Opioids Flashcards
Three opioid receptors opioids act on
Mu
Kappa
Delta
Most important opioid receptor for opioids
Mu
Opioid receptor which mediates euphoria
Mu
Opioid receptor which mediates respiratory depression
Mu
Opioid receptor which mediates dependence
Mu
Opioid receptor which mediates anxiolysis
Delta
Opioid receptor which mediates constipaton
Mu
Effect of mu stimulation on dopamine
Results in dopamine release from the ventral tegmental area producing euphoria
Effect of repeated opioid use on dopamine release
Mu receptors in the ventral tegmental area become less receptive
Less dopamine is released
Half life of methadone
15-22 hours
Affinity of buprenorphine for the mu receptor compared to morphine
5x higher
Half life of buprenorphine
24-42 hours with oral administration
Half life of naloxone
30-120 minutes
Serious respiratory adverse effect of naloxone
Non-cardiogenic pulmonary oedema
Half life of naltrexone
4-6 hours
Half life of the active metabolite of naltrexone
13 hours
Length of time someone needs to have been opiate free for naltrexone to be licensed
7-10 days
Active metabolite of naltrexone
6-βnaltrexol
Half life of morphine
2-3 hours
Half life of heroin
2-3 minutes
Effect of starting buprenorphine if already taking opioids regularly
Can precipitate mild-moderate withdrawal - much more affinity for receptors than full agonists so displaces them
Opioid withdrawal effects improved by alpha 2 adrenergic agonists (clonidine and lofexidine)
Sweating
Shivering
Runny nose
Watery eyes
Antihypertensive effect of clonidine compared to lofexidine
Lofexidine has a lower antihypertensive effect
Mechanism of action of withdrawal symptoms of jitteriness, muscle cramps, diarrhoea etc.
Locus coeruleus has a lot of noradrenargic neurons that have mu receptors
Exposure to opioids results in heightened activity of these neurons but the opioids themselves suppress activity
If there are no longer opioids present to suppress the activity increased amounts of norepinephrine are released
