthesia induction agent
• Systemic analgesic for chronic pain
• Long‑term epidural infusion for labor

Correct Answer: Topical ophthalmic anesthesia for ocular procedures

Q9. Addition of a vasoconstrictor (e.g., epinephrine) to a local anesthetic solution primarily does what?

• Reduces systemic absorption and prolongs local action
• Accelerates plasma ester hydrolysis
• Promotes conversion to active metabolite
• Directly antagonizes sodium channel blockade

Correct Answer: Reduces systemic absorption and prolongs local action

Q10. Which adverse effect is most characteristic of local anesthetic systemic toxicity (LAST)?

• CNS excitation followed by CNS depression and seizures
• Severe hypoglycemia without neurological signs
• Progressive renal failure within minutes
• Isolated peripheral neuropathy without central signs

Correct Answer: CNS excitation followed by CNS depression and seizures

Q11. Which sign indicates early cardiovascular toxicity from an overdose of propoxycaine?

• Arrhythmias and hypotension
• Brisk hypertension with tachycardia only
• Isolated increase in urine output
• Marked hyperreflexia in lower limbs

Correct Answer: Arrhythmias and hypotension

Q12. Why are ester local anesthetics more likely to cause allergic reactions than amides?

• They are metabolized to PABA, a known allergen
• They undergo enterohepatic recirculation causing immune response
• They bind irreversibly to plasma proteins
• They increase histamine release via mast cell lysis only

Correct Answer: They are metabolized to PABA, a known allergen

Q13. Which property influences duration of action of propoxycaine the most?

• Protein binding and lipid solubility
• Colour of the formulation
• Daily dietary intake of fat
• Ambient room temperature alone

Correct Answer: Protein binding and lipid solubility

Q14. In comparing propoxycaine to lidocaine, a likely difference is:

• Propoxycaine (ester) is metabolized faster by plasma esterases than lidocaine (amide)
• Propoxycaine is primarily metabolized by cytochrome P450 like lidocaine
• Propoxycaine cannot block sodium channels whereas lidocaine can
• Propoxycaine is used intravenously for systemic analgesia more than lidocaine

Correct Answer: Propoxycaine (ester) is metabolized faster by plasma esterases than lidocaine (amide)

Q15. Which clinical scenario is a relative contraindication to using propoxycaine topically?

• Known severe allergy to ester local anesthetics
• Mild seasonal allergic rhinitis without drug allergy
• Well‑controlled hypertension with no history of anesthesia reactions
• Uncomplicated refractive error correction

Correct Answer: Known severe allergy to ester local anesthetics

Q16. Which monitoring is essential after administering topical propoxycaine for ocular procedures?

• Observation for CNS symptoms and cardiovascular instability
• Hourly blood glucose for 24 hours
• Continuous dialysis for 12 hours
• Immediate arterial blood gas for all patients

Correct Answer: Observation for CNS symptoms and cardiovascular instability

Q17. Which statement about pKa and local anesthetic action is correct?

• Lower difference between drug pKa and tissue pH results in faster onset
• Higher pKa always guarantees longer duration
• pKa has no effect on onset or potency
• pKa only affects taste, not pharmacology

Correct Answer: Lower difference between drug pKa and tissue pH results in faster onset

Q18. What is the rationale for using the lowest effective concentration of propoxycaine?

• To minimize systemic absorption and toxicity while providing adequate local effect
• To enhance conversion to PABA and increase duration
• To accelerate renal excretion of the parent compound
• To ensure irreversible nerve blockade for prolonged anesthesia

Correct Answer: To minimize systemic absorption and toxicity while providing adequate local effect

Q19. Which drug is a recommended emergency treatment adjunct for severe local anesthetic cardiotoxicity?

• Intravenous lipid emulsion therapy
• High‑dose oral vitamin C
• Topical corticosteroid application
• Inhaled bronchodilator alone

Correct Answer: Intravenous lipid emulsion therapy

Q20. Which formulation is most commonly used for propoxycaine administration?

