Local anesthetics are drugs that cause reversible loss of sensation, especially pain, in a localized area of the body without damaging neurons. They work by blocking the generation and conduction of nerve impulses at the site of action, which is the axonal membrane. The order of block is pain, temperature, touch, pressure, and then motor function. Common local anesthetics include lidocaine, bupivacaine, tetracaine, and prilocaine. They provide analgesia for minor procedures but can also be used for major surgery via regional techniques like epidurals.

2. These are the drugs which upon topical application or local
injection causes reversible loss of sensory perception,
specially pain in a restricted part of body.
Block generation & conduction of nerve impulses at a
localized site without structural damage to neurons.
Loss of sensory as well as motor impulses
Site of action of LA-Axonal membrane
The order of block:-
Pain → Temp(cold before heat) → Touch → Pressure →
Skeletal muscle power

3. Properties of Ideal LA
Non-irritant/Negligible local irritation
Negligible local tissue damage
Minimal systemic toxicity
Rapid onset of action
Prolonged action
Water soluble
Sterilizable by heat
Without any after effect

4. Advantage & disadvantage of LA Over GA
Advantages of LA over GA
 Consciousness is present
 Only specific localized area is affected
 No physiological disturbances as observed with GA
 Monitoring of vital functions is usually not required
 Response to pain & stress can be modified selectively
 Safe in pt. with poor general condition
Disadvantages of LA as compared to GA
 Cannt be used in uncooperative pt.
 Usually suitable for minor surgery but can be used in major surgery by
spinal & epidural anaesthesia
 Can produce serious side effect

5. LA VS GA
Actions GA LA
Site of Action CNS Peripheral tissue
Area Whole body Restricted area
Consciousness Lost Unaltered
Preferential use Major surgery Minor surgery
Use in non-cooperative
pt.
Possible Not Possible
Poor health pt. Risky Safer
Care for vital functions Essential Not needed

6. Basic structure of LA
Most are weak bases
They consist of three parts-
I. hydrophilic amino (tertiary/secondary) group
II. lipophilic aromatic group
III. intermediate ester or amide linkage.
Lipophilic Hydrophilic
Lipophilic group
 responsible for LA action
 ↑duration & potency
 ↑receptor affinity-receptor
site lipophilic
 ↓metabolism by plasma
esterase & liver enzyme
 More lipophilic-more
toxicity
 Molecular size-affect the
rate of dissociation from
receptor
 Small molecule –rapidly dissociate from tissue

7. History:-
• 1860-first LA- cocaine was accidentally discovered by
Albert Niemann-caused numbing of the tongue
• Cocaine is a Alkaloid(ester of benzoic acid) has natural
nitrogen bases found in the coca leaves
• 1884-Carl koller- introduced in clinical Practice –topical
anesthetic agents for ocular surgery
• High addition liability
• Prototype drug-Lignocaine

8. Classification-of LA according to Clinical use:
LA
Injectable Surface
Short acting with
low potency
Long acting with
high potency
Intermediate potency
& duration
Procaine
chloroprocaine
Tetracaine
Bupivacaine
Ropivacaine
Dibucaine
Lidocaine(Lignocaine)
Prilocaine
Cocaine
Lidocaine
Tetracaine
Proparacaine
Benzocaine
Butylaminobenzoate
oxethazaine
Classification according to structure:-
 Esters:-Cocaine, procaine, chloroprocaine, benzocaine, tetracaine,
 Amides:-
Lignocaine,mepivacaine,bupivacaine,prilocaine,articaine,ropivacaine

9. Mechanism of action:-

10. • Blocked is frequency dependent
• Action of local anesthetic is pH dependent
• ↑penetrability of LA →at alkaline pH
• ↓↓ penetrability of LA →at Acidic pH e.g.-infected/inflamed
tissue
• LAs are less effective in inflamed and infected areas-because
inflamed/infected tissue-pH is acidic-less penetration
• LAs block small fibers first followed by larger fibers
• Myelinated fibers are blocked earlier

11. Factors affecting local anesthetic action:-
LAs are Weak Bases Inflamed & Infected Areas
pH
Unionized at Alkaline pH Ionized at Acidic pH
Increased Penetrability Poor Penetration of LAs
Through Membranes through Cell Membranes
Good Local Anesthesia Therefore LAs are Less Effective in these Areas
 pH:-

12.  pKa:-
• The pKa is the pH at which the drug is 50% ionized and 50%
unionized. The onset of action depends on pKa
At higher pKa
↑Ionized fraction
Slow onset of action
( Procaine)
At lower pKa
↑↑unionized fraction
Rapid onset
(Lignocaine)
 Except-Chloroprocaine having rapid onset despite high pKa

