local anaesthetics Flashcards
what do local anaesthetics do
block vgNa+ channels and so stop conduction of APs
what was the first LAs used by South Americans
cocaine
what are the order of LAs produced
cocaine - procaine - lignocaine
what bonds are in procaine and lignocaine
procaine - ester bonds
lignocaine - amide bonds
what was the problem with procaine
we have esterases in our body so we break down procain very quickly - v short half life, so higher concentrations or more frequent doses needed
what are the acidic properties of LAs
they are weak bases
if LAs find itself in more acidic environment what happens
more protons flying around so base accepts protons and more of LA is ionised - can’t cross membranes
(opposite for alkaline environment)
what is the optimum environment of LAs to work
- ion trapping
actions of LA is increased in alkaline pH.
but are more effective at blocking Na+ channels when ionised. (will block when channels are open)
what will LAs that are unionised block
Na+ channels in their closed state
what nerves will be preferentially blocked
higher frequency nerve fibres
what do LAs block first
small diameter axons before large diameter ones and block unmylelinated before myelinated - preferentially blocking nociceptive fibres
whats another CVS symptom of LAs
vasodilation - NA acting on a1 receptors
what does administering with Adrenaline do
help keep LAs localised - adrenaline produces vasoconstriction on alpha 1 receptors on VSMCs
