Physiological analgesia and analgesic drugs Flashcards
What are opiates?
Substances extracted from opium (or similar structures)
What are opioids?
Any agent that act upon opioid receptors
What are the 5 ways that analgesia may reduce nocioception and pain?
1- Acting at the site of injury (decrease nociceptor sensitisation in inflammation)- e.g. NSAIDS
2-Blocking nerve conduction e.g. local anaesthetics
3-Suppressing transmission of nociceptive signals in the dorsal horn of the signal cord e.g. opioids, some anti-depressants
4-Activating (or potentiating) descending inhibitory controls e.g. opioids
5- Target ion channels unregulated in nerve damage e.g. antiepileptics
Perception of pain is highly variable, for the same degree of nociceptive activity, depending on the level on concurrent innocuous sensory input and behavioural context more or less pain may be perceived
Thanks for turning this card over Because it wasn't a question really was it? Well it's true anyway Go get a snack and rehydrate Keep going
Pain can be reduced by simultaneous excitation of low threshold mechanoreceptors. What type of fibres are these?
LTMs
Ab-fibres
TRUE/FALSE
All sensory afferents are inhibitory
FALSE
they are all excitatory
When the periaqueductal grey (PAG) is excited what happens?
Descending inhibition of nociceptive transmission in the dorsal horn of the spinal cord
What is opiod action mediated by?
G protein coupled opiod receptors
What opiod receptors are responsible for the analgesic actions of opioids?
u
What opiod receptors contribute to analgesia but activation can be proconvulsant?
d
What opiod receptor continbcute to analgesia at the spinal and peripheral level and activation is associated with sedation, dysphoria and hallucinations
K
What are the major adverse effects of opioids?
Apnoea
Orthostatic hypotension
Nausea, Vomiting, Constipation, increased intrabiliary pressure
Confusion, euphoria, dysphoria, hallucinations, dizziness, myoclonus, hyperalgesia (with excessive use)
What is the mechanism by which opioids trigger bronchospasm in asthmatics?
Mast cell degranulation.
Are most opioids agonists or antagonists?
Most are agonists
the ones that are antagonists are naloxone, naltrexone, alvimopan and methylnaltrexone
What is morphine metabolised by?
Liver
Heroin is more lipophilic than morphine TRUE/FALSE
TRUE
Why should pethidine not be used in conjunction with MAO inhibitors?
Excitement
Convulsions
Hyperthermia
TRUE/FALSE Tramadol is a weak u-receptor agonist
TRUE
What is used to assist with withdrawal from strong opioids?
Methodone
What is used to reverse opiod toxicity?
Naloxone
What opiod drug is sometimes used in labour?
Pethidine
NSAIDs reduce nocioceptor sensitisation TRUE/FALSE
TRUE
What is the difference between COX 1 and COX 2?
COX-1 is constitutively active
COX-2 is induced locally at sites of inflammation
What do COX do?
Suppress the decrease in activation threshold
Decrease recruitment of leukocytes that produce the inflammatory mediators
Suppress the production of pain-producing prostaglandins
Why is paracetamol not classed as an NSAID?
Lack anti-inflammatory activity and acts only centrally
Why are selective COX-2 inhibitors not used?
They are prothrombotic
Name 4 conditions where neuropathic pain occurs
Trigeminal neuralgia
Diabetic neuropathy
Post-herpetic neuralgia
Phantom limb pain
Which opiod is used in migraine prophylaxis?
Gabapentin
Which opiod is used in painful diabetic neuropathy?
Pregabalin
How does amitriptyline work?
Acts centrally by decreasing the reuptake of noradrenaline and serotonin
How does duloxetine work?
Decreased reuptake of noradrenaline and serotonin
