Local anesthetics work by reversibly blocking sodium channels in nerve cell membranes, preventing the propagation of action potentials and sensation. They are useful for minor procedures as they cause loss of sensation in a localized area without loss of consciousness. Common local anesthetics include lidocaine, bupivacaine, and procaine. Factors like lipid solubility and pH influence their onset and duration of action. While generally safe, local anesthetics can potentially cause adverse effects like numbness, seizures, or cardiac issues depending on the drug and dosage. Proper technique and patient health assessment are important considerations for safe use of local anesthesia.

1. Local Anesthetics
Dr Bikash Meher
MBBS,MD

2.  Definition of LA
 LA vs GA
 M.O.A
 P.K
 Systemic effects
 Adverse effects
 Individual LA
 Clinical application and technique
Out linesOut lines

3. Drugs which upon topical application or local injection cause
reversible loss of sensation, sensory or motor or both in a
localized area of the body without loss of consciousness.
Definition

4. LA Vs GA
General Local
Site of action CNS Peripheral nerves
Area Whole body Restricted areas
Consciousness Lost Unaltered
Preferential use Major surgery Minor surgery
Use in non-
coperative patients
Possible Not possible
Poor health patient Not safe Safer
Care for vital
functions
Essential Not needed

5. Historical perspectives
 First LA used was Cocaine
 1860, Albert Niemann isolated the active
principle, cocaine from Erythroxylon coca
 Karl Koller introduced it in clinical practice

6. Chemical Classification
Ester Linked
Procaine
Tetracaine
Benzocaine
Cocaine
Ester Linked
Procaine
Tetracaine
Benzocaine
Cocaine
Amide Linked
Lidocaine (Xylocaine)
Mepivacaine
Bupivacaine
Etidocaine
Ropivacaine
Amide Linked
Lidocaine (Xylocaine)
Mepivacaine
Bupivacaine
Etidocaine
Ropivacaine
LA structure

8. Q.Which of the following local anesthetics is not an amide?
A. Lidocaine
B. Bupivacaine
C. Procaine
D. Ropivacaine

9. Name some others drugs possessing significant
LA property but are not used as LA agent.

10.  Non irritant
 Negligible local tissue damage
 Minimal systemic toxicity
 Rapid onset of action
 Prolong action
 No after effects
Properties of ideal LA agent

11. Mechanism of action
 Blocks the voltage gated Na Channel
 Block the nerve conduction and propagation

12. Resting stage
Active stage
Inactive stage
Na +
Na +
Na +

13. Resting stage
Active stage
Inactive stage
Na +
Na +
Na +
BH+
B + H+
B + H+
 BH+

14. 1.Sensory > Motor
Pain ,Temp,Touch,Deep pressure, Motor function
2.Myelinated >Non myelinated
3. Size of fiber
Small fibres >large fibres
4. Autonomic fibres> somatic fibres
5.Tongue
Bitter >Sweet>Sour> Salt
Differential sensitivity of nerve fibers

15. Factors influencing LA action
Lipid solubility
Influence of pH
Vasoconstrictors
Inflammation

16. CNS
 Stimulation- followed by depression
 Respiratory depression
CVS
 Cardiac depressant
 Reduced excitability, conduction rate , ↓force of Contraction
 Quinidine like anti-arrythmic action
 Bupivacaine –Cardio toxic
Systemic effects

17. Smooth Muscle
 Reduced contraction of bowel
 Relaxation of vascular and bronchial smooth muscle
Neuromuscular Junction
 Block release of Ach
 Blockade of NMJ

18. Ester type LA
 Hydrolysis by cholinesterase in plasma
 Short acting and low systemic toxicity
Pharmacokinetics
Amide type LA
 Bound to alpha1 acid glycoprotein
 Hydrolyzed by liver microsomal enzymes (P450)
 Longer acting & more systemic toxicity

