Opiate Agonists/Antagonists Flashcards
Endogenous opioid peptides
Enkephalins (met- and leu-)
-5 amino acid sequence with met- and leu- group different at the end
B-Endorphins
-99 amino acids
Dynorphins
^All are released in CNS and GI system in response to stress and pain, have tried to commercially produce them but can’t
Biggest group of opiate receptors found in ____
GI system
Opioid receptors
- mu receptor (MOP)
- delta receptor (DOP)
- kappa receptor (KOP)
Opiate receptors (how they work)
Anti-pain neurons with endorphins or enkephalins will run parallel to pain pathway
-Will attach to presynaptic opiate receptors (opioids=agonists to these receptors) on pain nerves to decrease the amount of pain chemical released
Opioid receptor with the most analgesic effect
Mu
Opioid receptor with dysphoria effect
Kappa, have low abuse potential
Opioid receptor with antishivering effect
Kappa
Opioid receptors with miosis effect
Miosis=pinpoint pupils
Mu and Kappa
Partial opioid agonists (example, what they do)
Ex: Buprenorphine
Act as partial antagonist if given after agonist
If given along acts an as agonist
3 chemical structures of opioids
Phenanthrene alkaloids -Natural -Semisynthetic -Synthetic Piperidine derivatives -All synthetic -Phenylpiperidines (not technically correct but usually they're all referred to as this) -Anilidopiperidines Diphenylheptanes -Methadone *3 different classes are structurally different, if true allergy a cross allergic reaction should happen between classes
Opioids most likely to stimulate the release of histamine
Meperidine (Demerol)
Morphine
Codeine
Semisynthetic phenanthrenes (dilaudid, oxy, etc)
Phenanthrene Alkaloids (common meds we would give)
Naturally occurring -Morphine -Codeine Semisynthetic -Vicodan -Dilaudid -Oxycodone
Piperidine Derivatives (common meds we would give)
Phenylpiperidine: Demerol Anilidopiperidines -Fentanyl -Sufentanil -Alfentanil -Remifentanil
Potency (compared to morphine) of
Demerol: 0.1 Fentanyl: 100 Sufentanil: 500-1000 Alfentanil: 10-20 Remifentanil: 100 Dilaudid: 5 Heroin: 2 (but has more euphoria)
Remifentanil metabolism
Nonspecific esterase enzymes via hydrolysis (needs to be given as a drip)
Demerol metabolism and contraindication
Metabolism
-Metabolized to a toxic metabolite (normaperidine) which is CNS toxic -> seizures
-Don’t use >24 hours or in those with renal disease/elderly, they can’t get rid of the metabolite
Contraindication: Patient taking MAO inhibitors
What effects of opioids do you never develop tolerance to
Constipation and miosis
Do opioids have antitussive effect?
Yes, they all suppress cough which helps during emergence
Narcotics and muscle rigidity
Happens when high potency opioids are administered rapidly
-Especially in older patients when muscle relaxants aren’t used and N2O is given at the same time
Thoracic muscles are rigid, and glottis closure occurs
-Give succinylcholine (it only happens after loss of consciousness, so if it’s happening you know paralytics are OK to give)
Opioid effect on biliary pressure
Opioids have vagal effect on SMC sphincters: tighten them -Including sphincter of odi-biliary tree outlet=biliary pressure buildup -Dose dependent Can treat/reverse with -atropine or glycopyrrolate -nitroglycerine -glucagon -naloxone
Suftenanil use
Giving any dose will result in apnea
-Only use for big/long cases where patient will stay intubated postop
Opioid effect on ICP
Don’t directly increase or decrease it
But, if they cause respiratory depression and CO2 increases, this causes vasodilation and increases ICP
-Doesn’t matter for surgery because we are supporting their respirations
Naloxone mechanism of action
Competitive mu-opioid receptor antagonist
Dosing narcan
0.4-2mg increments (start lower 0.4mg after surgery so you can get respiratory effort back but don’t lose all your analgesia)
Max dose: 10mg
Narcan onset, peak, duration
Onset: 2 minutes
Peak: 5-15 minutes
Duration: 20-60 minutes
