Week 6- sbstance misuse Flashcards
(33 cards)
what are some full agonists opioids?
Full agonists ▪ -Codeine ▪ -Diamorphine (Heroin) ▪ -Fentanyl ▪ -Methadone ▪ -Morphine ▪ -Pethidine
what are some partial agonists?
▪ Buprenorphine
Subutex®
what are some antagonists?
Antagonists ▪ Naloxone (Injection) – Narcan® ▪ Naltrexone (tablets) ▪ Nalmefene- (alcohol)
why use methadone or buprenorphine?
-long lasting
-once daily BOTH
formulations not easily inject-able
-historical unpleasant formulation
what are the effects of methadone on the CNS?
▪ Euphoria- not as pronounced as heroin ▪ Pleasant, warm feeling in the stomach ▪ Pain relief ▪ Drowsiness- not when tolerant ▪ Nausea/vomiting- stimulation of chemoreceptor trigger zone ▪ Respiratory depression ▪ Cough reflex depression ▪ Arms & legs feel heavy- ?increased blood flow to periphery
what are the effects on the peripheral NS?
▪ Dryness of the mouth, eyes, nose- reduction of secretion of
saliva tears & mucous
▪ 53% methadone users report dental problems
(methadone is acidic in nature)
▪ Constipation- opiates are good at slowing passage of food
(patients require high fibre & high fluid)
▪ Constricted pupils- reliable indicator of the level of opiates in
blood stream
what are some histaminergic effects of methadone?
▪ Itching ▪ Sweating ▪ Blushing ▪ Flushing ▪ Constricting of the airways
what are some other effects of methadone?
▪ Reduced or absent menstrual cycle- may still become pregnant ▪ Sexual dysfunction ▪ Hallucinations ▪ Heart pounding transient effect
how is methadone metabolised?
• Methadone is soluble in lipids • Extensive metabolism in the liver • Binds to albumin • Slow transfer between tissues • Half life single dose 15 hours • At steady state the half life has a mean of 25 hours (once daily dosing) Missed dose: after 25 hours, level drops to about half the peak level and after 48 hours drops to 25% peak level
what is the tolerance of methadone?
▪ Tolerance to opiates rises more quickly during second &
subsequent exposures to the drug
▪ Tolerance to miosis and constipation develops very slowly and
both are often present years after treatment
▪ Tolerance may go as quickly as it develops
Overdose risk for people
post detoxification and
intermittent users
particularly prisoners
released
what is the effectiveness of methadone and buprenorphine?
• Both are effective & used in the
treatment of opioid
dependence & detoxification
what is the maintenance of methadone and buprenorphine?
• Methadone is considered the
gold standard 60-120mg
• Buprenorphine 12-32mg
what assessment is needed for methadone and buprenorphine?
• Dependence confirmed by
history & examination. Urine or
oral toxicology screening
what are some safety consideration of methadone?
• Low opioid tolerance
• Avoid additional drugs which may cause respiratory
depression such as benzodiazepines (be aware of self
med with alcohol)
• Avoid high initial dose (40mg may be fatal in an adult, 10mg in
children)
• Avoid rapid dose increases - methadone slow to clear
• Minimise side effects of constipation and sweating
• Potential interactions QT over 100mg/cardiac risk
• Minimise diversion, accidental ingestion and
overdose errors
how is methadone induction occurring dose wise?
-The first dose should not exceed
40mg. If uncertain then 10-20mg
-Where doses need to be increased
the increment should be no more
than 5-10mg in one day
-The total weekly increase should
not usually exceed 30mg above the
starting day’s dose
• Methadone-related deaths during MMT occur during the first
10 days of treatment and are more common with higher
induction doses
• There is no way of directly measuring tolerance to
methadone.
• Estimate of opioid tolerance is based on history and physical,
supported by toxicology tests.
what is the buprenorphine induction occurring dose wise?
Dose induction with buprenorphine may be carried out more rapidly
with less risk of overdose
▪ Timing is crucial
Buprenorphine can cause precipitated withdrawals when
transferring from heroin or other opioids.
▪ Start at least 8-12 hours post heroin, 24-36 hours post
methadone, 4mg is a good starting dose then escalate the dose
quickly
▪ Doses above 12mg block the effect of heroin and other opiates
on top
what are the advantages of methadone?
▪ Established and familiar ▪ Good evidence base for Methadone maintenance treatment ▪ Trusted ▪ Sedating ▪ Cheap ▪ Full agonist ▪ Variety routes/forms ▪ 1 st choice in pregnancyalthough evidence points the other way?? ▪ Easier to supervise
what is the advantages of buprenorphine?
▪ More difficult to use on top (maintenance minimises drug seeking behaviour, -ve reinforcement) ▪ Good for clients at risk of overdosing ▪ Safer in overdose ▪ Less stigmatised ▪ Easier to detox from, easier switch to naltrexone ▪ Less sedating ▪ Better outcomes of newborns ▪ Can’t be adulterated ▪ Initial titration rapid
what is the disadvantages of methadone?
▪ Easy to overdose ▪ Can use heroin on top ▪ Leakage onto the streets (adulterated, injected) ▪ Stigmatised drug (older users, deters new clients) ▪ Rots teeth?? ▪ Stored in fatty tissue ▪ 3 days to steady state ▪ Long detoxification ▪ Avoids withdrawals but doesn’t stop craving ▪ Sedating
what is the disadvantages of buprenorphine?
▪ Expensive ▪ More difficult to supervise (concealment) ▪ Poorer evidence base/less experience ▪ Can be injected ▪ Unpleasant taste (S/L) ▪ Only one dosage form ▪ Less sedating ▪ Precipitated withdrawals
what does NICE say?
-Higher fixed doses of methadone maintenance treatment (MMT) are more effective than lower fixed doses -MMT reduces mortality, HIV risky behaviour and levels of crime c/w no therapy -Fixed dose MMT has higher levels of retention in treatment & lower rates of illicit opioid use c/w placebo or no treatment
what is the role of noradrenaline?
▪ The Locus Coeruleus (LC) is central to the symptoms
of opiate withdrawal. It produces 70% of brain
noradrenaline
▪ LC develops tolerance to opiates, abrupt cessation of
opiates then leads to enhanced LC activity with an
increase in NA release & turnover. This
‘noradrenaline storm’ leads to opiate withdrawals.
These withdrawals can be measured using subjective
and objective opiate withdrawal scales.
how to remain free of opioids?
Naltrexone
• Competitive opioid antagonist with high affinity
• Blocks the euphoric and other effects of opioids and thereby
minimising the positive rewards associated with their use
• Is licensed for use as an adjunctive prophylactic treatment for
detoxified formerly opioid-dependent people
• Must be prescribed within a package of support including
relapse prevention
• Clients may be at risk of a fatal overdose caused by
respiratory depression if they relapse while taking
naltrexone.
what should be done before using naloxone?
Administration of naltrexone must not be started before a naloxone
challenge test is performed and a negative result obtained.
• Naloxone test
• Subcutaneous: Administer 0.8 mg naloxone subcutaneously.
Observe the patient for 20 minutes for signs and symptoms of
withdrawal
• Confirmation of the test: If there is any doubt that the patient
is opioid-free, treatment with naltrexone should be delayed 24
hours. In this case, the test should be repeated with 1.6 mg
naloxone
• If there is no evidence of a reaction, naltrexone administration
may be initiated with 25 mg by mouth.
