Anaesthetic Flashcards
How does general anaesthetic work
Blocks presynaptic calcium entry, decreasing neurotransmitter release at the synapse
How does local anaesthetic work
Conduction block, decreases axonal sodium entry and decrease AP propagation
Structure of LA drug
Aromatic region + ester or amide bond + basic amine side chain
Does amide or ester bonded LA drug have a longer half life
Amides have a longer half life because they are more stable
Esters hydrolysed rapidly
Amide LA lasts longer because more stable, metabolized more slowly, longer half life
3 states of sodium channel
Resting open inactive
When is the refractory period of sodium channels
From the inactivated state to the resting state
Where does LA bind on the sodium channels
Binds intracellular side, blocks channel and stabilised it in inactivated form, preventing sodium influx
How does LA get to the intracellular side in cells
Diffuse across nerve cell membrane because it has an aromatic group
What is the half life of ester vs amide linked LA
Ester less than 3 min
amide 1-3 hours
Where are LA metabolized
Ester - tissue and plasma cholinesterases
Amide - slowly in the liver by P450 enzymes
What determines the hydrophobicity and charge in LA
Hydrophobicity - aromatic group
Charge - basic amine side chain
The more ionised the LA, the harder or easier to diffuse through the nerve cell membrane ?
Harder because more soluble
LA should be lipophilic to penetrate nerve membranes and block the conduction of nerve signals
Most common dental LA
Lidocaine and articaine
What is anaesthetic often injected with
Vasoconstrictor like adrenaline to prevent LA from running into systemic circulation
