Opioids Flashcards
Define pain. (3)
A complex, unpleasant awareness of sensation modified by the brain and affected by experience, expectation, context and culture.
Define nociception (2)
A non-conscious reflex prompted by trauma to tissue.
Describe the path that pain takes from the tissue to the brain. (9)
Nociceptors stimulated, releasing substance P and Glutamate
Afferent nerves stimulated (A(delta) fibres for sharp, C fibres for dull)
Spinothalamic tract followed, so fibres deccusate
Action potential ascends and synapses in the thalamus
Projects to the post-central (sensory) gyrus.
Describe how we peripherally modulate pain. (5)
“Rubbing it better” prompts the inhibition of the A(delta) and C fibres in the substantia gelatinosa through A(beta) fibres. This reduces the pain signals transmitted to the thalamus.
Describe how we centrally modulate pain. (2)
Periaqueductal grey matter (nose and mouth of Mickey Mouse in the brainstem).
Name three types of endogenous opioids. (3)
Encephalins
Dynorphins
Beta-endorphins
Describe the receptors that endogenous opioids act on. (4)
All GPCRs
Encephalins - DOP (delta)
Dynorphins - KOP (kappa)
Beta-endorphins - MOP (mew)
Describe the distribution of the receptors that endogenous opioids act on. (3)
Encephalins - widely distributed
Dynorphins - spinal cord / brain.
Beta-endorphins - GI tract
Describe what stimulating the receptors of endogenous opioids leads to. (2)
All leads to a decrease in cAMP release.
Describe the result of the stimulation of receptors for endogenous opioids. (3)
Encephalins - influx of calcium
Dynorphins - influx of calcium, efflux of potassium.
Beta-endorphins - efflux of potassium
Describe what the movement of ions prompted by endogenous opioids causes. (3)
Hyperpolarisation and decreased substance P release, to decrease nociceptor response.
Describe what each effect endogenous opioid has on the body. (12)
Encephalins - analgesia, dopamine inhibition, modulating mew receptors.
Dynorphins - analgesia, dysphoria, diuresis
Beta-endorphins - analgesia, dependence, euphoria, respiratory sedation, depression.
Describe the WHO analgesia ladder for chronic use of painkillers. (5)
Simple analgesia eg NSAIDs / paracetamol.
Weak opioid eg codeine
Strong opioid eg morphine / fentanyl
Describe the MoA and aims of opioid therapy. (4)
Exploit the natural mew receptors through agonism or antagonism.
Aim is to modulate pain, but also used in cough, diarrhoea, and palliation.
Name 6 strong agonists of the mew receptors. (6)
Morphine Fentanyl Heroin (diamorphine) Methadone Oxycodone Oxymorphone
Name one moderate agonist of the mew receptor. (1)
Codeine
Name one mixed agonist / antagonist of the mew receptor (1)
Buprenorphine
Name two antagonists of the mew receptor (2)
Naloxone
Naltrexone
Name one opioid that does not agonise or antagonise the mew receptor. (1)
Tramadol.