13.  Degree of plasma protein binding
Duration of action depends upon the Protein binding
Procaine:- poorly bound to PP and has short duration of
action
Bupivacaine: Highly bound to PP and has a longer
duration of action
 Rate of diffusion from the site of administration:-
 Higher the concentration - rapid onset of action
 Lipid solubility:-
Higher the lipid solubility more is the Potency of the drug
E.g.- Lignocaine is more potent than Procaine

14.  Nerve fiber:-
 Size & Degree of myelination- small-diameter fibers are
blocked earlier than the larger fibers
Myelinated fibers – at least 2-3 nodes of Ranvier must be
blocked by LA to block the conduction of impulses
Sensory fibers have a higher firing rate and long AP duration
than motor fibers. Therefore sensory fibers are blocked
earlier

15. Presence of vasoconstrictor:- (Cocaine itself vasoconstrictor)
Advantages:-
Slow absorption from the local site, which results in prolonged
duration of action of local anaesthesia.
Decreased bleeding in the surgical field.
Slow absorption of LA reduces its systemic toxicity
Disadvantage:-
Intense vasospasm and ischemia in tissues with end arteries may cause
gangrene of the part (e.g. Fingers, toes, penis, ear lobule, tip of the
nose, etc.). Hence, use of vasoconstrictors is contraindicated in these
sites
Absorption of adrenaline can cause systemic toxicity—tachycardia,
palpitation, rise of BP and precipitation of angina or cardiac
arrhythmias.

16. May delay wound healing ↓↓Blood flow to the affected
area.
Commonly use agents are-LA(Lignocaine)+adrenaline,
phenylephrine
Combination Should be avoided-
cardiovascular disease-like CCF, Hypertension,
Arrhythmias, hyperthyroidism, ischaemic heart disease
• Pt. on halothane & potassium sparing diuretics, MAO-
inhibitors,tricyclic antidepressants
• Preferred drug- Felypressin (vasopressin analogue)-safe
contraindicated-pregnancy- uterine stimulant

17. Pharmacological actions:-
PNS:-Autonomic fibers blocked earlier than somatic
Order of block in somatic afferents are : pain – temp – touch –
pressure and motor fibers
CNS:- Initial CNS stimulation later depression action
• as they cross BBB-excitation, tremor, restlessness, convulsion,
euphoria
• Higher dose-Respiratory depressant, coma, death
CVS:-
On heart:- LAs are cardiac depressants
↓HR, ↓Excitability, ↓Contractility,
↓CO, ↓Conductivity, ↑ERP
• Lignocaine is used as an antiarrhythmic(class-I)
• At higher conc.-LAs can induce arrhythmias
• Bupivacaine is more cardiotoxic

18. Smooth muscle:- ↓contraction of bowel &
relaxation of vascular & bronchial smooth muscles
Pharmacokinetics:-
• (Because LAs act near their site of administration
pharmacokinetic characteristics are not important
determinants of their efficacy)
• LAs (procaine, lignocaine, etc.) are not effective orally
because of high first-pass metabolism
• Ester-linked LAs - rapidly metabolized by plasma
cholinesterase Amide-linked -metabolized mainly in liver
• In liver diseases, the metabolism of lignocaine may be
impaired; hence dose must be reduced accordingly

19. Adverse effects:-
1. CNS- restlessness, tremor, headache, drowsiness, confusion
and convulsions followed by respiratory
depression, coma and death.
2. CVS:- Bradycardia, hypotension, cardiac arrhythmias,
rarely cardiovascular collapse and death.
Bupivacaine is highly cardiotoxic.
3. Allergic reactions:- These are skin rashes, itching,
erythema urticaria, wheezing, bronchospasm and rarely
anaphylactic reaction. The incidence of allergic reactions is
more with ester-linked LAs than with amide-linked LAs.
4. Methemoglobinemia-prilocaine, benzocaine.
5. Methylparaben, a preservative in LA solutions, may cause
allergic reactions.

20. -:Cocaine:-
• Source: Erythroxylon Coca leaves-south American plant
• First used in ocular anesthesia in 1884.
• LA action+ Vasoconstriction (inhibition of reuptake of NA)
• It produces CNS stimulation with marked effect on mood &
behavior, sense of wellbeing, delay fatigue.
• Addiction liability-due to euphoria(Drug of Abuse)
• Rarely used in ocular anesthesia-due to mydriatics
• SE:-↑BP, tachycardia, nausea, vomiting, pyrexia(↑heat
production)
Treatment of abuse:- modafinil-↓euphoria

