Opioids Flashcards
what do opioids do for level of wakeness and pain
General anesthetics produce unconsciousness but do not inhibit pain signal generation or propagation
why do patients not feel mildly painful surgical manipulations
Patients do not feel mildly painful surgical manipulations (e.g., a skin incision) simply because the small numbers of pain signals, which are transmitted to the Reticular Activating System (RAS) in the medulla, are insufficient to awaken the patient
how do we prevent the RAS from being stimulated to the point that an anesthetized patient wakes up?
We can prevent this by administering an analgesic beforehand to inhibit pain signal generation
is it safe to administer analgesic before anesthetic? why?
This is safer than trying to maintain unconsciousness using higher doses of general anesthetic (which inhibits respiration & CVS function in a dose dependent manner)
four things opioid drugs are used for
-analgesia; management of moderate to severe pain
-sedation
-cough suppressant (antitussive)
-treatment of diarrhea (constipation is a major side effect)
what three opioid receptor families mediate analgesia
mu (MOR)
delta (DOR)
kappa (KOR)
what one of the opioid receptor families produces dysphoria
sigma
what is the mechanism of opioid receptors
Opioids stimulate opioid receptors in pain pathways
K+ channels open which causes hyperpolarization and then inhibition of APs
also inhibition of calcium entry which inhibits NT release
main effect of MOR stimulation, and others
analgesia; full stimulation causes intense analgesia effects
-euphoria
-miosis or mydriasis
-respiratory depression
main effect of KOR stimulation, and others
analgesia; moderate effect, and primarily visceral
-negligable respiratory depressive effects
what opioid receptor mediated respiratory depression
Mu receptor
difference between full vs partial agonists
full = opioid maximally stimulates opioid receptor
partially = opioid weakly stimulates opioid receptor
what makes a mixed agonist/antagonist
some opioids are agonists at some opioid receptors and antagonists at others
what type of agonist is fentanyl and what effect does it have
Fentanyl is a full mu agonist = produces an intense analgesic
effect via MOR
what type of agonist is butorphenol and what effect does it have
Butorphanol is a kappa agonist
with mild to moderate analgesic
effect
It also very weakly stimulates Mu
receptors, acting as a competitive
antagonist to full Mu agonists
what is the analgesic effect of butorphenol and fentanyl combined
weaker analgesia than with fentanyl alone
primary effect of
what drugs have a mu receptor and what are their interactions
codeine, morphine, hydromorphone, meperidine, fentanyl (all agonists)
buprenorphine and butorphenol (partial agonist)