Local Anaesthesia Question and Answers

Local Anaesthesia Important Notes

Local Anaesthesia Classification:

1. Based on the Site of Action:

  • Class A: Agents acting on the Exampleternal surface of the membrane: Example- Biotoxins
  • Class B: Agents acting on the internal surface of the membrane. Example- Quaternary ammonium compounds
  • Class C- Agents acting by independent mechanism- Example- Benzocaine
  • Class D- Agents acting by combination mechanisms- Example- Articaine, Bupivacaine

2. Based On Group of Drugs:


Esters of Benzoic Acids:

    • Butacaine
    • Cocaine
    • HExampleylcaine
    • Tetracaine

Esters of Paraamino Acids:

    • Chloroquine
    • Procaine
    • Atricaine
    • Bupivacaine
    • Etidocaine
  • Quinolone- Centbucridine

Local Anaesthesia Parts:

  • Aromatic lipophilic group
  • Hydrophilic amino group
  • An intermediate chain

Local Anaesthesia Biotransformation:

  • Ester group – hydrolysis by plasma cholinesterases
  • Amide group – hydrolysis and hydroxylation by microsomal enzymes of the liver

Local Anaesthesia Safe dose:

  • A safe dose of 2% lignocaine is
    • 4.5 mg/kg or 300 mg without vasoconstrictor
    • 7 mg/kg or 500 mg with vasoconstrictor
  • Safely dose of adrenaline for dental use
    • In normal patients – 0.2 mg
    • For cardiac patients – 0,04 mg

Safe dose Actions:

  • Anaesthesia of smaller nerve fibres
  • Stimulation of CNS
  • Produces vasodilatation
  • Produces depressant effect on the myocardium

Read And Learn More: Pharmacology Question and Answers

Local Anaesthesia Adverse drug reactions:

  • Intolerance
  • Cardiovascular depression
  • CNS stimulation
  • CNS depression
  • Malignant hyperpyrExampleia

Local Anaesthesia Uses:

  • Surface anaesthesia – for pain due to burns, ulcers and fissures
  • Infiltration anaesthesia
  • Nerve block anaesthesia
  • Spinal anaesthesia
  • Systemic use for anti-arrhythmic effect

Local Anaesthesia Long Essays

Question 1. Classify local anaesthetics and write in detail about xylocaine/lignocaine.


Local Anaesthetics:

Local anaesthetics are drugs which cause a reversible loss of sensation in the restricted area of the body either by depression in the Excitation of conducting nerves or suppression of Examplecitation of peripheral nerves.

Local Anaesthetics Classification:

1. Based on chemical structure.

  • Amides – Lignocaine, mepivacaine.
  • Esters.
    • Esters of benzoic acid – Butaaine, cocaine.
    • Esters of para-aminobenzoic acid – chloride- caine.
  • Quinolones – Centbucridine.

2. Based on the duration of action.

  • Injectable anaesthetics.
    • Low potency and short duration,
      • Procaine, chlorprocain.
    • Intermediate potency and duration.
      • Lignocaine and prilocaine.
    • High potency and long duration.
      • Tetracaine, bupivacaine.
  • Surface anaesthetic.
    • Soluble – cocaine, lignocaine, tetracaine.
    • Insoluble – benzocaine, tetracaine.

3. Based on biological site and mode of action.

  • Class A
    • Agents acting at receptor site on Exampleternal surface of nerve membrane.
      • Example: biotoxin.
  • Class B.
    • Agents act at receptor sites on the internal surface of the nerve membrane.
      • Example: quaternary ammonium compounds.
  • Class C.
    • Agents act by a receptor-independent physical-chemical mechanism.
      • Example: Benzocaine.
  • Class D.
    • Agents act by a combination of receptor and receptor-independent mechanisms.
      • Examples: Atricaine, lidocaine, mepivacaine.

Local Anaesthetics Mechanism of Action:

Displacement of calcium ions from sodium channel receptor site which permits.

The binding of the LA molecule to this site produces.

Blockade of the sodium channel and decrease in sodium conductance.

Leads to depression in the rate of electrical depolarization.

Failure to achieve the threshold potential level along with.

Lack of development of propagated action potential called.

Conduction Blockade


  • It is the most widely used local anaesthesia.
  • It is fast and long-lasting.
  • It blocks nerve conduction within 3 min.

Xylocaine/Llgnocaine Actions:

1. Local actions:

  • Blocks sensory nerve endings, nerve trunk, neuromuscular junction, ganglionic synapse and receptors.
  • Reduces the release of acetylcholine.
  • Causes anaesthesia of the skin and paralysis of voluntary muscles.

2. Systemic actions.

  • CNS [Central Nervous System]
    • Produces stimulation followed by depression.
    • Causes blood-brain barrier (BBB).
    • Depresses cortical inhibitory pathway.
  • Cardiovascular system (CVS).
    • Lignocaine decreases Examplecitability, conduction rate and force of contraction.
    • Causes hypotension due to vasodilatation and myocardial depression.
  • Smooth muscles
    • Depresses contraction of intact bowel.

