Local anaesthetic, pharmacology, classification

1. Presented by
Sandeep AC
M.Pharm 1st SEM
Dept of pharmacology

2.  Local anesthetics are drugs which upon topical
application or local injection cause reversible loss of
sensory perception, especially of pain in a localized area
of the body
 Is the loss of sensation in a circumscribed area of the
body caused by a depression of excitation in nerve
endings or an inhibition of the conduction process in
peripheral nerves

3.  The clinically useful LAs are weak bases with
amphiphilic property. A hydrophilic secondary or
tertiary amine on one side and a lipophilic aromatic
residue on the other are joined by an alkyl chain
through an ester or amide linkage.
 Ester linked LAs: Cocaine, procaine, chloroprocaine,
tetracaine, benzocaine.
 Amide linked LAs: Lidocaine, bupivacaine, dibucaine,
prilocaine, ropivacaine.

6. MECHANISM OF ACTION

7. The LAs interact with a receptor situated
within the voltage sensitive Na+ channel and
raise the threshold of channel opening: Na+
permeability fails to increase in response to an
impulse or stimulus. Impulse conduction is
interrupted when the Na+ channels over a
critical length of the fibre are blocked.

8. 1.LOCAL ACTIONS
 block sensory nerve endings, nerve trunks,
neuromuscular junction, ganglionic synapse and
receptors
SYSTEMIC ACTIONS
1.Blood vessels
 LAs tend to produce fall in BP. due to sympathetic
blockade,
 Bupivacaine is more vasodilatory than lidocaine.

9. 3.C.N.S
 All LAs are capable of producing a sequence of
stimulation followed by depression.
 Cocaine is a powerful CNS stimulant causing in
sequence
 euphoria—excitement—mental confusion—
restlessness—tremor and twitching of muscles—
convulsions—unconsciousness—respiratory
depression—death, in a dose-dependent manner.

10.  they decrease automaticity, excitability, contractility,
conductivity
 LAs are cardiac depressants, but no significant effects
are observed at conventional doses.
 amide derivative procainamide is a class IA
antiarrhythmic
 Bupivacaine is relatively more cardiotoxic and has
produced ventricular tachycardia
 Lidocaine has little effect on contractility and
conductivity;

11.  Procaine is only 6% protein bound and has a very short
duration of action, where as bupivacaine is 95% protein
bound. bupivacaine have a longer duration of action
 Soluble surface anaesthetics (lidocaine, tetracaine) are rapidly
absorbed from mucous membranes
 The absorbed LA being lipophilic is widely distributed
 Esters (except cocaine) are broken down rapidly by plasma
esterases to inactive compounds and consequently have a
short half life. Cocaine is hydrolysed in the liver. Ester
metabolite excretion is renal.
 Amides are metabolised hepatically by amidases. This is a
slower process, hence their half-life is longer

12.  CNS effects are light-headedness, dizziness, auditory
and visual disturbances, mental confusion,
disorientation, shivering, twitching, involuntary
movements
 Cardiovascular System: bradycardia, heart block,
vasodilation
 Hypersensitivity reactions like rashes, angio- edema,
dermatitis

13. Infiltration anaesthesia - is often used for minor surgical and
dental procedures. Nerve block anesthesia is used for
surgical, dental, and diagnostic procedures and for pain
management.
Surface anasthesia local anesthetic that is used to numb
the surface of a body part. They can be used to numb any
area of the skin as well as the front of the eyeball, the inside
of the nose, ear or throat, the anus and the genital area
Conduction block -LA is injected around nerve trunks so that
the area distal to injection is anaesthetised and paralysed.

14. epidural anesthesia is often used during labor and delivery, and
surgery in the pelvis and legs

16.  The pharmacological basic of therapeutics by
Goodman and gilman of 12th edition 565-587
 Essential of medical pharmacology by
K.D.Tripati of 7th edition 360-376

17. Thank you