LA Flashcards
what is LA Moa
stop axonal conduction by blocking sodium channels in the axonal membrane –> prevent sodium ion entry –> slow down or bring conduction to a halt
non-selective modifiers of neuronal function
Use dependency of LA
depth of LA nerve block increases with action potential frequency because LA
gain access to the channel more readily when channel is open
higher affinity for the inactivated than for the resting channels
more ____ double drugs are more potent and act ________
lipid, longer
name 3 more hydrophobic LA
tetracaine, etidocaine, bupivacaine
name 3 less hydrophobic LA
lidocaine, procaine, mepivacaine
effect on the size of nerves
smaller > bigger
effect on frequency of firing
high (sensory) > low (motor)
effect on position of nerves
circumferential > deep (large nerve trunk)
effect of myelination on LA activity
myelinated > nonmyelinated
effect of pH
LA molecules are week bases, mainly but not completely ionised at physiological pH
alkaline pH –> increased LA activity (proportion of ionised molecules low)
acidic: other way around
ester type Characteristic chemistry: representative agents: incidence of allergic reaction: method of metabolism:
ester bond
procaine
low
plasma/tissue non-specific esterase’s
amide type Characteristic chemistry: representative agents: incidence of allergic reaction: method of metabolism:
amide bond
lidocaine
very low
hepatic enzymes
LA is absorbed by a __ compartment model
2
phase one of absorption is due to the ____ distribution to _________
rapid
highly perfused organs (brain, liver, heart, kidney)
phase 2 of absorption is due to the ____ distribution to ____
slower
less well perfused (muscle, gut)
anaesthetics that penetrate the ____ faster have the fastest onset
___ size
high____ solubility
____ ionisation
axon
small
lipid
low
how do you accidentally OD (2)
accidentally inject IV or intra arterial
locally but the dose too high
how to prevent OD of LA
combine with epi –> prevent systemic distribution from the site of action
______ is more cardiotoxic than most other LAs
bupivacaine
_____ blocks NA reuptake, increased NA causes _______ and __________
cocaine
vasoconstriction and hypertension
_____ (metabolite of prolicane) causes ________
o-toluidine
methaeglobin
ester LAs are hydrolysed to ______ which cause allergic reactions
PABA
topical applications of LA
skin eye dental otorhinolaryngology gynaecology
injected applications of LA
epidural (lidocaine, bupivacaine)
dental
injected dental
lidocaine (_____ acing)
bupivacaine (____ acting)
may combine with ______ –> why?
short
long
epi –> vasoconstrictor –> control bleeding
____ used most for ENT because ______
cocaine
good penetration and vasoconstriction
