How local anesthetic work
Spinal cord anesthesia
Local anesthesia is defined as a loss
of sensation in a circumscribed area of the
body caused by depression of excitation in
nerve endings or an inhibition of the conduction
process in peripheral nerves
LOSS OF SENSATION WITHOUT
INDUCING LOSS OF CONSCIOUSNESS.
Altering the basic potential of nerve membrane
Altering the threshold
Decreasing the rate of depolarization
Prolonging the rate of repolarization
Local anesthetics inhibit depolarization of the
nerve membrane by interfering with both Na+ and
The action potential is not propagated because
the threshold level is never attained.
Local anesthetics act at the cell membrane to
prevent the generation and the conduction of
Following injection into the area of nerve fibers to be
blocked, local anesthetics are absorbed into blood.
Ester-linked local anesthetics are quickly hydrolyzed
by butyrylcholinesterase in blood.
Amide-linked local anesthetics can be widely
distributed via circulation. Amide- linked local
anesthetics are hydrolyzed by liver microsomal
Thus, half lifes of these drugs are significantly longer
and toxicity is more likely to occur in patients with
impaired liver function.
Absorption of local anesthetics is affected by
– site of injection
– drug-tissue-binding and
– Presence of vaso-constricting drugs
Prevention and treatment of cardiac arrhythmias
Prevention/management: increased intracranial
Treatment of grand mal seizure
Low doses: tremors and oral numbness,
with possible dizziness, confusion and
agitation (exception = cocaine)
Mod. doses: convulsions (immediately
preceded by muscle twitching); prevented by
injection of anti-convulsant
High doses: possible respiratory depression
vasodilation (exception = cocaine)
- less often, myocardial depression
- ventricular contraction possibly leading to
reduced cardiac output,
in the worst case, ventricular arrhythmias and
arrest unintentional high plasma levels of LAs, but
can occur with normal IV doses of bupivacaine
local dermatitis with some topical; rare
systemic allergic response with injected
esters (due to metabolite)
• Depress contractions in the intact bowel
• Relax vascular and bronchial smooth muscle
• May increase the resting tone
• Decrease the contractions of isolated human
Cocaine, an ester of benzoic acid and
methylecognine, occurs in abundance in the
leaves of the coca shrub.
Cocaine produces anesthesia by inhibiting
excitation of nerve endings or by blocking
conduction in peripheral nerves. This is achieved
by reversibly binding to and inactivating sodium
channels. Sodium influx through these channels is
necessary for the depolarization of nerve cell
membranes and subsequent propagation of
impulses along the course of the nerve.
Cocaine is the only local anesthetic with
This is a result of its blockade of norepinephrine
reuptake in the autonomic nervous system.
Cocaine binds differentially to the dopamine,
serotonin, and norepinephrine transport proteins
and directly prevents the re-uptake of dopamine,
serotonin, and norepinephrine into pre-synaptic
neurons. Its effect on dopamine levels is most
responsible for the addictive property of cocaine.
Cocaine is absorbed from all sites of application,
including mucous membranes and gastrointestinal
mucosa. By oral or intra-nasal route, 60 to 80% of
cocaine is absorbed.
Hepatic. Cocaine is metabolized to
benzoylecgonine and ecgonine methyl ester,
which are both excreted in the urine.
For the introduction of local (topical) anesthesia of
accessible mucous membranes of the oral,
laryngeal and nasal cavities.
A local anesthetic and cardiac depressant used as
an anti arrhythmia agent.
Its actions are more intense and its effects more
prolonged than those of procaine.
its duration of action is shorter than that of
bupivacaine or prilocaine.
Mechanism of action
Lidocaine stabilizes the neuronal membrane by
inhibiting the ionic fluxes required for the initiation
and conduction of impulses thereby effecting local
anesthetic action. Lidocaine alters signal
conduction in neurons by blocking the fast voltage
gated sodium (Na+) channels in the neuronal cell
membrane that are responsible for signal
With sufficient blockage the membrane of the
postsynaptic neuron will not depolarize and will
thus fail to transmit an action potential. This
creates the anesthetic effect by not merely
preventing pain signals from propagating to the
brain but by aborting their birth in the first place.
information derived from diverse formulations,
concentrations and usages reveals that lidocaine
is completely absorbed following parenteral
administration, its rate of absorption depending,
for example, upon various factors such as the site
of administration and the presence or absence of
a vasoconstrictor agent.
Route of elimination
Lidocaine and its metabolites are excreted by the
convulsions, hypoxia, acidosis, bradycardia,
arrhythmias and cardiac arrest
For production of local or regional anesthesia by
infiltration techniques such as
percutaneous injection and
intravenous regional anesthesia
by peripheral nerve block techniques such as
brachial plexus and intercostal and by central
neural techniques such as lumbar and caudal
Dyclonine is an oral anesthetic found in Sucrets,
an over the counter throat lozenge.
It is also found in some varieties of the Cepacol
sore throat spray.
Mechanism of action
Local anesthetics block both the initiation and
conduction of nerve impulses by decreasing the
neuronal membrane's permeability to sodium ions.
This reversibly stabilizes the membrane and
inhibits depolarization, resulting in the failure of a
propagated action potential and subsequent
Readily absorbed through mucous membranes
into the systemic circulation.
Approximately 30 to 60 minutes.
cardiovascular system depression, CNS toxicity,
Used to provide topical anesthesia of accessible mucous
membranes prior to examination, endoscopy or
instrumentation, or other procedures involving the
esophagus, larynx, mouth, pharynx or throat, respiratory
tract or trachea, urinary tract, or vagina.
Also used to suppress the gag reflex and/or other
laryngeal and esophageal reflexes to facilitate dental
examination or procedures (including oral surgery),
endoscopy, or intubation.
Also used for relief of canker sores, cold sores or fever
Anesthesia of mucous membrane of nose, mouth
throat can be produced by direct application of salts of
many local anesthetics or by suspension of poorly
soluble drugs like tetracain 2 % or lidocain2 %
It is the injection of local anesthetic directly into
the tissue without taking into consideration the
course of nerve
Is produced by SC injection of a solution of LA in
order to anesthetize the region distal to the
injection of a LA into or about individual peripheral
nerve or peripheral plexuses.