Local anesthetics (LA) 1

Question 1

Classify local anesthetics chemically?

Answer 1

> Ester local anesthetics:

1- Metabolized by Pseudocholienestrase enzyme of liver and plasma
2- Metabolized into PABA which increase risk of hypersensitivity.
3- have short duration of action
4- slow onset

> Amide local anesthetics:

1- Metabolized by hepatic Microsomal enzymes in the liver
2- longer duration of action than ester LA
3- Faster in onset
4- Lower risk of Hypersensitivity
5- Higher risk for systemic toxicity

Question 2

Enumerate Ester local anesthetics?

Answer 2

P.C.B.T بكبت احزاني
Procaine
Cocaine
Benzocaine
Tetracaine

Question 3

Enumerate Amide local anesthetics?

Answer 3

Medium action: Lidocaine.
Long action: (Bupivacaine, Dibucaine,
Mepivacaine) ( B.M.D)

Question 4

Mechanism of action of local anesthetics (LA)?

Answer 4

1. Blocking of voltage gated Na+
   channels => inhibit the generation of action potential “Membrane stabilizing effect” that block nerve conduction of sensory impulses from periphery to CNS. (main mechanism)
2. Reduce membrane permeability of the nerve to potassium ions.
3. Compete with Ca++ at some receptor sites.

Question 5

Mention the function of Ionized and un Ionized form of LA at physiological pH of tissue?

Answer 5

I. Un-Ionized form => lipophilic form responsible for penetration through membrane of sensory nerve

II. Ionized form => Hydrophilic → block Na+ channels from inner side of the membrane to prevent generation
of action potential

Question 6

Give reason: Acidosis (caused by inflammation at a wound, abscess) partly reduces the action of LAs?

Answer 6

because most of the
anesthetic will be present in the ionized form and therefore unable to cross the cell membrane to reach its
cytoplasmic site of the sodium channel

Question 7

Mention the pharmacological (systemic) actions of LAs on CNS ?

Answer 7

1. Initial stimulation in the form of restlessness, tremors, and convulsions
2. Overstimulation of the CNS is followed by depression (medullary paralysis with respiratory and circulatory failure → death)
3. Cocaine is powerful cerebral cortex stimulant causing euphoria and addiction.

Question 8

Respiratory failure can be treated with?

Answer 8

artificial respiration

Question 9

Convulsions treated by?

Answer 9

diazepam

Question 10

mention the drug: that cause on
CNS : powerful cerebral cortex stimulant causing (euphoria and addiction)

CVS: vasoconstriction and hypertension and inhibit neuronal uptake of NE (Indirect sympathomimetic activity).

Answer 10

Cocaine