Lidocaine hydrochloride MCQs With Answer

Lidocaine hydrochloride MCQs With Answer

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Lidocaine hydrochloride MCQs With Answer provides B. Pharm students a focused, clinically relevant review of lidocaine hydrochloride — an amide‑type local anesthetic and class IB antiarrhythmic. This introduction covers mechanism of action (voltage‑gated sodium channel blockade), pharmacokinetics (hepatic metabolism via CYP enzymes), pharmacodynamics (onset, potency, duration), clinical uses (local infiltration, nerve block, topical, IV for ventricular arrhythmias), dosing limits, toxicity (CNS and cardiovascular signs) and management (including lipid emulsion therapy). Keywords: lidocaine hydrochloride, local anesthetic, amide, mechanism, metabolism, pharmacokinetics, toxicity, dose, epinephrine, antiarrhythmic, LAST. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which chemical class does lidocaine hydrochloride belong to?

  • Ester‑type local anesthetic
  • Amide‑type local anesthetic
  • Alkaloid analgesic
  • Sulfonamide antibiotic

Correct Answer: Amide‑type local anesthetic

Q2. What is the approximate pKa of lidocaine that influences its onset of action?

  • 6.5
  • 7.9
  • 8.9
  • 10.2

Correct Answer: 7.9

Q3. What is the primary mechanism of action of lidocaine on nerve fibers?

  • Activation of potassium channels
  • Blockade of voltage‑gated sodium channels
  • Inhibition of GABA receptors
  • Agonism at opioid receptors

Correct Answer: Blockade of voltage‑gated sodium channels

Q4. Which factor most directly speeds the clinical onset of lidocaine local anesthesia?

  • Higher protein binding
  • pKa closer to physiological pH (7.4)
  • Increased molecular weight
  • Lower lipid solubility

Correct Answer: pKa closer to physiological pH (7.4)

Q5. Lipid solubility of a local anesthetic primarily correlates with which property?

  • Onset of action
  • Potency
  • Water solubility
  • Renal clearance

Correct Answer: Potency

Q6. How is lidocaine mainly metabolized in the body?

  • Renal excretion as unchanged drug
  • Hepatic metabolism via CYP enzymes (e.g., CYP1A2, CYP3A4)
  • Hydrolysis by plasma esterases
  • Oxidation by intestinal bacteria

Correct Answer: Hepatic metabolism via CYP enzymes (e.g., CYP1A2, CYP3A4)

Q7. A principal active metabolite of lidocaine produced in the liver is:

  • Benzocaine
  • Monoethylglycinexylidide (MEGX)
  • Prilocaine
  • Para‑aminobenzoic acid (PABA)

Correct Answer: Monoethylglycinexylidide (MEGX)

Q8. What is the commonly quoted maximum recommended dose of lidocaine without epinephrine for adults?

  • 2 mg/kg (up to 100 mg)
  • 4.5 mg/kg (up to ~300 mg)
  • 6 mg/kg (up to 400 mg)
  • 10 mg/kg (no upper limit)

Correct Answer: 4.5 mg/kg (up to ~300 mg)

Q9. Adding epinephrine to lidocaine affects systemic absorption and duration how?

  • Increases systemic absorption and shortens duration
  • No change in absorption or duration
  • Decreases systemic absorption and prolongs duration
  • Makes lidocaine inactive

Correct Answer: Decreases systemic absorption and prolongs duration

Q10. Lidocaine is classified in antiarrhythmic therapy as which Vaughan‑Williams class?

  • Class IA
  • Class IB
  • Class IC
  • Class II

Correct Answer: Class IB

Q11. For which cardiac condition is IV lidocaine most appropriately used?

  • Supraventricular tachycardia due to AV nodal reentry
  • Atrial fibrillation with rapid ventricular response
  • Acute ventricular arrhythmias, especially ischemic ventricular ectopy
  • Bradycardia due to sinus node dysfunction

Correct Answer: Acute ventricular arrhythmias, especially ischemic ventricular ectopy

Q12. Early central nervous system signs of lidocaine systemic toxicity typically include:

  • Bradycardia and heart block
  • Hypoesthesia of the toes only
  • Tinnitus, perioral numbness, metallic taste and possible seizures
  • Hyperglycemia and polyuria

Correct Answer: Tinnitus, perioral numbness, metallic taste and possible seizures

Q13. The recommended immediate specific therapy for severe local anesthetic systemic toxicity (LAST) is:

  • Intravenous lipid emulsion therapy
  • High‑dose insulin only
  • Activated charcoal
  • Oral benzodiazepines

Correct Answer: Intravenous lipid emulsion therapy

Q14. Tissue acidosis around inflamed or infected areas affects lidocaine how?

