Drugs that cause reversible loss of sensory
perception specially of pain in a restricted
area of the body, when applied topically or
LA if applied to a mixed nerve—sensory and
motor impulses are interrupted—resulting in
muscular paralysis and loss of autonomic
Reversibly block the impulse conduction
Transient loss of sensation
Local anaesthesia blockade
C,B > Aδ > Aα,ß,γ
E S T E R S
Short duration of action
Less intense anesthesia
Higher risk of
Hydrolyzed by Plasma
Cholinesterase in blood.
Rarely used for Infiltration
anesthesia But useful for
topical anesthesia on
A M I D E S
Produce more intense and
longer lasting anesthesia
Bind to alpha1 acid glyco-
protein in plasma
Rarely cause hypersensitivity
reactions- no cross
reactivity with ESTER L A s
Not hydrolyzed by Plasma
Cholinesterase, but in liver
Vasoconstrictor is a substance used to keep the
anesthetic solution in place at a longer period and
prolongs the action of the drug
Vasoconstrictor delays the absorption which slows
down the absorption into the bloodstream
Vasoconstrictor used ---the natural hormone called
Blockage of membrane depolarisation in all excitable
tissues, usually intended on peripheral nerve
They prevent the
Initiation and propa-
Gation of the nerve
Impulse by reducing
the passage of Na
Effects of LA: injection as acid (hydrochloric salt)=
ionized form at physiological pH dissociation to
free base (lipid soluble) passage through cell
membrane to interior of axon re-ionisation
enter and blockage of Na+-channel and thereby
preventing influx of Na+ no generation of AP
They block nerve conduction by reducing the
permeability of Na ions during depolarisation
Should not be coadministered for nerve block in areas such
as fingers and toes that are supplied with end-arteries
because it may cause ischemia or necrosis
It should be used cautiously in patients in labour and in
patients with thyrotoxicosis or cardiovascular disease.
Usually at range 7.6 – 8.9
Decrease in pH shifts equilibrium toward the ionized
form, delaying the onset action.
Lower pH, solution more acidic, gives slower onset
Presence of Pus and inflammation will retard the
action of LA. ( probably low acidic pH)
Most widely used Amide linked LA and most
Has variety of applications like Local, nerve block,
spinal, epidural, IVRA.
When used locally action starts within 3 mts and
Overdose causes muscle twitchings, convulsions,
cardiac arrhythmias, fall in BP, coma, respiratory
Most popular ant arrhythmic drug
• Standard agent for infiltrations, regional blocks or
• Short onset time, intermediate duration of action
• Class Ib antiarrhythmic properties
• Medium toxicity
• Maximal recommended dose: 3 mg/kg, 6 mg/kg with
A potent long acting ---Amide linked LA available in
India, most widely used allover.
Not used for IVRA but all others like local, spinal
Action lasts for 2 to 3 hours. Strength for epidural is
0.25 to 0.5 % solution.
Has high lipid solubility, distributes more in tissues
than in blood
It is similar to Bupivacaine
One of the metabolites are toxic and can cause
Used for Nerve Blocks and IVRA.
Causes more sensory block, than motor block the
advantage taken in during Caesarean Section.
Bupivacaine is more prone to prolong QTc interval
and induce ventricular tachycardia or Cardiac
depression----( Membrane Stabilization action ) (
toxic doses and accidental entry into vessel)-should
not be used for IVRA.
Longest acting LA available in India now.
1. Surface anesthesia
2. Infiltration anesthesia
3. Conduction block a. Field block b. Nerve Block
4. Spinal anesthesia
5. Epidural anesthesia
6. I V R A (Bier’s Block)
Amethocaine ---eye, throat, urethra, rectum and
Benzocaine and Lidocaine hydrochloride—same ---
except for eye.
Procaine is unsuitable as a surface ana. Because of
its poor penetrating power
Lignocaine --4 % topical solution, 2 % Jelly
2 % vials for injections
Eutectic : Lowering of melting point of two solids
when they are mixed.
combination of Lidocaine and Prilocaine.
For Pediatric purpose. It can penetrate intact skin.
I v .cannula inserting.
Split skin graft harvesting
Other superficial procedures.
Mech. of action : Nerve endings as exposed to the
drug there by action.
Procaine, Lignocaine 2 % are used either with or
without Adrenaline 1 : 2,00,000
C/I : blocking where end arteries are involved either
for Penis, or for Digits, C A D patients.
Drug is injected close to the nerve or big nerve
trunks eg. Brachial Block, Sciatic, Femoral Nerve,
Radial, Ulnar Nerves.
LA is injected into the subarachnoid space.
Injection is made heavy by adding dextrose or light
by adding saline.
When the anesthetic in injected outside the dura,
the technique is known as Epidural anesthesia.
Lignocaine, Bupivacaine the two agents most
commonly used regularly in anesthesia practice.
Intravenous regional anesthesia
Agent of choice------ Lignocaine (Xylocaine )
20 to 40 ml of 0.5 % Lidocaine is used
Used for only for Upper Limb orthopedic surgeries
and others on Up. Limb.
We have seen all Local actions of LA s
Systemic action when given IV : Bupivacaine is
relatively more cardiotoxic , produces ventricular
tachycardia or fibrillation.
Lidocaine has little effect on contractility and
conductivity, used as antiarrhythmic.
The prominent cardiac action of Xylocaine is
suppression of automaticity in ectopic foci.
Depression of function of CNS and CVS when high
plasma concentrations are reached
CNS toxicity : usually before cardiovacular effects
First signs of excitation due to initial blockade of
mild: circumoral tingling, metallic taste, tinnitus,
visual disturbance, slurred speech
moderate: altered consicous state, convulsions
Later sings of generalized CNS depression with
potentially fatal toxicity: coma,respiratory arrest
1.Bradycardia, 2.Hypotension 3.Headache
4.Cauda Equina syndrome 5.Septic meningitis
EPIDURAL ANESTHESIA :
Here the drug is injected outside the dura. Drug
spread is restricted to a specific region causes fewer
Allergic reactions: common with ESTERS like
Procaine, caused by para-aminobenzoic acid (also
found to cause arachnoiditis), less common with
AMIDES, then mostly through preservatives
Drug interactions: i.e. Anticholinesterases, other
competing drugs hydrolyzed by Plasma CE
Attention with heavy sedation with anticonvulsants:
may mask early signs of toxicity
Methaemoglobinaemia: after large doses Prilocaine