Presentation on local anaesthetics - Chandragiri Siva sai Includes: Introduction, Classification, Mechanism of action, Duration of action, side effect and different phenomena of anesthetic agent.

1. PRESENTATION ON LOCAL
ANAESTHETICS
PRESENTED BY:-
CHANDRAGIRI. SIVA
SAI

2. WHAT ARE LOCAL ANAESTHETICS?
• LOCAL ANAESTHETICS produces short term effect
and reversible loss of sensation (analgesia) in a
specified region of the body without loss of
consciousness.
• Normally, the process is completely reversible.

3. HISTORY
In 1860, German chemist Albert Niemann successfully isolated the
active principle of coca leaf; he named it cocaine.
Cocaine is an ester of benzoic acid and methylecgonine.

5. CLASSIFICATION
• INJECTABLE ANAESTHETICS:-
• Low potency, short duration:- procaine and chlorprocaine
• Intermediate potency:- Lidocaine and prilocaine
• High potency and long duration:- Tetracaine, Bupivacaine, Ropivacaine,
Etidocaine, mepivacaine and Dibucaine

6. SURFACE ANAESTHETICS:-
Soluble- cocaine, lidocaine, tetracaine and benoxinate.
Insoluble- benzocaine, butyl aminobenzoate and oxethazine
MISCELLANEOUS DRUGS:-
clove oil,phenol,chlorpromazine and diphenhydramine etc.,

7. BASED ON THE STRUCTURE
• LOCAL ANESTHETICS – (ESTERS OR AMIDES )
•A lipophilic aromatic group
•To a hydrophilic, ionizable amine.
• Most are weak bases

9. CLASSIFICATION BASED ON THE
CHEMICAL STRUCTURE
ESTERLINKED:-
• Benzocaine
• Procaine
• Proparacaine
AMIDE LINKED:-
• Bupivacaine
• Levobupivacaine
• Lidocaine/lignocaine
• Mepivacaine

11. MECHANISM OF ACTION
• LOCAL ANESTHETICS Produce ANESTHESIA By inhibiting excitation of nerve endings or by
blocking conduction in peripheral nerves.
• This is achieved by anesthetics reversibly binding to and inactivating sodium channels.
• Local anesthetics cause a reversible inhibition of action potential conduction by binding to the sodium
channel and decreasing the nerve membrane permeability to sodium.
• The nonpolar, lipophilic form of the anesthetic molecule passes through the neuronal membrane and
switches to the polar, hydrophilic form in the cytoplasm of the neuron.
• This cationic form of the anesthetic binds to the cytoplasmic side of the sodium channel protein
and prolongs the inactivation state of the sodium channel. With sodium channels blocked, action
potentials cannot propagate along the neuronal fiber and sensory input is lost.

13. SEQUENCE OF CLINICAL ANESTHESIA
• SYMPATHETIC BLOCK (VASODILATATION)
• LOSS OF PAIN AND TEMPERATURE SENSATION
• LOSS OF PROPRIOCEPTION
• LOSS OF TOUCH AND PRESSURE SENSATION
• LOSS OF MOTOR FUNCTION

14. DURATION OF ACTION
• The duration of action of local anesthetics can be short, medium, or long.
• Because local anesthetics act directly at the site of administration.
• Their duration of action is determined primarily by the rate of diffusion and
absorption away from the site of administration.
• Diffusion and absorption, in turn, depend on the chemical properties of the
anesthetics and on such factors as local ph and blood flow.
• In some formulations, epinephrine is added to prolong a local anesthetic’s
duration of action by producing vasoconstriction and slowing its rate of
absorption.

15. ROUTE OF ADMINISTRATION
•LOCAL ANESTHETICS Are usually
administered parenterally but are sometimes applied
topically. The route of administration depends on
factors such as the site of anesthesia.
•Mainly the following routes

16. TYPES OF ROUTES TO
ADMINISTERED
• TOPICAL ANESTHESIA
• INFILTRATION ANESTHESIA
• IONTOPHORESIS
• SPINAL INTRATHECAL ANESTHESIA
• EPIDURAL ANESTHESIA
• NERVE BLOCK AND FIELD BLOCK ANESTHESIA

17. TOPICAL ANESTHESIA
• The topical application of local anesthetics is used to anesthetize the skin,
mucous membranes, or cornea.
• A local anesthetic can be applied to the skin to treat itching caused by
poison , insect bites, eczema, or cutaneous manifestations of systemic
diseases such as chickenpox.
• In is sometimes used to anesthetize the skin before minor surgery. The
topical application of a local anesthetic to mucous membranes
can relieve pain caused by oral, nasal, laryngeal, rectal disorders, or
surgery.

19. INFILTRATION ANESTHESIA
• The process involves injecting an anesthetic directly
into subcutaneous tissue just under the skin.
• Infiltration is used primarily for minor surgical
procedures (e.g, Suturing a wound) or for the removal
of foreign bodies.
• It is also frequently used for dental procedures

21. IONTOPHORESIS
• Local anesthetics can also be administered by
iontophoresis.
• This technique uses a small electric current to force
molecules of the anesthetic into the tissue.
• Iontophoresis is used primarily in dentistry.
• A new, needle-free device with the trade name of
zingo delivers powdered lidocaine by rapid gas pressure
to reduce the pain of subsequent peripheral injections or
blood draws. It is approved for use in children.

23. SPINAL INTRATHECAL ANESTHESIA
• Spinal anesthesia is used to block somatic sensory and motor fibers during procedures such as
surgery on the lower limb or pelvic structures.
• A local anesthetic is injected into the subarachnoid, intrathecal space below the level at which the
spinal cord terminates.
• The spread of the anesthetic along the neuroaxis is controlled by the horizontal tilt of the patient
and by the baricity of the local anesthetic solution.
• Spinal anesthesia can cause headaches associated with cerebrospinal fluid leakage from
the lumbar puncture, and respiratory depression can occur if the anesthetic ascends too high up
the spinal cord. Entry into the CNS by spinal injection also carries a small risk of infection or
meningitis.

25. ADVERSE EFFECTS AND
INTERACTIONS
• Local anesthetics often produce CNS stimulation ,restlessness,
tremor, and euphoria followed by inhibition drowsiness and
sedation.
• Other symptoms of local anesthetic toxicity include headache,
paresthesias, and nausea.
• Higher concentrations can cause seizures followed by coma.

26. • Allergic reactions to local anesthetics are fairly common.
• Patients who have repeated applications of topical
anesthetics are particularly susceptible to sensitization.
• The ester-type anesthetics cause hypersensitivity
reactions more frequently than do the amide-type
anesthetics.

27. REFERENCE
• GOODMAN & GILMAN'S THE PHARMACOLOGICAL BASIS OF
THERAPEUTICS CHAPTER 14. LOCAL ANESTHETICS - WILLIAM A.
CATTERALL AND KENNETH MACKIE
• SHAHI S AND DESHPANDE S: IONTOPHORESIS: AN APPROACH TO DRUG DELIVERY
ENHANCEMENT. INT J PHARM SCI RES 2017; 8(10): 4056-68.DOI: 10.13040/IJPSR.0975-
8232.8(10).4056-68.
• KD TRIPATHI-ESSENTIALS OF MEDICAL PHARMACOLOGY-JAYPEE BROTHERS MEDICAL
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