7.2 Opiods Flashcards
How do opiods work?
They prevent the release of substance P in Periphery
and are psychoactive on the CNS
Examples of opiods?
Morphine, Oramorph
Codeine
Methadone
What are some endogenous opiods?
Their precursors?
Enkephalins - Proenkephalin
Endorphins - POMC
Dynorphins - Prodynorphins
What receptors do opiods act on?
Mew
Delta
Kappa
What is the main opiod receptor?
Mew
What does the Mew Opioid Receptor do?
Location?
Mostly in Periaqueductal Grey (supraspinal) and cortex
Analgesic
It activates K+ channels to hyperpolarise synapses, prevent pain signals from being transmitted/raises threshold
MAIN EFFECTOR OF OPIODS, Morphine
What does the Delta Opioid Receptor do?
Location?
Widely distributed
Decreases cAMP, so fewer NT released
What does the Kappa Opioid Receptor do?
Location?
In Spinal cord
Inhibits Ca2+ channels
What are the ADRs of M and D Opioid receptors?
Dependence
Respiratory Depression
What is the Main ADR of Kappa Receptors?
Confusion (Dysphoria)
What are some ADRs of Mew Receptors?
Resp Depression Hypotension (vasodilation) Dependence Tolerence Nausea and Vomiting (acts on vomiting centre of brain) Miosis Drowsiness Constipation (inhibits gut nerve transmission)
What are some Opioid Agonists?
Morphine
Codeine
Methadone
What are some Opioid Antagonists?
Naloxone
How is Morphine metabolised?
Straight to Phase 2 glucoronidation
Creates active metabolite (M6G) and M3G
Has long half life due to active metabolite
What are the properties of morphine?
Half life?
Bioavailability?
Poor lipid solubility –> poor oral bioavailability
Long half life due to active metabolite
What is Diamorphine?
Heroin!
More lipid soluble (has acetyl group) so crosses BBB
Short half life but converted into morphine
Good way to quickly get analgesia to CNS
What is Codeine?
Given?
Bioavailability?
Mild analgesic
50% oral bioavailability
Prodrug to morphine, converted by P450 enzyme (some lack!!!)
When do we use Opioid Agonists?
Anasthesia - fentanyls
Dependence - methadone
Analgesia- good for visceral, moderate pain, pallative care
Diarrhoea - morphine+clay
What might you use in pregnancy?
Why is it a bit sketchy?
Labour Pain - Pethidine
But it is potent, can cause convulsions, no repeat doses, seems silly….
When do we use opioid antagonists?
Examples?
To treat an overdose or dependence
Prevents respiratory depression
Naloxone (IV) Naltrexone
Opioids are controlled drugs, what does this mean?
Must put your name and address on it, sign, date. Must write in figures and letters the form and dose given
When might you use an opioid antagonist/agonist?
Analgesia without euphoria (antagonises Mew)
Nalbuphine
What is NOP?
New endogenous receptor
Has nociceptin which binds to trasmit pain
What is NOP?
New endogenous receptor
Has nociceptin which binds to transmit pain
