2. Definition
• produce loss of sensation to pain in a specific
area of the body without the loss of
consciousness.
• produce loss of feeling to pain in a specific
area of the body without the loss of
consciousness
3. Some Clinical Examples
• Topically: Nasal mucosa and wound
margins
• Infiltration: Vicinity of peripheral nerve
endings and major nerve trunks
• Epidural or Subarachnoid spaces:
surrounding spinal nerves
• Regional anesthesia: Intravenous
injection in arm or leg (Bier block)
4. Local Vs General Anaesthesia
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 Risky Safer
Care for vital functions Essential Not needed
5. History:
• In Western Europe between 1750 to 1850
• Chemists and physicians collected sample of coca
leaves for experiments
• Isolated active principle of coca leaf, synthesized to a
drug for patients to feel more relief of pain when taking
surgeries
• In 1860, German chemist Albert Niemann successfully
isolate the active principle of coca leaf; he named it
cocaine
• Cocaine, an ester of benzoic acid and methylecgonine
8. – Ester-linked
• Short acting
• Metabolized in the plasma and tissue fluids
• Excreted in urine
– Amide-linked
• Longer acting
• Metabolized by liver enzymes
• Excreted in urine
REMEMBER: All are weak Bases!
9. ANOTHER
(Classification)
• Injectable anaesthetic:
– Low potency, short duration – Procaine and Chlorprocaine
– Intermediate potency – Lidocaine (Lignocaine) and Prilocaine
– High potency and long duration – Tetracaine, Bupivacaine,
Ropivacaine, Etidocaine, Mepivacaine and Dibucaine
(Cinchocaine)
• Surface anaesthetic:
– Soluble – Cocaine, Lidocaine, Tetracaine and Benoxinate
– Insoluble – Benzocaine, Butylaminobenzoate and Oxethazine
• Miscellaneous drugs:
– Clove oil, phenol, chlorpromazine and diphenhydramine etc.
10. Mechanism
• The mechanism of local anesthetics connects with the ion
channels, nerve, and depolarization.
• Local anesthetics block the conduction in peripheral nerves
that inhibited the nerve to excited and created anesthesia.
• The anesthetic is a reversible reaction. It binds and
activates the sodium channels.
• The sodium influx through these channels and depolarizes
the nerve cell membranes. It also created high impulses
along the way.
• As a result, the nerve loses depolarization and the capacity
to create the impulse, the patient loses sensation in the
area supplied by the nerve
11.
12.
13.
14. Procaine (Novocaine)
– Topically ineffective - disadvantage
– Used for infiltration because of low potency and short
duration but most commonly used for spinal
anesthesia
– Short local duration ......produces significant
vasodilation. Adrenaline used to prolong effect
– Systemic toxicity negligible because rapidly destroyed
in plasma
– Procaine penicillin
15.
16.
17. LIDOCAINE (Xylocaine) Most widely used and popular LA
– Effective by all routes – topical, infiltration, spinal etc.
– Faster onset (3 Vs 15 min), more intense, longer lasting (30 – 60
min.), than procaine
– Addition of Adr in 1:200,000 prolongs the action for 2 Hrs
– More potent than procaine but about equal toxicity
– Quicker CNS effects than others (drowsiness, mental clouding,
altered taste and tinnitus)
– Overdose (muscle twitching, cardiac arrhythmia, fall in BP, coma
and respiratory arrest)
– Antiarrhythmic
– Available as Injections, topical solution, jelly and ointment etc.
