drugs affecting the nervous system Flashcards
what is the nervous system?
CNS - brain and spinal cord
PNS - nerves
what can happen to left over neurotransmitter in the synapse?
taken back into cell via reuptake receptors
broken down by enzymes
list 5 excitatory neurotransmitters
noradrenaline dopamine serotonin (5-HT) acetylcholine glutamine
name 2 inhibitory neurotransmitters
GABA
glycine
name 6 drugs that act mainly on the nervous system
anaesthetics anxiolytic/hypnotic neuromuscular blocking antidepressants antiparkinsonian anticonvulsants
where do general anaesthetics mainly act?
nervous system
via what route can anaesthetics be given?
inhalation
intravenously
why are anaesthetics used?
to promote: analgesia unconsciousness amnesia loss of reflexes
what happens if you have too much anaesthetic?
adverse effects or death
what 3 things can drugs in the brain do?
modify info carried to brain or within brain
alter release of neurotransmitters
open and close ion channels needed for impulse transmission
how can drugs act on the CNS?
promotes insensitivity which means blood is insensitive to incoming signals - depresses reticular activating system and cerebral cortex
are drugs which act on the brain fat soluble? and what does this mean can occur?
drugs that act on the brain are usually fat soluble- this means they can cross the blood- brain barrier
what happens when membrane receptors in the brain are acted upon by drugs?
reduces excitability of neurones
what membrane receptor does propofol bind to?
GABA receptor
what happens if ion channels in the brain are affected by drugs?
changes the fluidity of the cell membrane
what are the typical side effects of anaesthetics?
nausea/vomiting breathing shallow/rapid reduce blood p/CO reduced kidney profusion loss of temp control crosses placenta
name some drugs that interact with anaesthetics
aspirin
anticoagulants
name a drug that should be continued with anaesthetic
steroid drugs
in what conditions should anaesthetics be used with caution?
CVD
hypotension
shock
name the two phases of anaesthesia and how this is achieved
induction - IV (quick/not controllable)
maintenance - inhaled (oxygen needed/facemask)
describe the 4 stages of anaesthesia
stage 1 - analgesia
stage 2 - excitement
stage 3 - surgical anaesthesia - skeletal muscle relaxation/ loss of reflexes
stage 4 - medullary paralysis- loss of respiratory/ vasomotor control
name 4 types of general anaesthetic
barbiturates (contain bartituric acid)
non - barbiturates
gases
volatile liquids
what is nitrous oxide used for?
maintaining anaesthesia - not potent enough to induce general anaesthesia
used as analgesia during child birth
can be used in combination with other drugs
can nitrous oxide damage the foetus in pregnancy?
with low level long term exposure
name 3 inhaled anaesthetics and describe how they work
isoflurane - doesn’t depress CV system, relaxes muscles
desflurane - irritates airways and increases secretions
sevoflurane - rapid onset and recovery
when using inhaled anaesthetics how is the depth of anaesthesia controlled?
by varying the concentration of drug in the vapour
what are the side effects of isoflurane, desflurane and sevoflurane
CV depression
hypotension
arrhythmias
can reduce CSF pressure
what is etomidate? and are its pros and cons?
etomidate - general anaesthetic
pros - no hangover/ less hypotension
cons - muscle movements/ suppression of adrenocortical function
what is ketamine? and what are its pros and cons?
ketamine - general anaesthetic
pros - may be used in children / shocked patients
cons - increased HR + BP/ bad dreams or hallucinations on recovery
care should be taken when administering general anaesthetics to children, why?
risk of bronchospasm and aspiration of fluid
name two commonly used intravenous anaesthetics
propofol - non barbiturate
thiopental - barbiturate
what is propofol? and what are its pros and cons?
propofol - intravenous anaesthetic
pros - rapid action / rapid recovery without hangover
cons- convulsions / anaphylaxis / bradycardia
what is thiopental? what are its pros and cons?
thiopental - intravenous anaesthetic
pros - useful for brief procedures (last 5-10mins)
cons - rapid awakening / long lasting sedation (effects present up to 24hrs later)
what are benzodiazepines? and what routes can they be given via?
anxiolytics/ hyponotics
routes - oral, IV, IM, rectal
name three benzodiazepines and suggest some uses
midazolam - pre med / can be used for children
temazepam - dental treatment / short acting / little hangover
diazepam (valium) - widely used for anxiety / not for children
what are the draw backs of benzodiazepines?
no analgesic effect
causes hypotension / constipation
name six drugs used in surgery and their uses
anxiolytics - calm before surgery
hypnotics - increase reaction time
neuroleptics / anti emetics - induce artificial hibernation
analgesics - pain relief
antihistamines - block histamine
anticholinergics (atropine/ hyoscine) - regulates breathing
explain the mechanism of action for anxiolytic drugs
end aim - to increase GABA (inhibitory neurotransmitter) in the brain
anxiolytics cause inhibitory neurone to release GABA at synapse - this makes post synaptic neurone less excitable and neurones less easily activated
what are the disadvantages of hypnotics?
dependence
respiratory depression
benzodiazepines interact with alcohol
cross placenta
what patients should not be given hypnotics?
patients in shock
what are neuromuscular drugs?
muscle relaxants
how do neuromuscular drugs work?