19. CNS
Low dose
Numbness of tongue, metallic taste
Restlessness, visual disturbances
High dose
Nystagmus,confusion,convulsion
Adverse effects
CVS
Arrhythmia
Hypotension
Bradycardia
Cardiovascular collapse
Methemoglobinemia Hypersensitivity

20. Q. Indicate the function, which the last to be blocked by Local
anesthetic?
A. Pain
B. Temperature
C. Motor function
D. Touch, pressure

21. Q.Which of the following statements is not correct for local
anesthetics?
A. In a tissue they exist either as an uncharged base or as a
cation
B. A charged cationic form penetrates biologic membranes
more readily than an uncharged form
C. Local anesthetics are much less effective in inflamed tissues
D. Low ph in inflamed tissues decreases the dissociation of
nonionized molecules

22. Cocaine
 Natural alkaloid from Erythroxylon coca
 Surface anesthesia
 CNS stimulant, Marked effect on mood and behavior
 Stimulation of VC,VMC, VC and TRC
 Sympathomimetic action
 Initially euphoria followed by dysphoria (DA reuptake)
 Not used presently
 Only indication- Ocular anesthesia

23.  Most widely used LA
 Effective by all routes
 Faster onset ,more intense, longer lasting than procaine
A/E
 Drowsiness, mental clouding
 Altered taste and tinnitus
 Muscle twitching, convulsion ,arrhythmia
Lidocaine (Xylocaine)

24. Uses
For all purposes where LA is required
 Cardiac arrythmia,Resistant status epilepticus
 Available as Injections, topical solution, jelly and ointment

25.  First synthetic LA
 Topically ineffective – disadvantage
 Not use due to low potency ,delayed onset & short duration
 Can be used for infiltration anesthesia and nerve block
 Systemic toxicity negligible because rapidly destroyed in
plasma
 Antagonize action of sulfonamide
Procaine

26.  Pharmacological effect similar to lignocaine
 Little vasodilation
 Suitable for IV regional block
 Cause methemoglobinemia
Prilocaine

27.  Long acting, potent amide
 Used for infiltration, spinal, nerve block and epidural
 Analgesia without significant motor blockade
 Popular drug for analgesia during labor
 High lipid solubility, high distribution in tissues and less in
blood
 More cardio toxic than other LA (prolong QT interval)
 Not given IV
 Available as 0.25%, 0.5% inj.
Bupivacaine

28. Clinical Use of Local anesthesia
 Topical anesthesia
 Infiltration anesthesia
 Never block
 Epidural block
 Spinal block
 IV regional block

29. EMLA (Eutectic mixture of local anesthetics)
Eutectic = Two solid substances mixed together in equal
quantities by weight form a eutectic mixture
Melting point of the mixture is lower than the melting point of
the individual components.
It can penetrates intact skin
Uses- Venupuncture,Skin grafting
EMLA = Lidocaine (2.5%) and Prilocaine (2.5%)

30. Site of application Formulations
Intact skin
Abraded skin
EMLA
Tetracaine 1 % cream/ointment
Ocular-tonometry Tetracaine drops/benoxinate
Nose/ear—polyp Lignocaine 2-4-tetracaine
Sore throat/Stomatitis Benzocaine Spray
Intubation/endoscopy Lignocaine 2-4-tetracaine
Oesophagitis,Gastritis Oxethazine with antacids
Urethral dilatation and catheterization Lignocaine gelly 2%
Proctoscopy,Anal fissure Lignocaine 4% ointment,suppository
Surface anesthesia and agents UsedSurface anesthesia and agents Used

31. Q.A 45-year-old male with alcoholic cirrhosis is seen in the ED
Because of a laceration of the scalp. Of the following local
anesthetics, which would potentially be toxic?
A .Lidocaine
B. Benzocaine
C. Procaine
D. Tetracaine

32. Q.Which of the following local anesthetics is more likely to cause
allergic reactions?
A. Lidocaine
B. Bupivacaine
C. Procaine
D. Ropivacaine

33. Summary

34. Thank You