Local Anesthesia

Question 1

MOA LA

Answer 1

-Reversibly block impulse conduction along nerve axons
-Block sodium channel for conduction
-inhibit: substance P, NMDA & AMPA receptor, nicotinic acetylcholine channels

Question 2

Classification of LA

Answer 2

Ester (slow onset of action)
-cocaine
-procaine
-benzocaine

Amide (faster onset of action)
-Lidocaine
-bupivacaine
-prilocaine
-dibucaine

Question 3

Vasoconstrictor (adrenaline/epinephrine)

Answer 3

-reduces systemic absorption of LA
-reduces systemic toxicity
-prolong LA action by acting Alpha-1 adrenoceptors
-less effective for long-acting LA

Question 4

Unwanted effects

Answer 4

-myocardial depression
-vasodilation

Cocaine: tachycardia, increase cardiac output, vasoconstriction, increased atrial pressure

Prilocaine: methamoglobinemia
Antidote: methylene blue/ascorbic acid

Lignocaine: muscle twitching, convulsions, cardiac arrhythmia, fall BP, coma, respiratory arrest.
Antidote : vasoconstrictor (adrenaline)

Uses:
Eutectic mixture: 2.5% prilocaine +2.5% lignocaine for intact skin

Question 5

Uses of LA

Answer 5

Dental procedure
Obstetric, orthopedic procedure
Topical LA for eye, nose and throat
IV administration of lidocaine for the management of ventricular arrhythmia