Local anaesthetics Flashcards
What is the general structure of local anaesthetics?
Lipophilic group - intermediate bound (Ester or amide) - hydrophilic group
What is the general mechanism go action of local anaesthetics
Inhibits opened or inactivated voltage-dependent sodium channels. LA binds and blocks the channel.
How are ester LA eliminated?
Ester LA undergo extensive hydrolysis in the plasma by pseudocholinesterase enzymes.
How are amide LA eliminated?
Metabolised by cytochrome P-450 enzymes in the liver.
What effects the potency of LA?
Fiber size, type and myelination. Vasodilator/vasoconstrictor properties. Frequency of nerve stimulation. pH and electrolyte concentration.
How does lipid solubility effect LA?
Have a longer activity due to decreased clearance through localised blood flow and increased protein binding.
Name one LA that is a vasodilator and one that is a vasoconstrictor?
Vasodilator - Lidocaine
Vasoconstrictor - Ropivacaine
How does field block anaesthesia work?
LA is deposited near the larger terminal nerve endings.
How does nerve block anaesthesia work?
LA is deposited close to the main nerve trunk.
