Prilocaine MCQs With Answer

Prilocaine MCQs With Answer
Prilocaine is an amide-type local anesthetic commonly used for infiltration, nerve block and topical anesthesia. B. Pharm students must master its mechanism of action, physicochemical properties (pKa, lipid solubility, protein binding), pharmacokinetics, and hepatic metabolism to o‑toluidine — the metabolite linked to methemoglobinemia. This focused set explores clinical uses, adverse effects, interactions, monitoring parameters, emergency management (methylene blue, lipid emulsion), and comparisons with lidocaine and bupivacaine. Questions are designed for exam preparation and practical understanding, emphasizing safe dosing, patient risk factors, and signs of systemic toxicity. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which is the primary mechanism of action of prilocaine?

• Inhibition of acetylcholinesterase
• Blockade of voltage-gated sodium channels
• Activation of GABA-A receptors
• Blockade of NMDA receptors

Correct Answer: Blockade of voltage-gated sodium channels

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

• Esters
• Amides
• Ketones
• Sulfonamides

Correct Answer: Amides

Q3. Which metabolite of prilocaine is chiefly responsible for methemoglobinemia?

• Para-aminobenzoic acid (PABA)
• o-Toluidine
• p-Nitroaniline
• Acetaminophen

Correct Answer: o-Toluidine

Q4. Which topical preparation combines prilocaine for dermal anesthesia commonly used in pediatrics?

• Epinephrine gel
• EMLA cream
• Tetracaine ointment
• Procaine spray

Correct Answer: EMLA cream

Q5. Compared with bupivacaine, prilocaine is best characterized as:

• More cardiotoxic and longer acting
• Less cardiotoxic and shorter acting
• An ester-type with longer duration
• Only suitable for spinal anesthesia

Correct Answer: Less cardiotoxic and shorter acting

Q6. Which clinical use is most appropriate for prilocaine?

• Long-term postoperative analgesia for major surgeries
• Short procedures requiring infiltration or regional block
• Chronic neuropathic pain management
• Systemic analgesia by oral administration

Correct Answer: Short procedures requiring infiltration or regional block

Q7. Which laboratory method gives the definitive measurement of methemoglobin levels?

• Standard pulse oximetry
• Arterial blood gas without co-oximetry
• Co-oximetry
• Complete blood count

Correct Answer: Co-oximetry

Q8. Which sign is an early indicator of systemic local anesthetic toxicity?

• Profound hypotension without central symptoms
• Perioral numbness, tinnitus and metallic taste
• Delayed wound healing
• Bradycardia preceding seizures

Correct Answer: Perioral numbness, tinnitus and metallic taste

Q9. The recommended first-line treatment for clinically significant methemoglobinemia caused by prilocaine is:

• Intravenous naloxone
• High-dose vitamin C
• Methylene blue
• Activated charcoal

Correct Answer: Methylene blue

Q10. Risk of methemoglobinemia with prilocaine is particularly high in which patient group?

• Adults on beta-blockers
• Infants under 3 months of age
• Patients with hypertension controlled by ACE inhibitors
• Patients with hyperthyroidism

Correct Answer: Infants under 3 months of age

Q11. Which factor most directly determines the onset of action of prilocaine?

• Protein binding percentage
• pKa relative to tissue pH
• Renal clearance
• Manufacturing brand

Correct Answer: pKa relative to tissue pH

Q12. Combining prilocaine with epinephrine typically results in:

• Increased systemic absorption and shorter duration
• No change in pharmacokinetics
• Decreased systemic absorption and prolonged duration
• Immediate inactivation of prilocaine

Correct Answer: Decreased systemic absorption and prolonged duration

Q13. Which enzyme system primarily metabolizes prilocaine?

• Plasma and hepatic amidases
• CYP3A4 exclusively
• CYP2D6 exclusively
• Monoamine oxidase

Correct Answer: Plasma and hepatic amidases

Q14. Prilocaine is less effective in infected tissues because:

• Infection increases local lipid solubility
• Acidic pH reduces the fraction of un-ionized drug
• Inflammation increases binding to sodium channels
• Infection converts prilocaine into inactive esters

Correct Answer: Acidic pH reduces the fraction of un-ionized drug

Q15. Which drug interaction increases the risk of methemoglobinemia when used with prilocaine?

• Probenecid
• Dapsone
• Amoxicillin
• Metformin

Correct Answer: Dapsone

Q16. Which statement about prilocaine’s cardiovascular toxicity is correct?

• It has higher cardiotoxic potential than bupivacaine
• Cardiotoxicity is negligible and never clinically relevant
• Cardiotoxic effects are dose-related and less than bupivacaine
• It causes irreversible myocardial necrosis at therapeutic doses

Correct Answer: Cardiotoxic effects are dose-related and less than bupivacaine

Q17. Which is a common dental application of prilocaine?