21. Lignocaine(Lidocaine)
oPrototype for Amide linked LA
oIt is also popular Class-I anti-arrythmic agent
oBroad spectrum LA- due to
 Rapid onset of Action
Good tissue penetrability
Without Vasoconstriction action-cardiovascular dependent effect
Addition of Vasoconstrictor-↑duration &↓systemic toxicity
Available as a patch-to control pain in neuralgia
oUSES:-
o Cardiac arrhythmias
o Resistance case of status epilepticus
oPharnynx, larynx,trachea -intubation,tonsil surgery,endoscopy
o Piles,fissures surgery-suppository,ointment
⁕Not to be used-pt. With a history of malignant hyperthermia

22. Eutectic Mixture of Local Anaesthesia
(EMLA)
• Mixture of Lignocaine 2.5% + Prilocaine 2.5% (cream)
• Melting point of mixture is less than that of either compound
alone
• Room temp-become a oil mixture- Can penetrate intact skin
up to 5 mm depth
• Uses:- (1hr before procedure)
- Venipuncture-dermal anesthesia
- Skin graft procedures
Caution:-EMLA must not be applied to the Mucous
membrane
• Contraindication- Methemoglobinemia

23. Tetracaine:-
• long duration but slow onset of action-used as spinal anesthesia
• Slow metabolism-causes toxicity
Bupivacaine:-
• Potent & long acting, amide LA used for infiltration, nerve block,
epidural & spinal anesthesia of long duration.
• It also provides good analgesia.
• It produces more sensory than motor blockade; hence it is very popular
for obstetric analgesia
• Cardiotoxic-precipitate ventricular arrhythmias.
Ropivacaine:-
• It is less potent and less cardiotoxic than bupivacaine. Its duration of
action is similar to bupivacaine.
• It is used for both epidural and regional anesthesia

24. Prilocaine
• It is an amide type of LA.
• It has intermediate onset and duration of action.
• It has poor vasodilatory effect
• It is mainly used for infiltration and i.v. regional
anaesthesia.
Dibucaine:-
• Very potent, Very toxic & Longest acting
• Uses:-
- for spinal anethesia
- for topical (surface anaesthetic) on mucous membrane
& skin

25. • Oxethazaine:-
• Topical anesthetic
- to anaesthetize gastric mucosa
- produces symptomatic relief in gastritis
- available with antacids
Benzocaine Butylaminobenzoate:-
• Poorly water soluble
• Poorly absorbed on topical administration
• Uses:-
- as lozenges in sore throat
- as powder/ointment on wounds/ulcers
- as suppository for anorectal lesions

26. Techniques of Local Anaesthesia

27. • Surface anaesthesia
• Infiltration anaesthesia
• Conduction block-A. Field block
B. Nerve Block
 Spinal anaesthesia
 Epidural anaesthesia
 Intravenous regional anaesthesia

28. LA techniques Drugs Therapeutic
application
Surface anaesthesia
(topical)
• Lignocaine (2–10%)
• Tetracaine (2%)
• Benzocaine
To anaesthetize mucous
membrane of oral cavity
before injecting local
anaesthetic, subgingival
and periodontal scaling
Infiltration
anaesthesia
• Lignocaine (0.5–1%)
• Procaine (0.5–1%)
• Bupivacaine (0.125–0.25%)
• Ropivacaine
Abscess drainage
• Excision of small
swellings
• Suturing of cut wounds
• Before root canal
treatment
Field block(conduction block) • Lignocaine (0.5–1%)
• Bupivacaine (0.125–0.25%)
Maxillary injections above the
apex of tooth to be
treated

29. LA techniques Drugs Therapeutic
application
Nerve Block (conduction
block)
Most of the anaesthetics Maxillary nerve block •
Anterior superior alveolar
nerve block for
management of anterior
teeth in one quadrant
Spinal anaesthesia Lignocaine(1.5-5%)
Tetracaine (0.25%-0.5%)
Bupivacaine (0.5%)
Surgery of lower limbs
Lower abdomen, perineum
etc. caesarean section
Epidural anaesthesia Lignocaine(2%)
Bupivacaine(0.5%)
Ropivacaine
Obstetric analgesia
Intravenous regional
anaesthesia
Lignocaine (0.5%)
Prilocaine (0.5%)
For upper & lower limb
surgery

30. Surface anaesthesia/topical anaesthesia
• Sensory nerve endings are blocked
• Only superficial layer is anaesthetized-topical application
• No action-submucosal structure-pain relief don’t occur
• Available formulation-
form,cream,ointment,spray,EMLA
• Lignocaine-commonly use (EMLA) for intact skin
• Peak anesthetic effect occurs in 2-5 min & lasts for 30-45
min

