Pharmacology (Analgesics) Flashcards by Emma Feechan

ways analgesics can reduce nociception and pain

decrease nociceptor sensitisation by blocking prostaglandins (NSAIDs)
suppressing nerve conduction at Na+ channels (lidocaine)
suppressing synaptic transmission in dorsal horn (opioids)
activating descending inhibition
targeting ion channels upregulated

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analgesic rungs

3/ strong opioid
2/ weak opioid
1/ NSAIDs or paracetamol

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examples of strong opioids

morphine
heroin
fentanyl
oxycodone
hydromorphone

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examples of weak opioids

codeine
tramadol
dextropropoxyphene

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important brainstem regions in pain

periaqueductal grey (midbrain)
locus coeruleus (pons)
nucelus raphe magnus (medulla)

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what does excitation of PAG cause?

profound analgesia

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what does NRM cause when activated by PAG?

suppression of nociceptive transmission

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what does the LC do?

projects to dorsal horn and are excited inhibiting nociceptive transmission

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what receptor do opioids act on?

GPCR

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what do opioids do when they bind to GPCR?

inhibit Ca2+ channels (suppressing neurotransmission of nociception) and open K+ (suppress excitation post-synaptically)

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adverse of opioids

addictive potential
apnoea
orthostatic hypotension
action on CTZ causing N&V
confusion, euphoria, hallucinations

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how do opioids cause apnoea?

blunts medulla respiratory centre to CO2 causing hypercapnia responses

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how do opioids cause orthostatic hypotension?

reduce sympathetic tone and bradycardia with mast cell degranulation

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what do opioid agonists act on?

u-opioid receptors

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opioid agonists

morphine
diamorphine
codeine
fentanyl
pethidine
buprenorphine
tramadol
methadone

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what organ metabolises morphine?

liver

what organ excretes morphine?

kidney

what is diamorphine?

a more lipophilic version of morphine so ha rapid onset

additional properties of codeine?

anti-diarrhoeal

antitussive

higher potency derivatives of codeine

oxycodone

hydrocodone

when is pethidine used?

acute pain, particularly labour

what is buprenorphine used in?

chronic pain with patient-controlled injections

when should you avoid tramadol?

epilepsy

what can methadone be used in?

withdrawal from strong opioids such as heroin

opioid antagonists

naloxone naltrexone alvimopan and methylnaltrexone

when is naloxone used?

reverse opioid toxicity associated with overdose can trigger acute withdrawal episode may be given to new-borns with opioid toxicity as a result of administration of pethidine during labour

properties of NSAIDs

analgesic antipyretic anti-inflammatory

action of NSAIDs

inhibit prostaglandins COX1 and COX2 suppress sensitisation of nociceptors by prostaglandins decrease recruitment of leucocytes suppression in dorsal horn

adverse of NSAIDs

GI damage

conditions with neuropathic pain

trigeminal neuralgia diabetic neuropathy post-hepatic neuralgia phantom limb pain

management options for neuropathic pain

gabapentin and pregabalin amitriptyline carbamazepine

action of gabapentin and pregabalin

reduce expression of Ca2+ channels which causes a decrease in neurotransmitters (glutamate and substance P)

what neuropathic pain condition is gabapentin used in?

migraine prophylaxis

what neuropathic pain condition is pregabalin used in?

painful diabetic neuropathy

action of amitriptyline

act centrally by decreasing reuptake of NA

action of carbamazepine

block Na+ channels

what neuropathic pain condition is carbamazepine used in?

trigeminal neuralgia