Opioid Antagonists Flashcards
All opioid antagonists are
mu receptor antagonists and competitive antagonists
naloxone is a _____ selective antagonist
non selective; acts on all three opioid receptors
most significantly, naloxone can
reverse opioid RD in neonates and antagonize volatile anesthetics at high doses
naloxone is safe in ____ and ____ shock because it will increase myocardial contractility
septic and hypovolemic
dont give naloxone quick - give over
2-3 minutes
naloxone duration
30-45 mins - so may need redosing
significant s/e of naloxone
NV, reversal of analgesia, increased SNS response causing potentially fatal v fib and pulm edema
naltrexone is more effective
PO
naltrexone is helpful in
alcoholism
naltrexone has a duration of
24 hours
nalmefene is equipotent to
naloxone
naloxone is more 5 times more effective
IV than PO
nalmefene 1/2 time
10.8 hours
list the unique traits of methylnatrexone
highly ionized and works more peripherally; promotes gastric emptying and antagonizes N/V; does not alter central analgesia
list the unique traits of alvimopan
post op ileus; mu selective PO –> acts peripherally; metabolized in gut flora and can cause cv symptoms with long term use
opioid receptors are present on immune cells therefor chronic use of opioids can cause
immunosuppression
abuse resistant opioids are formulated how
more difficult to ingest active ingredient by mixing opioid with antagonist
do opioid allergies really exist
usually just s/e of the medication; only 3 reported cases of true fentanyl allergy
3 mcg/kg fent 25-30 mins pre op will decrease MAC of des and iso by
50%
sufentanil decreases MAC with enflurane by
70-90%
alfentanil decreases MAC up to
70%
remi decreases AMC by
50-90%
when giving neuraxial opioids we target
opioid receptors in lamina II or the substantia gelatinosa
a neuraxial opioid is injected into the
epidural or sas
targeting neuraxial opioids will NOT cause
sympathectomy, sensory block, or weakness
epidural dosing is 5-10x more than
sas/intrathecal dose
when we give an epidural, the opioid
stays in the sas and must diffuse across the dura mater for systemic absorption
highly lipophilic fentanyl and sufentanil diffuse better in an epidural but morphine
has a longer duration
where do we want the epidural opioids to work/go
csf
places of epidural opioid uptake
epidural fat, epidural venous plexus, and diffusion across the dura
if the epidural opioid goes to the epidural venous plexus there will be systemic absorption; how can we counteract this?
epi
epidural fent peak
20 mins
epidural sufentanil peak
6 mins
if a drug is more cephalad it means that it is
more likely to travel up the spinal cord; more h2o soluble
fent and sufent are lipid soluble. _____ is less lipid soluble and more likely to hang out in the cns and go ______
cephalad
body position has little effect on whether or not a drug goes cephalad; these have more effect
coughing, blowing, straining
most common s/e of neuraxial opioids
pruritis, n/v, urinary retention, RD, sedation, CNS excitation, herpes simplex labialis, neonatal morbidity