31. • Used:-
on mucous membranes & abraded skin - nose, mouth, eyes,
throat, URT, urethra, ulcers, burns, fissures, etc
 can also be used- i.v. cannulation, during endoscopies,
Tonometry
E.g.- lignocaine, tetracaine, benzocaine, cocaine, dibucaine
Systemic toxicity-due to rapid absorption
Drugs use-Lignocaine (2–10%) Tetracaine (2%),
Benzocaine
LA Cannt be used due to poor penetration- Bupivacaine,
Ropivacaine, Mepivacaine, Procaine

32. Spinal Anaesthesia
• It is one of the most popular forms of anaesthesia.
• LA injected - subarachnoid space (space between pia & arachnoid
matter also called as intrathecal space ) to anaesthetize spinal roots
• Site:-Spinal anaesthetic is injected into the space between L2–L3 and
L3–L4 below the lower end of the spinal cord
The level of anaesthesia is influenced by:
• Site of injection
• Amount of fluid injected
• Force of injection
• Position of the pt.- pt is kept in particular position depends on the area
to be anaesthetize -lying prone/lateral or tilted with head down position
LA Used for spinal anaesthesia-
• Lignocaine, Bupivacaine
• Addition of Adrenaline-↑duration/intensity of block

33. • Uses:-
• Lower limb surgery-below the level of umbilicus
• Caesarean section
• Obstetric procedures
• Prostatectomy
• Appendicectomy
• Surgeries on perineum, etc.
Advantage:-
No loss of consciousness
Good muscle relaxation
Good analgesia
Pt.with cadiac,pulmonary,renal disease-better tolerated than
GA

34. SE:-
• Hypotension:- Sympathetic blockade (Spinal nerve roots)
Vasodilatation (mainly veins)
Pooling of blood into the capacitance vessels
↓↓Venous return-↓↓COP
Hypotension
 Raise the legs (To ↑ venous return )
 O2 administration
 Intravenous fluids
 Vasopressors:
- Ephedrine 5-10 mg i.v. DOC
-Phenylephrine i.v / i.v. infusion

35. Headache- due to leakage of CSF.(less in elderly)
Start-begins within few hr.may last a week
Rx-prevented by using need of minima possible diameter
(small bore) (25G)/pencil-point needle
Respiratory paralysis- (rare)
Reason-due to the paralysis of intercostal muscles as a
result of hypotension.
Infection(Sepsis/Meningitis):-
Rx- by strict aseptic condition
Cauda equina syndrome- loss of control over sphincters
of bladder and bowel.

37. Infiltration anaesthesia
• LA-Injected-directly into the skin(the tissue to be operated)
• LA used:-lignocaine, procaine, bupivacaine
Uses:- (Minor surgeries) e.g.-
Incision, excision of small swelling
drainage of abscess,
suturing of cut wounds
Before RCT
Gingivectomy
• Addition of adrenaline-prolong the duration
Disadvantage:-
large amount of drug needed
Suitable for only small areas
Contraindicated- clotting disorder

38. Conduction block
1.Field Block anesthesia:-
Achieved by injecting a LA via SC route
Used:-
minor procedure of scalp, Anterior abdominal wall, upper and lower
extremities
Maxillary injections above the apex of tooth to be treated
Drug:- Lignocaine (0.5–1%) Bupivacaine (0.125–0.25%)
Advantages:-
Small dose-produce-larger area of anaesthesia
Prolong duration of action

39. Nerve Block
• LA injected around the nerve trunk → area distal to injection
is anaesthetized & paralyzed
• It produces larger of anesthesia than field block
• LA requirement-less than Filed block & infiltration
• USE:-Maxillary nerve block • Anterior superior alveolar
nerve block for management of anterior teeth in one quadrant
Site:-
Brachial plexus block - upper limb surgeries
Cervical plexus block- surgery of neck
Intercostal nerve block – ant. Abdominal wall surgery
Sciatic & femoral nerve block-surgery distal to knee
Almost all anesthetics can be used for this technique

40. Epidural anesthesia
• LA injected - epidural space(b/w duramater & bone), where
it acts on spinal nerve roots
• LA use:- Lignocaine, bupivacaine, Ropivacaine
Use:-(All surgeries which can be perform under spinal
Anaesthesia)
painless labor
Cancer pain
to control post operative pain
to control chronic pain
Advantage over Spinal anaesthesia:-
Slow onset-suitable for the procedure of long duration

41. Intravenous regional anaesthesia
(Bier’s block)
LA is injected into the vein of the limb whose blood
flow is occluded by a tourniquet
Mainly used to anaesthetize upper limb
Lignocaine and prilocaine

42. Drug interactions:-
• Lignocaine × propranolol-
(propranolol by reducing hepatic Blood flow-↓clearance of
lignocaine-leading to toxicity
• procaine × sulfonamides-
-(Procaine hydrolyzed to PABA-reduce the effect of
sulfonamides)