block transmission in motor nerves
what do neuromuscular drugs reduce the need for?
very deep anaesthesia
how do neuromuscular drugs allow insertion of a tracheal tube?
relax the vocal cords
what is required when using neuromuscular drugs?
assisted respiration - as muscle used in breathing relax
what are some of the disadvantages of using neuromuscular drugs?
prolonged muscle paralysis/ pain
histamine release - bronchospasm etc.
name two types of neuromuscular blockers
non-depolarising blockers (ACh antagonists) depolarising blockers (ACh agonists)
explain the mechanism of non-depolarising blockers
compete with ACh for nicotinic receptors at NMJ - prevents action potential development in muscle
give two examples of non-depolarising blockers
atracurium - rapid, short action
pancuronium - longer acting
how would the action of non-depolarising blockers be reversed?
increasing ACh concentration by inhibiting acetylcholinesterase
name a drug that would inhibiting acetylcholinesterase
neostigmine
explain the action of depolarising blockers
mimic ACh but produce sustained depolarisation of muscle - paralysis
give an example of a depolarising blocker
suxamethonium - short action unless given via drip
how is the action of depolarising blockers reversed?
metabolised by pseudocholinsterase enzyme present in NMJ
1 in 2000 people don’t have pseudocholinsterase enzyme, what would happen in this situation?
prolonged paralysis
what are narcotic (opioid) analgesics and where do they act?
powerful pain kills which act directly on opioid receptors in the CNS (brain)
what feeling is often achieved when taking narcotic (opioid) analgesics?
euphoria - allows escape from reality
give 4 examples of narcotic (opioid) analgesics
fentanyl
alfentanil (rapifen)
remifentanil
morphine - post op.
what are the disadvantages of using narcotic (opioid) analgesics?
nausea/vomiting
reduced breathing rate
risk of addiction
what are local anaesthetics used for?
analgesia
paralysis
(used mainly in minor surgical procedures)
what is the mechanism of action for local anaesthetics?
blocks transmission of nerve impulses carrying pain signals from nociceptors to the brain
at a cellular level what is the mechanism of action for local anaesthetics?
inhibits Na+ entry through v. sensitive Na+ channels - blocks transmission of nerve impulses (depolarisation of cell can not occur)
what are the common methods of administration for local anaesthetics?
epidural - injection into epidural space (affects nerve roots)
intradermal/ topical - relieves minor irritation/ superficial pain
name 5 common used local anaesthetics and when they would be used
lidocaine - widely used/ dental surgery/ treats premature ejaculation
priloxaine - mixed with lidocaine for EMLA cream
bupivacaine
ropivacaine
proxymetacaine
what are the side effects of local anaesthetics and why might they occur?
caused by anaesthetic reaching the brain or heart
- abnormal heart beat
- restlessness
- convulsions
- cardiac arrest (severe cases)
why are vasoconstrictors used in combination with local anaesthetics?
- enhance potency and prolong duration of action - by restricting blood flow to area less anaesthetic is needed
- increase safety margins (reduce toxicity)
- reduced blood flow during surgery lessens blood loss
name a vasoconstrictor which is commonly used in combination with local anaesthetics
adrenaline
how do antidepressants work in the nervous system?
increase levels of excitatory neurotransmitters in the brain
how do antiparkinsonian drugs work in the nervous system?
increase levels of the neurotransmitter dopamine
how do anticonvulsants work in the nervous system?
treat epilepsy by reducing conduction of excitatory nerve impulses and/or increasing GABA activity
name three types of antidepressants
tricyclic antidepressants (TCAs) selective serotonin re-uptake inhibitors (SSRIs) monoamine oxidase inhibitors (MAOIs)
what is the mechanism of action of tricyclic antidepressants (TCAs) and selective serotonin re-uptake inhibitors (SSRIs) antidepressants?
inhibit re-uptake of NADR (noradrenaline), 5-HT (serotonin) or DA (dopamine) into the presynaptic receptor
what is the mechanism of action of monoamine oxidase inhibitors (MAOIs) antidepressants?
inhibits enzyme breakdown of 5-HT (serotonin) and NADR (noradrenaline)
give three examples of tricyclic antidepressants (TCAs)
imipramine
nortriptyline
doxepin
what are the side effects of tricyclic antidepressants (TCAs)?
dry mouth blurred vision constipation urinary retention arrhythmias mental confusion and sedation
give 4 examples of selective serotonin re-uptake inhibitors (SSRIs) antidepressants
fluoxetine
citalopram
sertraline
paroxetine
what are the side effects of selective serotonin re-uptake inhibitors (SSRIs)?
headache nausea dizziness diarrhoea convulsions
give 2 examples of monoamine oxidase inhibitors (MAOIs) antidepressants
phenelzine
tranylcypromine
what are the side effects of monoamine oxidase inhibitors (MAOIs) antidepressants?
nausea
dizziness
insomnia
what do monoamine oxidase inhibitors (MAOIs) antidepressants interact with?
tyramine-containing foods (red wine, cheese, marmite)
what is monoamine oxidase?
an enzyme which breaks down amine neurotranimitters
how does inhibiting monoamine oxidase alter mood?
inhibiting the break down of neurotransmitters keeps them in the brain for longer
