This document discusses local anesthetics and their uses and properties. It begins by outlining learning objectives for medical students regarding local anesthetics. It then classifies local anesthetics and discusses the mechanism of action. Individual compounds like cocaine, lignocaine, bupivacaine, benoxinate and oxethazaine are described. Uses of local anesthetics for surface anesthesia and injectable anesthesia are provided. The conclusion reiterates that local anesthetics cause reversible nerve conduction loss and bind to sodium channels, and their proper use depends on compound and safe dosing to avoid central nervous system effects.

1. Local Anaesthetics
Dr. Pravin Prasad
M.B.B.S., MD Clinical Pharmacology
Lecturer, Lumbini Medical College
31 July 2018 (15 Shrawan 2075),
Tuesday

2. At the end of the class, MBBS
Sem IV students will be able
to:
Review relevant physiology of pain (definition,
conducting pathways, fibres, channels and ions
involved)
Classify local anaesthetics (LA)
Explain the mechanism of action of LA
List the actions of LAs
Discuss the salient features of different LAs

3. Individual compounds:
Cocaine
Good surface anaesthetic
Causes psychological dependence
Reverse tolerance might be seen
Stimulates most of the centres
Blocks uptake of NA in peripheral adrenergic
nerves
Not used due to higher side effects

4. Individual compounds:
Lignocaine
Used as surface and injectable anaesthesia
Onset of action after injection- 3 minutes
Action more intense and longer lasting
Cross sensitivity with ester LA not seen
Early CNS effects- depressant
Overdose: muscle twitching, convulsions,
arrhythmia, coma, respiratory arrest

5. Individual compounds:
Bupivacaine
Used as injectable LA:
Infiltration, nerve block
Epidural and spinal anaesthesia of long
duration
Use:
Painless labour
Post-operative pain relief

6. Individual compounds
Benoxinate
Surface anaesthetic for eye
0.4% solution for tonometry
Benzocaine, Butylaminobenzoate
Not absorbed through mucous membrane or
abraded skin
Long lasting anaesthesia
Used as lozenges, dusting powder,

7. Individual compounds:
Oxethazaine
Topical anaesthetic
Very low ionisation seen even at low pH
Used to anaesthetise gastric mucosa
Overdose:
More than 100mg/day
Dizziness and drowsiness

8. Uses: Surface anaesthesia
Lozenges
Mouth wash
Spray
Cream

9. Uses: Injectable anaesthesia
Infiltration Anaesthesia
Conduction block
Spinal block
Epidural anaesthesia
Intravenous regional anaesthesia

10. Conclusion
Local Anaesthetics cause reversible loss of
nerve conduction
Used for diminishing pain sensation
LAs binds to voltage gated Na+ channels from
inner side
Prefers activated and inactivated state of the
channel

11. Conclusion
Sensitivity of nerves for LA differs
LAs chemically are of two types
Inadvertent high dose or accidental intra
venous infusion can lead to CNS and CVS
effects
Depending upon the agent, LAs can be used
topically and by injectable route
Oxethazine can be used to anaesthetise
gastric mucosa

12. That’s all for LA!
Question???