Drugs affecting nerve excitability Flashcards
4 things required for chemical neurotransmission
synthesis/storage
release
inactivation
receptors
2 features of local anaesthetic? Where does it act?
regionalised
no loss of consciousness
acts peripheral nerve
2 features of general anaesthetic?
non-regionalised
LOSS of consciousness
acts central cortex
What happened with cocaine in the eye ball?
reversible numbness
mechanism of action of local anaesthetic?
reversibly block conduction of nerve impulses at axonal membrane via binding of Na+ channel
aminoesters short or long acting? why? example?
procaine
shorter acting
due to hydrolysis by esterases
aminoamides short or long acting? why? example?
long acting
lignocaine, bupivi/ropivi-caine
hepatic metabolism
Is Benzocaine an aminoester? or aminoamide?
neither, is its own class
local anaesthetic affect any nerve?
yes depending on dose (determines effect)
nerve damage with local anaesthetic?
Nope. Reversible binding
sensory or motor knocked out first with epidural anaesthetics?
sensory first, then motor slowly
Where does local anaesthetic bind on sodium channel compared to toxins?
anaesthetic: intracellular
toxins: extracellular
2 mechanisms of anaesthetic interaction with membrane Na+ channel?
hydrophobic: fast, non use dependent
hydrophilic: slow, use dependent
benzocaine is hydrophilic or phobic? fast or slow? properties?
hydrophobic
fast acting non use dependent
aminoesters and amino amides is hydrophilic or phobic? fast or slow? properties?
hydrophilic
slow acting, use dependent
why chew lime with cocaine leaves?
acid helps to neutralize the basic flavour and helps with increased absorption into membrane
sensory fibers small or large?
small
sensory>ANS>motor
what does local anaesthetic do to axon membrane?
stabilize resting membrane potential
local anaesthetic better or worse in basic medium?
basic
better to have charged or uncharged species for local anaesthetic?
both essential
uncharged more active
is hypersensitivity to local anaesthetic proportional to blood level?
Nope, small amount cause big reaction
too much local anaesthetic does what to cardiovascular system?
myocardial depression
vasomotor centre depression
hypotension
cocaine cause hypotension?
Nope
too much local anaesthetic does what to CNS system?
excitation
tremor
convulsion
respiratory arrest
people with more trauma and inflammation need more or less anesthetic?
More because pH lower d/t inflammation
4 stages of general anaesthetics?
- amnesia,euphoria
- excitement
- surgical anaesthesia
- medullary depression
2 ways to administer general anaesthetics?
inhalation
intravenous
2 big side effects of general anaesthetic?
respiratory
Cardiovascular
what is lipid theory of pharmacodynamics of general anaesthetics?
- correlation b/n anaesthetic and lipid solubility
2. meyer-overton: volume expansion of membrane lipids
can you reverse general anaesthetic via pressure?
yes in hyperbaric chamber
what is receptor interaction theory pharmacodynamics of general anaesthetics?
inhibit excitatory receptors like glutamate
enhance inhibitory receptors like GABA
what class of drugs enhance GABA?
benzodiazepines
3 ways to reduce excitatory glutamate?
- limit nerve activation
- inhibit T-type Ca2+channels
- inhibit NMDA receptor