• Systemic analgesia for toothache
• Local infiltration and inferior alveolar nerve block
• Antimicrobial mouthwash
• Salivary stimulation

Correct Answer: Local infiltration and inferior alveolar nerve block

Q18. Which monitoring is most important immediately after administering a large dose of prilocaine?

• Blood glucose measurement
• Continuous cardiac and respiratory monitoring with pulse oximetry
• Serum creatinine only
• 24-hour liver function tests

Correct Answer: Continuous cardiac and respiratory monitoring with pulse oximetry

Q19. Which clinical feature best suggests methemoglobinemia rather than hypoxemia from respiratory failure?

• Rapid improvement with supplemental oxygen alone
• Pulse oximetry reading around 85% despite oxygen therapy
• Marked hypercapnia on arterial blood gas
• Wheezing and bronchospasm

Correct Answer: Pulse oximetry reading around 85% despite oxygen therapy

Q20. Prilocaine produces local anesthesia by preferentially binding to which state of the sodium channel?

• Resting (closed) state only
• Open and inactivated states more than resting
• Only to extracellular ligand sites
• Only to potassium channels

Correct Answer: Open and inactivated states more than resting

Q21. Which emergency therapy is recommended for severe systemic local anesthetic cardiovascular toxicity?

• Intravenous lipid emulsion therapy
• Oral charcoal
• Topical vasoconstrictor application
• Subcutaneous epinephrine only

Correct Answer: Intravenous lipid emulsion therapy

Q22. Which adverse reaction is more specifically associated with prilocaine than with many other amide anesthetics?

• High incidence of anaphylaxis
• Methemoglobinemia due to o‑toluidine
• Permanent renal failure
• Severe asthma exacerbation

Correct Answer: Methemoglobinemia due to o‑toluidine

Q23. Which statement is true regarding protein binding and duration of action for local anesthetics like prilocaine?

• Higher protein binding generally leads to shorter duration
• Protein binding does not affect duration of action
• Higher protein binding generally contributes to longer duration
• Protein binding causes immediate inactivation

Correct Answer: Higher protein binding generally contributes to longer duration

Q24. Which of the following conditions is a contraindication or warrants extreme caution with prilocaine use?

• Hereditary methemoglobinemia or severe anemia
• Controlled seasonal allergic rhinitis
• Well-managed osteoarthritis
• Hyperlipidemia on statin therapy

Correct Answer: Hereditary methemoglobinemia or severe anemia

Q25. Compared to lidocaine, prilocaine is generally described as:

• More vasodilatory and shorter acting than lidocaine
• Less vasodilatory with similar onset and slightly shorter or comparable duration
• Identical in all pharmacological properties
• Only available as an ester derivative

Correct Answer: Less vasodilatory with similar onset and slightly shorter or comparable duration

Q26. Which clinical approach reduces the risk of systemic toxicity when giving regional prilocaine injections?

• Injecting rapidly into an intravascular location
• Using the smallest effective dose and aspirating before injection
• Always combining with high-dose systemic opioid
• Avoiding the use of any vasoconstrictor

Correct Answer: Using the smallest effective dose and aspirating before injection

Q27. Which bedside sign should alert a clinician to suspect methemoglobinemia after prilocaine administration?

• Bright red arterial blood that does not change color on exposure to air
• Chocolate-brown colored blood and persistent cyanosis despite oxygen
• Profuse bleeding from the injection site
• Marked hyperthermia above 40°C

Correct Answer: Chocolate-brown colored blood and persistent cyanosis despite oxygen

Q28. Which pharmacokinetic property explains why prilocaine effects are terminated by metabolism rather than renal excretion of unchanged drug?

• Extensive hepatic and plasma amidase metabolism
• Complete excretion as unchanged drug in urine
• High molecular weight preventing metabolism
• Exclusive biliary elimination of intact prilocaine

Correct Answer: Extensive hepatic and plasma amidase metabolism

Q29. For seizure activity resulting from systemic local anesthetic toxicity, the recommended immediate pharmacologic treatment is:

• Benzodiazepines (e.g., midazolam)
• High-dose insulin infusion
• Long-acting barbiturate infusion only
• Oral antiepileptics alone

Correct Answer: Benzodiazepines (e.g., midazolam)

Q30. EMLA cream contains which concentrations of lidocaine and prilocaine?

• 5% lidocaine and 0% prilocaine
• 2.5% lidocaine and 2.5% prilocaine
• 1% lidocaine and 4% prilocaine
• 0.5% lidocaine and 0.5% prilocaine

Correct Answer: 2.5% lidocaine and 2.5% prilocaine

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