Opiod Antagonists Flashcards
Where do opioids bind
Receptors in the brain, spinal cord and GI tract
Endogenous like endorphins or exogenous like heroin and morphine
How is opioids inhibited normally
In absence of endorphins, inhibitory neurones w the receptors release GABA which prevents nearby neurones from releasing neurotransmitters like dopamine, serotonin and norepinephrine
What opioid receptors are activated by endorphins
Located in inhibitory neurones
MU, Kappa and delta receptors
When bound they stop inhibitory neurones from releasing GABA so neurones can release dopamine etc
When does NE and serotonin release
Pain processing regions in brain giving brain
Thalamus, brain stem, spinal cord
When does dopamine release
Reward pathway like ventral tegmental area, prefrontal cortex and nucleas accumbens
Calming sensation
Why does morphine cause she
Opioid receptors in GI as well causing n and v and constipation
And in respiration centres in medulla causing resp depression in OD in morphine, heroin
To treat opioid OD
Opioid antagonists like naloxone (rapid onset and short duration), naltrexone, methylnaltrexone, alvimopan
Bind to opioid receptors without activating them = competitive
Naloxone and detects opioid dependency
Chronic user can develop tolerance so more opioid needed to function normally
So when naloxone given, neurone will be understimulated and get withdrawal = anxiety, shivering, tremors, yawning, body aches, diarrhoea, abdominal cramps, runny nose, sneezing, sweating, HR increase and BP
Naltrexone
Duration of 8-12 hrs to prevent relapse - no longer get euphoric feeling
Can be used in recovering alcoholics as alcohol releases endogenous opioids
Methylnaltrexone and alvimopan
Cant cross BBB
Treats GI symptoms like constipation caused by opioid analgesics
And postoperative ileus which decreasing GI motility, worsened by opiate use
