Analgesic Drugs Flashcards
how do NSAIDs stop pain?
they decrease nociceptor stimulation in inflammation
how do opioids stop pain?
suppress transmission of nociceptive signals in the DORSAL horn of the spinal cord AND
activate descending inhibitory controls
how do anti-epileptics stop pain?
target ion channels that have been upregulated in nerve damage
difference between opiate and opioid?
an opiate is a substance attracted from opium ONLY whereas an opioid is any agent that acts upon opioid receptors
what can stop pain from ascending the spinal cord?
inhibitory interneurones
what fibres excite inhibitory interneurones?
A-beta fibres
low threshold mechanoreceptors
what fibres suppress inhibitory interneurones (thus allowing nociceptive input to ascend the spinal cord and cause pain)?
C fibres
A-delta fibres
all primary sensory afferents are excitatory T or F
T
where is nociceptive input inhibited by fibres?
dorsal horn of the spinal cord
what parts of the brain are involved in pain perception and emotion?
cortex
amygdala
thalamus
hypothalamus
then project input to the BRAINSTEM
the periaqueductal grey is located where in the brainstem?
midbrain
what does the periaqueductal grey do?
causes descending inhibition which presents nociceptive input reaching the thalamus
opioids _regulate the activity of the preriaqueductal grey
up
what part of the brainstem inhibits noradrenaline?
locus coeruleus
what part of the brainstem inhibits 5-HT and thus serotonin?
nucleus raphe magnus
all opioids act on what receptors?
GPCRs
what G-proteins do opioids act on?
Gi
Go
opioids ___ voltage-activated Ca channel opening; why?
inhibit
stops glutamate release thus dampening down nerve conduction
opioids ___ K+ channel opening; why?
upregulate
will cause more hyperpolarisation thus will dampen down the excitatory response
what type of opioid receptor is responsible for most of the analgesic action of opioids?
μ receptors
resp side effects of opioids?
apnoea
bronchospasm in asthmatics
GI side effects of opioids?
N+V
constipation
inc intrabiliary pressure
morphine is metabolised in the liver by what process?
glucorinidation
diamorphine has a __ onset of action
fast
pethidine is mainly used for what kind of pain?
pain in labour
MoA of tramadol
μ-receptor agonist
tramadol should be avoided in what patients?
epileptic
methadone is given via what route?
oral
what is the main opioid antagonist used to counteract opioid toxicity?
naloxone IV
morphine should be carefully used in what patients?
addicts
asthmatics
patients with kidney disease
COX enzymes catabolise what?
arachidonic acid into endoperoxides (to make prostaglandins)
diamorphine is another word for what compound?
heroin
in order to suppress production of prostaglandins in the dorsal horn of the spinal cord, NSAIDs must do what first?
cross the BBB
