& IT’S ACTION
Local anesthetic solution
Prepared by Dr. Fatima Abdhamed Yaffai
Local anesthesia Local anesthesia has been defined as
a loss of sensation in a circumscribed area of the body caused by a depression of
excitation in nerve endings or an inhibition of conduction process in peripheral nerves.
Local anesthetic: produce loss of sensation to pain in a specific area of the body without the
loss of consciousness
Solution contained
within a dental cartridge
1. Local anesthetic solution
2. Vasopressor
3. Sodium chloride
4. Distilled water.
Action of local anesthetic
The concept
They prevent both the generation and the
conduction of a nerve impulse.
It sets up a chemical roadblock between
the source of impulse (e.g. the scalpel incision in soft tissues) and the
brain.
Physiology of the peripheral nerves.
The function of a nerve is to carry messages from one part of the body to another. These
messages, in the form of electrical action potentials,
are called impulses.
Action potentials are transient membrane depolarization that result from a brief increase in
the permeability of the membrane to sodium, and usually also from a delayed
increase in the permeability to potassium.
Mode and site of action of local anesthetics
The nerve membrane is the
site at which local anesthetic
agents exert their
pharmacological actions.
The primary action of local anesthetic in producing a conduction block is to decease the permeability of the ion
channels to sodium ions (N+)
• All local anesthetics are amphipathic,• Local anesthetics without a hydrophilic part
are not suited for injection but are good topical anesthetics.
• The nature of the linkage is important in defining several properties of the local anesthetic, including the basic mode of
biotransformation.
Local anesthetic are availabe as salts for clinical use. Within the solution it exists simultaneously as
1.Uncharged molecules (RN) also called the base and
2. positively charged molecules (RNH+), called the cation.
RNH+ RN + H+
The uncharged, lipid-soluble, free base form (RN) of the anesthetic is
responsible for diffusion through the nerve sheath.
In the presence of a high concentration of hydrogen ions (low pH) the equilibrium shifts to the left and most of the anesthetic solution
exists in cationic form.
RNH+ > RN + H+
As hydrogen ion concentration decreases (higher pH), the equilibrium shifts toward
the free base form. RNH+ < RN + H+
Local anesthetics
Esters
Esters of benzoic
acid
ButacaineCocaine
BenzocaineHedylcainePiperocain
eTetracaine.
Esters of para-
aminobenzoic acid
Chloroprocaine
Procainepropoxycaine
Amides
ArticaineBupivacain
eDibucaineEtidocaineLidocaine Mepivacain
eprilocaine
Quinoline
centbucridine
the doses of local anesthetic drugs are presented in terms of milligrams of drug
per unit of body weight, mg/kg. Maximum dose for an individual is usually between 70mg to 500mgThe amount of dose also varied based on the type of solution used and the presence of vasoconstrictor
Example:---For adult whose weight is 150lbs and up, maximum dose Articaine and lidocaine is about 500mg---For children, the dosage reduced to about 1/3 to ½ depending on their weight.
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