Opioids Flashcards
Define opium
Natural extract of the poopy papaver somniferum. It contains morphine and other related compounds.
Define opioid
Any substance that produces morphine like effect which are blocked by morphine antagonists
What are opioids?
Huge family of drugs which are administered for their analgesic action. There are weak and strong opioids. Weak opioids have a ceiling effect which is where escalation of the dose causes side effects without improving analgesia.
How do you convert oral morphine dose into each of the following;
- Oral oxycodone,
- Codeine,
- Tapentadol,
- Buprenorphine,
- Fentanyl patch,
- Tramadol,
- IV morphine
- Oral oxycodone ÷ 2 (mg)
- Codeine x 10 (mg)
- Tapentadol x3 (mg),
- Buprenorphine ÷ 2 (mcg/h),
- Fentanyl patch ÷ 4 (mcg/h),
- Tramadol x5/x10 (mg),
- IV morphine ÷ 3 (mg)
Name examples of strong opioids
- Morphine,
- Oxycodone,
- Diamorphine
- Fentanyl,
- Pethidine,
- Remifentanyl,
- Methodone
Name an example of a middle strength opioid
Tramadol (however proconvulsive drug so not to people with epilepsy!)
Name examples of weak opioids
Codeine and dihydrocodeine
Name opioid antagonist?
Naloxone (naltrexone which is used in recovery from addiction)
An antagonist is a drug with a high affinity for the receptor but no intrinsic activity
What is loperamide?
It is an opioid but it acts in the myenteric plexus and so is used to stop diarrhoea.
What are some routes of administration?
- Oral (best route in cancer pain)
- Transmucosal lozenges,
- Transdermal Patch
- IM injection
- IV infusion/injection
- Epidural
Why is the oral bioavailability not 100%?
The drug will be absorbed in the small intestine however not 100% will be absorbed, and then the drug that does get absorbed has to travel via the liver before it can reach the systemic circulation so is metabolised by the liver before it reaches systemic circulation (first pass metabolism) Oxycodone and tramadol have the best oral bioavailability
Name the opioid receptors
- Mu opioid peptide receptor (MOR)
- Kappa (KOR)
- Delta (DOR)
- Nociception (NOR)
Name a couple examples of endogenous opioids
Enkephalins and endorphins
What occurs at a cellular level following binding of an opioid to receptor?
Coupling with G proteins which causes potassium channels to open, allowing for potassium to move out of the cell causing it to hyperpolarise, calcium channels are shut which reduces release of NTs, as few calcium ions can enter the cell. Negative impact of conversion of AMP to cAMP which reduces NT release
What are the effects of opioids on the CNS
- Analgesia,
- Sedation,
- Euphoria (misuse and dependency issues),
- Respiratory Depression (main cause of death in opioid OD),
- Meiosis (MOP on edinger westphall nucleus)
