LOCAL ANAESTHESIA

General Propertiest

Machanism of action

• LAs block both the generation and the conduction of the nerve impulses
• The blockage results from biochemical changes caused by the drug on the lipotropic film of cell membrane.

Pharmacological Actions

1. On CVS :

• Myocardiac depressants
• Heart rate ¯ ed
• Excitability and refractory period are ­
• Produce hypotension

1. On CNS :

• Cause light – headedness, dizziness and blurred vision
• Restlessness, tremors and convulsions
• Higher does causes CNS stimulation followed by depression

1. Other actions :

• Direct spasmolytic action on smooth muscle.
• Can produce neuro-muscular blockade in large doses

Absorption, Fate & Excretion

• LA’s are not absorbed from unbroken sking
• Absorption is more rapid from the trachea than the pharynx while it is poor through the urinary bladder.
• Metabolized by hydrolysis in both liver and plasma.
• The amide like LA’s are degraded by liver microsomes.