Opioid Pharmacotherapies Flashcards
(29 cards)
How do opioids produce reward?
By binding to GABAergic interneurons which release dopamine.
Results in euphoria and analgesia.
Why does the IV route have a greater euphoria effect that the oral route?
The faster the influx of drug into the blood, the greater the euphoria.
What are the 3 classes of opioids and give examples of each.
Natural opioids: morphine and codeine
Semi-synthetic opioids: heroin and oxycodone
Purely synthetic opioids: fentanyl, methadone and buprenorphine
Give examples of drugs that are controlled by the misuse of drugs act, 1971.
- diacetylmorphine (heroin)
- morphine
- fentanyl
Which opioid drugs do the BNF list?
- codeine phosphate
- morphine salts
- diamorphine hydrochloride
- dihydrocodeine tartrate
- oxycodone hydrochloride
- pavaveretum
- methadone
- buprenorphine
- fentanyl
Name the 7 properties of opioids
PREECAS
- CNS depressant
- pinned pupils
- respiratory depressant
- emesis
- euphoria
- analgesic
- sedation
Metabolic pathway for codeine
codeine —> norcodeine —> codeine glucuronide
Metabolic pathway for heroin
Diacetylmorphine —> 6-monoacetylmorphine
Metabolic pathway for morphine
morphine —> morphine-3-glucoronide + morphine- 6- glucoronide + normorphine —> normorphine glucuronide
Metabolic pathway for dihydrocodeine
codeine –> nordihydromorphine + nordihydrocodeine
Heroin: diacetylmorphine
- is a prodrug that is metabolised to its active metabolites in vivo- morphine and 6-monoacetylmorphine (6-MAM)
- so heroin itself does not bind to opiate receptors
- used by IV, skin popping, smoking, snorting or chasing
- tolerance and dependence
Why does heroin never appear in urine?
The drug has a half life of 3 minutes
Prodrug itself does not bring about its pharmaceutical effect
What is the half - life of morphine?
2-4 hours
Low bioavailability when given orally
short acting drug
Activity of morphine-3-glucuronide and morphine- 6 glucuronide?
morphine-3- glucuronide has no analgesic activity
morphine-6 glucuronide is able to penetrate the BBB and is pharmacologically active
When is morphine clearance decreased and analgesic effects increased ?
in elderly patients who have decreased renal function
What is the half life of methadone?
24 hours
orally effective
Effects of methadone
- constipation
- sweating
- respiratory depression
In what condition is the excretion of methadone much slower?
in chronic severe liver disease/ liver cirrhosis
- not viral hepatitis
Therefore, give lower doses for patients commencing methadone with liver cirrhosis
Dose of methadone in acute viral hepatitis?
Dosing as normal
When may clearance of methadone slow down?
- in chronic active hepatitis
- obstructive jaundice
Buprenorphine
- synthetic opioid
- partial agonsit at the mu receptor
- quick onset of action 30-60 minutes
- peak effects 1-4 hours
- high first pass metabolism so often prescribed sublingually
- available in 0.4, 2 and 8mg sublingual tablets
- standard therapeutic dose: 8mg-24mg per day SUBUTEX
- IV, IM or SC injection: TEMGESIC 0.3mg in 1 ampolues
Half- life of buprenorphine?
5 hours
Fentanyl
- drug metabolised to norfentanyl within 72 hours after iV dose
- 75% dose is excreted in the urine
what is the mean elimination half life or fentanyl IV, transdermal patches and lozenges?
IV: 2 to 4 hours
transdermal patch: 17 hours
lozenge: 7 hours
