LOCAL ANAESTHESIA

1. Local anaesthesia
KHYATI PHUYAL
MBBS STUDENT

2. • They are the drugs that reversivibly inhibit the
sensory,motor or autonomic nerve pathway
after when injected or applied to the tissue

3. classification
ESTER AMIDE
cocaine lignocaine
procaine bupivacaine
chloroprocaine ropivacaine
tetracaine prilocaine
benzocaine mepivacaine

4. Duration of action
1.Low potency short duration(30min)
procaine
chloroprocaine
2.Intermediate potency and duration(1-1.5 hrs)
Lidocaine
prilocaine
3.High potency long duration
Tetracaine
Bupivacaine
Dibucaine

5. • They are amphiphilic ,
• Hydrophilic amine on one side
• Lipophilic aromatic residue on other side

7. MOA
• It block the nerve conduction by decreasing
entry of sodium ion during of upstroke of
action potential
• It interact with the receptor with in the
sodium channel
• At physiological PH,LA molecule partly ionozed
• B___BH+
• The eqilibrium between these is depend on
pka of the LA

9. • In the base forms(B),it penetrate the axon
• The molecule which has lower pka which is in
the undissociated form in PH 7.4
• In the undissociated form it enters the axon
and rapid in action
• Higher pka are slower in action

10. • Local anesthetics have a greater affinity for
the channel in the open or inactivated state
than in the resting state
• Sensitivity is determined by diameter ,fiber
type,myelinationor non mylinated

12. • Automatic fiber are more susceptible
• In somatic
(pain>temperature>touch>pressure)
recovery in reserve

13. Pharmacokinetics
A.Absorption
- from mucous membrane easily absorbed
- intact skin require high concentration
-systemic absorption depend on blood
flow
which depends on

14. 1. Site of injection —
Th e rate of systemic absorption is related
to the vascularity of the site of injection:
intravenous (or intraarterial) > tracheal >
intercostal > paracervical > epidural > brachial
plexus > sciatic > subcutaneous.

15. 2.Presence of vasoconstrictor(adrenaline)
-prolongs the duration of action
-reduce the systemic toxicity
-provide a more bloodless field
3. Local anesthetic agent —More lipid-soluble
local anesthetics that are highly tissue bound
are also more slowly absorbed?

16. B.Distribution
-initial rapid ypteke in highly perfused organ
(brain,lung,liver,kidney)
- then to lesser perfused tissue

17. C. Biotransformation
1.Esters
metabolized by pseudocholinesterase
(plasma cholinesterase or butyrylcholinesterase)
Procaine and benzocaine are metabolized to
p -aminobenzoic acid (PABA), which has been
associated with rare anaphylactic reactions

18. 2.Amides
-metabolized (N-dealkylation and
hydroxylation) by microsomal P-450 enzymes in
the liver
-hepatic dysfunction increase the risk of
systemic toxicity
- prilocaine is metabolized to 0-toulidine
causes methaemoglobinaemia in dose
dependent manner

19. Pharmacodynamics
• Neurological
- inhibit the neuronal function temporarily
- cocaine is powerful CNS stimulation
- early neurological symptom include
circumoral numbness,abnormal sensationin
tongue, dizziness,blurred vision ,tinitus,
followed by drowsiness

20. • Respiratory
apnea
bronchail smooth muscle dilate
• cardiovascular
myocardial automaticity ,Myocardial
contractility and conduction velocity are also
depressed at higher concentrations
• immunological
hypersensitivity