• Ophthalmic drops for topical anesthesia
• Oral tablets for systemic analgesia
• Intramuscular depot injections for long‑term pain
• Transdermal patches for chronic anesthesia

Correct Answer: Ophthalmic drops for topical anesthesia

Q21. Which interaction could increase systemic toxicity of propoxycaine?

• Concurrent use of other local anesthetics or drugs that decrease protein binding
• Administration with activated charcoal immediately after topical use
• Use with oral antacids at distant times
• Concomitant use of topical emollients only

Correct Answer: Concurrent use of other local anesthetics or drugs that decrease protein binding

Q22. Which property of inflamed or infected tissue affects local anesthetic efficacy?

• Lower pH reduces the fraction of nonionized drug, slowing onset and reducing potency
• Higher pH increases the ionized form making the drug more effective
• Inflammation enhances lipid solubility making the drug more potent
• Infection increases plasma esterases at the site making the drug last longer

Correct Answer: Lower pH reduces the fraction of nonionized drug, slowing onset and reducing potency

Q23. Which laboratory abnormality would you most likely monitor in a patient with suspected propoxycaine overdose?

• Arterial blood gases and cardiac rhythm monitoring rather than a single lab value
• Serum potassium to detect immediate hyperkalemia only
• Blood culture for bacterial contamination
• Fasting lipid panel immediately

Correct Answer: Arterial blood gases and cardiac rhythm monitoring rather than a single lab value

Q24. Which statement about placental transfer of local anesthetics is true?

• Most local anesthetics cross the placenta; fetal exposure depends on maternal dose and protein binding
• No local anesthetic crosses the placenta under any circumstance
• Only ester anesthetics cross while amides do not
• Placental transfer renders local anesthetics completely inactive

Correct Answer: Most local anesthetics cross the placenta; fetal exposure depends on maternal dose and protein binding

Q25. Which is an important point in compounding propoxycaine ophthalmic drops?

• Sterility and appropriate preservative choice to avoid ocular irritation
• Use of high alcohol content to increase solubility
• Addition of systemic anticoagulant for stability
• Heating to 80°C during preparation to sterilize

Correct Answer: Sterility and appropriate preservative choice to avoid ocular irritation

Q26. Which statement about allergic cross‑reactivity is correct?

• Patients allergic to one ester may react to other esters due to similar PABA metabolites
• Allergic reactions to esters automatically imply cross‑reactivity with all amides
• There is never any cross‑reactivity between different local anesthetics
• Only topical antihistamines cause cross‑reactivity, not anesthetics

Correct Answer: Patients allergic to one ester may react to other esters due to similar PABA metabolites

Q27. Which pharmacokinetic factor reduces systemic toxicity risk for propoxycaine?

• Rapid hydrolysis by plasma esterases leading to short systemic half‑life
• Poor absorption from all mucosal surfaces making it ineffective
• Complete renal excretion unchanged after topical use only
• Irreversible protein conjugation in blood

Correct Answer: Rapid hydrolysis by plasma esterases leading to short systemic half‑life

Q28. Which patient history would prompt extra caution before using propoxycaine?

• A history of severe allergic reaction to procaine or other ester anesthetics
• A history of well‑managed seasonal allergies to pollen
• Minor refractive errors corrected previously without anesthetic complications
• No prior surgery but good overall health

Correct Answer: A history of severe allergic reaction to procaine or other ester anesthetics

Q29. Which monitoring parameter is most useful immediately after inadvertent intravascular injection of propoxycaine?

• Continuous ECG monitoring for arrhythmias and blood pressure assessment
• Immediate complete urine analysis only
• Measurement of serum alkaline phosphatase alone
• Visual acuity test as the sole monitoring tool

Correct Answer: Continuous ECG monitoring for arrhythmias and blood pressure assessment

Q30. For teaching pharmacology, which comparison helps explain propoxycaine’s shorter systemic duration versus amide anesthetics?

• Esters are rapidly hydrolyzed by plasma esterases, while amides are metabolized hepatically
• Esters are stored in fat tissues making them longer acting than amides
• Amides always have shorter duration due to renal excretion
• Esters do not bind to sodium channels, explaining shorter action

Correct Answer: Esters are rapidly hydrolyzed by plasma esterases, while amides are metabolized hepatically

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