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Module 6 Local Anesthetics By Lauren McCormick (History (first synthetic…
Module 6
Local Anesthetics
By Lauren McCormick
History
first local anesthetic = cocaine, 1880's
first synthetic local anesthetic = procaine (Novocain), 1904
first class of ester local anesthetics
Lidocaine (Xylocaine), 1940's
Types
Esters
Procaine
Cocaine
Tetracaine (Pontocaine)
Benzocaine
Chloroprocaine
Metabolism
metabolized in plasma by plasma pseudocholinesterase
product of procaine degradation
para-aminobenzoic acid (PABA)
common ingredient in topical sunscreens
provokes allergic reaction
likely agent for the rare cases of allergic reaction
Amides
Lidocaine (Xylocaine, Octocaine, alphacaine)
Bupivacaine (Macaine, Sensorcaine)
Mepivacaine (Carbocaine, Polocaine)
Prilocaine (Citanest)
Articaine (Septocaine, Carticaine, Ultracaine)
Metabolism
far less likely to produce allergic reaction
Atypical Drugs
Dyclonine hydrochloride
local anesthetic found in throat lozenges
Diphenhydramine
antihistamine used as local anesthetic (if others are intolerable)
if patient is allergic to both esters and amides
true allergic rxns are rare
usually involve esters, rarely amides
most likely represent misinterpretation of symptoms
vasovagal reaction
effect of epinephrine
intravascular injury
typically due to PABA-like preservatives used in ester compounds
try 1cc hypdermic test injection to evaluate antigen reaction
no cross reactivity between amide and ester agents
it pt is allergic to one, a different class may be substituted
Benadryl
may cause more pain on infiltration
less effective
greater risk of tissue necrosis
Method of Action
reversibly blocking nerve conduction
reduces influx of sodium ions into nerve cytoplasm
potassium ions therefore cannot flow out
depolarization of nerve is inhibited
penetrates nerve membrane