Local Anesthetics MCQ Quiz | ANS & Peripheral NS

Welcome to the Local Anesthetics MCQ Quiz, designed for MBBS students preparing for their pharmacology exams. This quiz covers essential concepts from the Autonomic & Peripheral Nervous System syllabus. You will be tested on the mechanism of action, classification, pharmacokinetics, clinical applications, and toxicity of various local anesthetic agents. This assessment consists of 25 multiple-choice questions to help you evaluate your understanding and identify areas for improvement. After submitting your answers, you will see your score and a detailed review of each question. For your convenience and future revision, you can download a PDF file containing all the questions and their correct answers by clicking the download button. Good luck!

1. Which ion channel do local anesthetics primarily block to prevent nerve impulse conduction?

Voltage-gated potassium channelsVoltage-gated sodium channelsVoltage-gated calcium channelsLigand-gated chloride channels

2. Which of the following is an ester-linked local anesthetic?

LidocaineBupivacaineRopivacaineProcaine

3. How are amide-linked local anesthetics, such as lidocaine, primarily metabolized?

By plasma pseudocholinesterasesBy hepatic microsomal enzymes (CYP450)Renal excretion in unchanged formHydrolysis in the cerebrospinal fluid

4. Allergic reactions are more common with which class of local anesthetics?

Amides, due to their stable linkageEsters, due to their metabolite para-aminobenzoic acid (PABA)Both classes equallyThioesters

5. The phenomenon where local anesthetics bind more effectively to sodium channels that are frequently opening is known as:

TachyphylaxisState-dependenceUse-dependencePhase II block

6. The onset of action of a local anesthetic is hastened by:

High pKa of the drug and low pH of the tissueLow pKa of the drug and high pH of the tissueHigh lipid solubilityHigh protein binding

7. The most serious systemic toxicity with high plasma concentrations of local anesthetics like bupivacaine involves which two systems?

Renal and Hematologic systemsGastrointestinal and Musculoskeletal systemsCentral Nervous System (CNS) and Cardiovascular System (CVS)Endocrine and Respiratory systems

8. Why is epinephrine often added to local anesthetic solutions?

To increase the pH of the solutionTo directly anesthetize the nerve endingsTo decrease systemic absorption and prolong the duration of actionTo prevent allergic reactions

9. Local anesthetics tend to block different nerve fiber types at different rates. Which fibers are typically blocked first?

Large, myelinated A-alpha fibers (motor function)Small, unmyelinated C fibers (dull pain, temperature)Heavily myelinated A-beta fibers (touch, pressure)All fibers are blocked simultaneously

10. Which local anesthetic is known for its high potency, long duration of action, but also a significant risk of cardiotoxicity?

LidocaineProcaineBupivacaineMepivacaine

11. EMLA cream, a topical anesthetic, is a eutectic mixture of which two local anesthetics?

Procaine and TetracaineLidocaine and PrilocaineBupivacaine and RopivacaineCocaine and Benzocaine

12. A unique adverse effect associated with high doses of prilocaine is:

Malignant hyperthermiaMethemoglobinemiaAgranulocytosisTorsades de pointes

13. Which is the only local anesthetic that possesses intrinsic vasoconstrictive properties?

LidocaineTetracaineCocaineBupivacaine

14. The duration of action of a local anesthetic is most closely correlated with its:

pKaMolecular weightDegree of protein bindingWater solubility

15. Which property is most desirable for a local anesthetic used in spinal anesthesia to control the spread of the block?

Low lipid solubilityHigh pKaBaricity (density relative to CSF)Rapid metabolism in CSF

16. What is the recommended first-line treatment for Local Anesthetic Systemic Toxicity (LAST), especially severe cardiotoxicity?

Intravenous sodium bicarbonateIntravenous lipid emulsion therapyIntravenous calcium gluconateHigh-dose epinephrine

17. Which of these is almost exclusively used as a topical anesthetic due to its poor solubility and high risk of systemic toxicity if injected?

LidocaineRopivacaineBenzocaineMepivacaine

18. In an infected (acidic) tissue, the efficacy of a local anesthetic is reduced. This is primarily because:

The drug is rapidly metabolized by bacterial enzymes.A higher proportion of the anesthetic exists in its ionized, cationic form, which cannot cross the nerve membrane.The acidic environment enhances systemic absorption.Infected tissues have increased blood flow, washing the anesthetic away.

19. Which local anesthetic was developed as a safer alternative to bupivacaine, with a similar profile but lower cardiotoxicity?

PrilocaineTetracaineRopivacaineArticaine

20. The metabolite responsible for hypersensitivity reactions to ester-type local anesthetics is:

Monoethylglycine xylidide (MEGX)Glycine xylidide (GX)Para-aminobenzoic acid (PABA)O-toluidine

21. Local anesthetics are formulated as acidic salts (e.g., lidocaine hydrochloride) to increase stability and water solubility. Why?

The acidic form is the active form that blocks the channel.The base form is unstable and degrades quickly in solution.The base form is poorly water-soluble and would precipitate.The acidic form prevents bacterial contamination.

22. Which statement correctly describes the relationship between nerve fiber size and sensitivity to local anesthetic block?

Larger, myelinated fibers are more sensitive than smaller, unmyelinated fibers.Smaller, myelinated fibers (A-delta) are generally more sensitive than small, unmyelinated fibers (C).Fiber size has no impact on the sensitivity to local anesthetics.All myelinated fibers are blocked before any unmyelinated fibers.

23. Among the commonly used injectable local anesthetics, which one has the shortest duration of action without a vasoconstrictor?

BupivacaineLidocaineProcaineRopivacaine

24. What structural feature of Articaine contributes to its rapid metabolism and lower systemic toxicity risk?

It contains a thiophene ring instead of a benzene ring.It is a pure S-enantiomer.It has an additional ester group that is rapidly hydrolyzed by plasma esterases.It has the lowest pKa of all amides.

25. Which of the following is typically an early sign of Central Nervous System (CNS) toxicity from local anesthetics?

Respiratory depressionComaPerioral numbness and metallic tasteBradycardia

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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