methadone C6 Flashcards
(18 cards)
how does opioid dependance occur
Opioid dependence occurs when repeated use of opioids causes changes in the brain’s reward, motivation, and pain systems. Over time, the brain adapts to the presence of the drug, leading to tolerance (needing more for the same effect) and physical dependence (experiencing withdrawal symptoms without it). Psychological dependence can also develop, where the user feels a strong urge to continue using the drug for its pleasurable effects or to avoid discomfort.
How does opioid tolerance occur
In the case of opioids, the brain reduces the number or sensitivity of opioid receptors after repeated exposure. As a result, the same dose produces less pain relief or euphoria, prompting the user to increase the dose, raising the risk of dependence and overdose.
MOA opioids
Binds to mu -opioid receptors in the CNS. Stops stimulation of ach release from presynaptic neurine that would activate muscarinic receptors on the postsynaptic membrane. This prevents the signal from being transmitted and therefore, depression of the pain response = analgesia.
Binding to GPCR (mu-opioid receptor) = GTPGDP = alpha and beta/gamma subunit dissociation = inhibit adenylyl cyclase = less cAMP
Also = promote K+ efflux = membrane hyperpolarisation = Ca2+ influx inhibited = inhibition on NT release = pain relief
counselling with opioids (excl methadone)
respiratory depression symptoms
OTC - 3 day use only (some preparations contain paracetamol/ibuprofen/aspirin so dont take anything else containing paracetamol)
can make you drowsy so take care when driving or operating machinery
when do people swicth from supervised to non supervosed methadone
once compliance is assured and the medical professional sees no risk of abuse or misuse
what is methadone
a long acting opioid mu receptor agonist
blocks opioid withdrawal for 24 hours
indicated for the treatment of opioid drug addictions
treatment regime for methadone
patinet started on a lower dose. titrated up - stabalised
max dose increase per week of 30mg
key risk with opioids and symptoms
respiratory depression
difficulty brething
unable to catch breath
SOB
immediate medical attention required
counselling when inititaing a ptinet on methadone
taken daily
supervised for at least 3 months
prolonged use of opiouds may lead to dependance and addiction. inc risk of adverse events such as respiratory depression
who can supervise someone taking methadone
how many days can be missed of a methadone prescription before reffering back to the GP and retitrating
2
if 3 or more consecutive days are missed contact prescriber - risk of loss of tolerance
why does methadone need to be titrated
risk of accumulation and toxicty if not adjusted properly
- long half life so drug can accumulate in the body
takes 4-10 days to reach steady state
look out for withdrawal - the dose may be too low to begin with and not the equivalent of the opioid the person was prev abusing
how does methadone differ from other opoids and what are the similarities
methadone as the same MOA but differes in terms of its pharmacokinetics: half life, time to reach steady state, bioavaliability, metabilism and the risks associated with it
cardiovascular risk associated with methadone
QT interval prolongation
ECG is required in patinets who have a history of cardiac abnormalities or if the patient is required to take over 100mg
can you dispense advanced methadone doses
yes
on a prior suitable day if the pharmacy is closed
must be dispensed in separate containers
difference between buprenorphine and methadone
buprenorphine is less sedating than methadone
if you suspect someone is abusing illegal opioids such as heroin, should we still administer their daily methadone
yes you should IN SOME CASES - however this is a case to case thing
prevent relapse and withdrawal
assess for intoxication
document your concerns
you can withold the dose temporarily and seek medical advice
asking the patient straight up might not be effective as they can lie but it is then important to tell them that there is a greater risk of harm if they are potentially abusing opiates and reciving methadone - also counteracts the purpose of methadone
higher dose = higher risk
always encourage honesty
