Opioids Flashcards
Which endogenous opioids bind to which opioid receptor?
State the two overall ways opioids act.
Other than analgesia give some effects of activation of the other receptors.
B-endorphins/ Enkephalins - mu opioid
Enkephalins - delta opioid
Dynorphins - kappa opioid
Pre-synaptic - prevent Ca2+ entry
Post-synaptic - cause K+ efflux and hyperpolarisation
Mu - respiratory depression, slow GI motility, sedation, euphoria, miosis, physical dependance
Delta - GI motility (possibly resp depression),
Kappa - diuresis, Dysphoria, (sedation)
Morphine.
Why may gut absorption be even more erratic with people on chronic opioids?
Why may someone with renal failure start to develop seizures on morphine?
Risk with pregnancy?
Why miosis?
Why emesis?
Why should you be cautious with it in asthmatics?
Due to morphine slowing down gut motility
Morphine is conjugated with glucoronide to M3G and M6G.
M6G has an analgesic effect whilst M3G has a convulsant effect since it can cross the BBB. Since M3G is usually regally excreted it builds up and causes seizures.
Gets into foetal tissues and can cause respiratory depression/ dependance in the newborn
Binding to mu receptors in the EWN of the III nerve.
Stimulation of the chemoreceptor trigger zone.
Causes histamine release leading to bronchospasm.
Which side effects are less pronounced in fentanyl?
Metabolised by?
Why may it be an issue with NSAIDs, warfarin etc?
What is it;s increased potency relative to morphine due to?
Bioavailability vs morphine?
Give some routes of admin.
Histamine release
Sedation
Constipation
CYP3A4
Highly protein bound
High lipophilicity and therefore can cross the BBB
80-100% vs ~40%
IV, intrathecal, nasal, epidural, transdermal
Codeine.
Metabolised by what and to?
Two uses?
Common side effects?
CYP2D6 to morphine.
Cough depressant
Mild-moderate analgesia
Constipation
Respiratory depression
Buprenorphine.
Actions at mu kappa and delta receptors.
Why is buprenorphine safe in renal failure patients?
Comment on da Kd and the EMax of the morphine vs the buprenorphine.
Give the side effects of buprenorphine.
Partial agonist, antagonist at the other two.
its because it has billiary excretion mainly.
Kd of buprenorphine is lower due to it having higher affinity
But the Emax is lower and not that of 100% because of the fact it is partial agonist
Respiratory depression
Hypotension
Nausea
Dizziness
Naloxone.
Why very low bioavailability?
Why distributed so fast?
What is it excreted as?
Why can it not be used in buprenorphine overdose?
Why give slow infusion?
This is because of extensive first pass effect and PO ROA.
Because lipophillicity
Naloxone-3-glucoronide
This is because it has affinity of less than buprenorphine
Short half life
Methadone MOA.
binds to opioid receptors with high affinity but low has lower EMax - providing sufficient analgesia - but lower euphoria and respiratory depression.
Give 5 contraindications for opioids.
Opioids are controlled drugs - what does this mean?
Hepatic failure Acute respiratory distress Head injury Raised ICP Coma
CHARH
Date and prescribers/ pt full name and address.
Units, total volume and formulation of drug
Clearly defined drug