Xylocaine/Llgnocaine Uses:

1. Anaesthesia.

  • Used in all types of anaesthesia.

2. Anti-arrhythmia.

Xylocaine/Llgnocaine Adverse Effects:

1. CNS effects.

  • Drowsiness, mental clouding, altered tastes, tinnitus.

2. CVS effects.

  • Hypotension, bradycardia, cardiac arrhythmia, vascular collapse.

3. Overdose.

  • Causes muscle twitching, convulsions, and cardiac arrhythmia.

4. Injections are painful and may delay wound healing.

Question 2. Mention the types of local anaesthetics.


Types of Methods of Local Anaesthesia:

Types Of Methods Of Local Anaesthesia

Question 3. Classify local anaesthetics. Compare lignocaine and cocaine.


local anaesthetics Classification:

Compare Lignocaine And Cocaine

Question 4. Explain how the action of lignocaine can be prolonged.


Prolonging Action of Lignocaine:

  • The action of lignocaine can be prolonged by the addition of adrenaline.
  • Adrenaline reduces the rate of absorption of lignocaine from the site to systemic circulation.
  • This prolongs the duration of the action.
  • It also reduces the systemic toxicity of lignocaine because of its slow absorption.
  • As it gets absorbed, it is metabolized.

Question 5. Write a note on the advantages of lignocaine.


lignocaine Advantages:

  • Most widely used.
  • Versatile, used for all types of blocks.
  • Fast and long-lasting.
  • Blocks nerve conduction within 3 min.
  • More intense.
  • Its effect last for 30 – 45 min.
  • Available in various forms like spray, gel ointment, and injection.
  • Cross sensitivity is not seen with it

Local Anaesthesia Short Essays

Question 1. Uses of adrenaline with lignocaine.
The rationale of combining adrenaline with Lignocaine.


Combining adrenaline with lignocaine has some advantages as well as disadvantages.

Lignocaine Advantages:

  • Decreases rate of absorption of lignocaine.
  • This prolongs its duration of action.
  • Reduces systemic toxicity.
  • Increases intensity of nerve block.
  • Provides a bloodless field for surgery.

Lignocaine Disadvantages:

  • Intense vasospasm and ischaemia in the tissues with end arteries cause gangrene.
  • Absorption of adrenaline may cause systemic toxicity.
  • It may delay wound healing.

Lignocaine Contraindications:

  • The adrenaline + lignocaine combination is contraindicated in
  • Cardiovascular disorders.
  • Hypertension.
  • Congestive cardiac failure.
  • Ischaemic heart disease.

Question 2. Differentiate between general anaesthesia and local anaesthesia.


Difference Between General Anaesthesia And Local Anaesthesia

Question 3. Techniques of local anaesthesia with examples


Techniques Of Local Anaesthesia With Example

Local Anaesthesia Short Answers

Question 1. Lidocaine/Lignocaine/xylocain.


Lidocaine is a long-lasting amide local anaesthetic agent.

  • It is the most widely used local anaesthetic.
  • It causes vasodilation in the area of injection.
  • It is used in all types of blocks.
  • It is available in various forms.
  • Its effects occur within 3 min and last for 30 – 45 min.
  • Its action can be prolonged by the addition of adrenaline.
  • It is metabolized in the liver.
  • It is used in 0.5 – 2% concentration.

Question 2. Cocaine.


Cocaine is a natural alkaloid obtained from leaves of Erythroxylon coca.

  • It is an ester local anaesthetic agent.
  • Earlier it was used for ocular anaesthesia.
  • It is well observed.
  • As it is a protoplasmic poison, it is never injected.
  • In the periphery, it blocks noradrenaline and adrenaline into adrenergic nerve endings.
  • It causes.
  1. Local vasoconstriction.
  2. Tachycardia.
  3. Rise in BP.
  4. Mydriasis.

Question 3. Procaine.


It is an ester local anaesthetic agent.

  • It is the first synthetic local anaesthetic.
  • It is metabolized in plasma.
  • It is not surface anaesthetic.

Procaine Mechanism:

Hydrolysis of procaine.

Release of para-aminobenzoic acid (PABA)

This antagonises the antibacterial action of sulphonamide.

Question 4. Topical local anaesthetics.


  • Also known as surface anaesthetics.
  • They are available as solutions, ointments, gels, creams, sprays, lozenges, etc.

Topical local anaesthetics Drugs used:

Drugs Used

Topical local anaesthetics Uses:

  • Applied topically on the mucous membrane of the nose, mouth, eyes, throat, upper respiratory tract, oesophagus, and urethra.
  • During endoscopy
  • In tonometry of eye.

Question 5. Intravenous anaesthesia.


Also known as Bier’s block.

  • It allows an extremely rapid induction.
  • There is no route of quick elimination like lungs for it
  • Thus it is used for induction.
  • During it, anaesthesia is maintained by an inhalational agentIntravenous Anaesthesia

Question 6. Lidocain and mepivacaine.


Lidocain And Mepivacaine


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