  • Increases the unionized fraction and enhances block
  • Has no effect on lidocaine action
  • Shifts equilibrium toward ionized form, reducing membrane penetration and efficacy
  • Converts lidocaine to an ester‑type anesthetic

Correct Answer: Shifts equilibrium toward ionized form, reducing membrane penetration and efficacy

Q15. Alkalinization of lidocaine with bicarbonate is used clinically to:

  • Prolong duration indefinitely
  • Reduce potency
  • Speed onset by increasing the unionized fraction
  • Prevent hepatic metabolism

Correct Answer: Speed onset by increasing the unionized fraction

Q16. Compared with bupivacaine, lidocaine is generally:

  • More cardiotoxic
  • Less cardiotoxic with shorter duration
  • More protein bound and longer acting
  • An ester‑type local anesthetic

Correct Answer: Less cardiotoxic with shorter duration

Q17. Which statement about lidocaine protein binding is correct?

  • Lidocaine has higher protein binding than bupivacaine
  • Lidocaine has lower protein binding than bupivacaine
  • Lidocaine is not protein bound at all
  • Protein binding does not affect duration of action

Correct Answer: Lidocaine has lower protein binding than bupivacaine

Q18. Epinephrine‑containing lidocaine solutions are traditionally avoided in end‑artery sites because:

  • Epinephrine causes systemic hypertension only
  • Vasoconstriction may risk ischemia in end‑artery tissues (fingers, toes, penis, ear)
  • They are ineffective in these sites
  • Epinephrine increases local infection risk

Correct Answer: Vasoconstriction may risk ischemia in end‑artery tissues (fingers, toes, penis, ear)

Q19. The elimination half‑life of lidocaine in healthy adults is approximately:

  • 10–20 minutes
  • 1.5–2 hours
  • 8–12 hours
  • 24–48 hours

Correct Answer: 1.5–2 hours

Q20. Which topical preparation contains lidocaine used for skin anesthesia?

  • EMLA cream (lidocaine + prilocaine)
  • Silver sulfadiazine
  • Hydrocortisone ointment
  • Benzathine penicillin

Correct Answer: EMLA cream (lidocaine + prilocaine)

Q21. The form of lidocaine that most readily crosses neuronal membranes is:

  • The ionized (charged) form
  • The unionized (uncharged) form
  • The protein‑bound form
  • Lidocaine cannot cross membranes

Correct Answer: The unionized (uncharged) form

Q22. Lidocaine hydrochloride solutions are least stable under which condition?

  • Acidic pH
  • Alkaline pH
  • Refrigeration
  • Protected from light

Correct Answer: Alkaline pH

Q23. Regarding pregnancy and placental transfer, lidocaine:

  • Does not cross the placenta at all
  • Crosses the placenta and should be used with clinical caution
  • Is completely safe with no fetal effects
  • Is converted to an inert metabolite in the placenta

Correct Answer: Crosses the placenta and should be used with clinical caution

Q24. Lidocaine used for epidural or spinal anesthesia is characterized by:

  • Very long duration (over 8 hours)
  • Intermediate onset and duration compared with other local anesthetics
  • No sensory blockade, only motor blockade
  • Exclusively topical use, not for regional blocks

Correct Answer: Intermediate onset and duration compared with other local anesthetics

Q25. Which drug interaction is known to increase plasma lidocaine concentrations by inhibiting metabolism?

  • Rifampin
  • Cimetidine
  • Phenobarbital
  • Carbamazepine

Correct Answer: Cimetidine

Q26. Lidocaine exhibits use‑dependent blockade of sodium channels. This means:

  • Block is stronger at lower nerve firing rates
  • Block preferentially affects rapidly firing or depolarized fibers
  • Block is irreversible after a single dose
  • Lidocaine only blocks resting channels

Correct Answer: Block preferentially affects rapidly firing or depolarized fibers

Q27. The primary organ responsible for lidocaine clearance is the:

  • Liver
  • Kidney (unchanged excretion)
  • Lungs
  • Spleen

Correct Answer: Liver

Q28. In terms of action potential effects in cardiac tissue, lidocaine typically:

  • Prolongs action potential duration markedly (like class III agents)
  • Shortens action potential duration in ventricular tissue (class IB effect)
  • Has no electrophysiological effects
  • Acts as a beta‑adrenergic agonist

Correct Answer: Shortens action potential duration in ventricular tissue (class IB effect)

Q29. Which clinical route is NOT commonly used for lidocaine administration?

  • Topical application
  • Local infiltration or nerve block
  • Intravenous infusion for ventricular arrhythmias
  • Oral tablet formulation for systemic analgesia

Correct Answer: Oral tablet formulation for systemic analgesia

Q30. Adding epinephrine to lidocaine solutions typically does which of the following to peak plasma levels?

  • Increases peak plasma concentration
  • Has no effect on plasma concentration
  • Reduces peak plasma concentration by vasoconstriction
  • Eliminates systemic absorption entirely

Correct Answer: Reduces peak plasma concentration by vasoconstriction

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