Pain and analgesics 3 (analgesic drugs) Flashcards
What general process is boosted by analgesic drugs?
Descending inhibition of nociception
Which processes are inhibited by analgesic drugs?
Central sensitisation and peripheral sensitisation
How do nonsteroidal anti-inflammatories cause analgesia?
They inhibit the process of peripheral sensitisation
How do opioid analgesics cause analgesia?
Boost the descending inhibition of nociception
What do opioids mimic in order to have their analgesic effect?
Endogenous opioid agonists
Where do opioids act?
On opioid receptors
Examples of opioids?
Morphine, heroin, fentanyl, codeine
What are some low potency opioids?
Codeine, pethidine, buprenorphine
What is etorphine used for?
Veterinary medicine–> large animals
What is naloxone?
An opioid receptor antagonist
How does naloxone work?
It is a opioid mew delta and kappa antagonist
Which drugs are used for mild pain?
NSAIDs (nonsteroidal anti inflammatories)
Examples of NSAIDs?
Aspirin, ibuprofen
What are opioids given to people in moderate pain?
Codeine, buprenorphine
What are some opioids given to people in severe pain?
Morphine, fentanyl
How do the opioid receptors on free nerve endings have an inhibitory effect?
When an agonist binds K+ channels open and allow K+ to leave the cell–> hyperpolarisation
Where are supraspinal opioid receptors?
PAG and locus coeruleus
Which type of opioid receptor do most analgesics target?
Mu
Which opioid receptor do morphine, methadone and fentanyl target?
Mu
Can morphine and fentanyl also target delta and kappa receptors?
Yes
Main issue with mu opioid receptors?
When agonised they can cause respiratory depression
Benefit of targeting delta and kappa receptors over mu?
They do not cause respiratory depression when agonsied
Mood effect of mu receptor being agonised?
Euphoria
Mood effect of kappa receptor being agonised?
dysphoria
Effect of kappa receptors being agonised on bodily waste?
Diuresis
Mood effect of delta receptor being agonised?
none
Main issue with agonising delta opioid receptors?
Proconvulsant
Undesirable effects of mu opioid receptor?
Constipation, sedation, nausea and vomiting, itching
Why does mu opioid receptor agonists being activated cause constipation?
They activate mu opioid receptors in the gut
Why can methylnaltrexone be taken to prevent constipation but not the analgesic effect of opioids targeting mu receptors?
It cant cross the blood brain barrier meaning it can block the opioid receptors in the gut (so no constipation) but cant access the locus coeruleus or PAG
What is psychological dependance?
Addiction
What is physical dependance?
When someone stops taking a drug and they have physical withdrawal symptoms
Result of increasing potency of mu receptor agonist on side effects?
They increase
What changes need to be made to the dose of a drug if continued use occurs?
The dosage will need to increase
What is the main active ingredient in an opium poppy?
morphine
Main structural difference between morphine and heroin?
Heroin has two acetyl groups where morphine has two OH groups
What benefit does having two acetyl groups instead of two OH groups give heroin over morphine?
It crosses the blood brain barrier more easily
What drawback is there of having two acetyl groups instead of two OH in heroin compared to morphine?
Makes heroin completely ineffective against the mu opioid receptor (heroin itself is not an opioid receptor agonist)
Why does heroin not having the correct structure to be a mu opioid receptor agonist not really matter?
There are many enzymes in the brain which can cleave the acetyl groups off
What is a pro-drug?
A drug that has to be metabolised in order to be its active ingredient
Which analgesics are taken in pill form?
Morphine, codeine
Which analgesics are taken via intravenous injections?
morphine, diamorphine, fentalyl
