Pharmacology Flashcards
mechanism of methadone
FULL AGONIST of mu opioid receptor
duration of action methadone
long acting (half-life 15-60 hours)
affinity of methadone at opioid receptor?
weak (can be displaced by partial agonists or antagonists like buprenorphine or naltrexone respectively)…CAN PRECIPIATE WITHDRAWAL if this happens
harmful side effects of methadone (2)
- respiratory suppression
- qt prolongation
monitor closely to prevent overdose
methadone metabolism
- CYP3A4
- mostly metabolized by liver but small proportion can be found in urine (AND THEREFORE IN UDS)
buprenorphine metabolism
liver
CYP3A4
small excreition in urine so CAN be detectable in UDS (but sometimes need to be a send out or confirmatory test because it may not always show up)
active metabolite of buprenorphine and what is it’s clinical significance?
norbuprenorphine
sometimes you can get levels of buprenorphine and norbuprenorphine in UDS to assess how patient is taking their med; patients may tamper with urine and add a little buprenorphine but they will show low norbuprenorphine levels if they haven’t actually been taking the med
best admin route for buprenorphine
NOT SWALLOWED (poor first pass metabolism) can use other formulations like sublingual/subdermal implant/depot/tablets to help this
mechanism buprehnorphine
PARTIAL agonist at mu receptor
risk for respiratory suppression on buprenorphine
VERY LOW
duration of action buprenorphine
long acting, half life (24-36 hours)
and slow dissociation from receptor
affinity buprenorphine to opioid receptor
HIGH; can displace other opioids
ex: if you use heroin while on buprenorphine, you won’t get euphoric (buprenorphine displaces heroin)
So what are the benefits of using buprenorphine?
- prevents withdrawal symptoms
- decreases cravings
- decreases effects of other opioids
Effectiveness of transdermal (patch) and IV buprenorphine
they have been approved for analgesia/pain; BUT NOT APPROVED for treatment of opioid use disorder
What is the advantage of prescribing buprenorphine+naloxone (suboxone)?
developed to DECREASE IV/injectionDRUG USE
- less likely to be diverted
- less euphoria
encouraged to use combo product
biochemical mechanism naltrexone
opioid receptor ANTAGONIST
(blocks receptor from action of other opioid…also has high affinity to receptor)
BUT CAN PRECIPIATE WITHDRAWAL so taper off or make sure patient is off opioids for several days before starting
disadvantage of naltrexone tablet?
poor compliance
DO THE INJECTABLE
which kind of patients would naltrexone be good for?
patients who prefer not to be on any opioids
behavioral mechanism of naltrexone
blockade of reinforcing effects of heroin leads to gradual extinction of drug seeking/craving
people who use opioids on naltrexone experience no effect of expogenous opioids and often stop using them
pharmacological mechanism of naltrexone
decreases reactivity to drug-conditioned cues and decreases craving (i.e blocks endorphins) which minimizes pathological responses contributing to relapse
disadvantage for buprenorphine
concern for diversion (so use combo meds like suboxone, they’re less likely to get diverted)
what to consider if patient decides to halt naltrexone treatment?
if they use again, they may use the same amount they did before they stopped…despite their lower tolerance…which will put them at risk for OVERDOSE
benefits of methadone
RETENTION IN TREATMENT (dose dependent)
how long patients decide to stay in treatment and longer abstinence
treatment dosing buprenorphine
dose dependent rise so start at like 8 ish mg then get stable…if persistent cravings can go up to 16
