26 Analgesic drugs Flashcards by Emma :)

26.01 OPIOID DRUGS

Opioid agonists: morphine, diamorphine (heroin), buprenorphine, codeine, oxycodone - actions

analgesia
sedation
euphoria/reduced anxiety
physical/psychological dependence
cough suppression and respiratory depression
inhibition of gut motility

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26.01 OPIOID DRUGS

Opioid agonists: morphine, diamorphine (heroin), buprenorphine, codeine, oxycodone - MOA

activates µ opioid receptors in the brain and spinal cord to inhibit pain transmission and modify the central perception of pain
activation of κ receptors may exert an additional effect on pain transmission in the spinal cord
may inhibit the activation of sensory nerve endings
opioid receptors are G protein–coupled receptors, which inhibit adenylate cyclase activity, open K+ channels and inhibit the opening of Ca2+ channels in nerve endings

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26.01 OPIOID DRUGS

Opioid agonists: morphine, diamorphine (heroin), buprenorphine, codeine, oxycodone - abs/distrib/elim

given orally or by SC/IM injection
glucuronic acid conjugation in the liver
half-lives: morphine 3-4h, buprenorphine 12h
the actions of diamorphine and codeine are due, at least in part, to metabolism to morphine

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26.01 OPIOID DRUGS

Opioid agonists: morphine, diamorphine (heroin), buprenorphine, codeine, oxycodone - clinical use

moderate to severe chronic and postoperative pain (codeine for mild pain)
epidural anaesthesia
neuropathic pain
treatment of painful cough
diarrhoea

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26.01 OPIOID DRUGS

Opioid agonists: morphine, diamorphine (heroin), buprenorphine, codeine, oxycodone - adverse effects

hypotension
constipation, nausea, vomiting, drowsiness, dizziness tolerance, dependence and withdrawal effects
larger doses - coma with respiratory depression

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26.01 OPIOID DRUGS

Opioid agonists: morphine, diamorphine (heroin), buprenorphine, codeine, oxycodone - special notes

naloxone is an opioid receptor antagonist at µ, δ and κ receptors and given in opioid overdoses
can cause withdrawal symptoms in opioid addicts

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26.02 OPIOID DRUGS

Synthetic analogues: pethidine, fentanyl, remifentanil, sufentanil - actions

analgesia
euphoria
physical/psychological dependence
respiratory depression
inhibition of gut motility
(antimuscarinic effects of pethidine cause tachycardia)

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26.02 OPIOID DRUGS

Synthetic analogues: pethidine, fentanyl, remifentanil, sufentanil - MOA

activates µ opioid receptors in the brain and spinal cord to inhibit pain transmission
activation of κ receptors may exert an additional effect on pain transmission in the spinal cord
may inhibit the activation of sensory nerve endings

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26.02 OPIOID DRUGS

Synthetic analogues: pethidine, fentanyl, remifentanil, sufentanil - abs/distrib/elim

given orally or IM
pethidine is subject to hydrolysis and P450 oxidation, half-life 3-5h
fentanyl is also available as a transdermal patch for long-term effects
remifentanil has a very short half-life (0.1h)

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26.02 OPIOID DRUGS

Synthetic analogues: pethidine, fentanyl, remifentanil, sufentanil - clinical use

moderate to severe pain
pethidine does not reduce uterine contractions so favoured for labour pain
remifentanil and sufentanil are given IV for surgical analgesia

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26.02 OPIOID DRUGS

Synthetic analogues: pethidine, fentanyl, remifentanil, sufentanil - adverse effects

constipation (less than morphine), nausea, vomiting, drowsiness, dizziness, tolerance, dependence and withdrawal effects
larger doses - coma with respiratory depression

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26.03 OPIOID DRUGS

Long-acting µ opioid receptor agonist: methadone - actions

analgesia
euphoria
physical/psychological dependence
respiratory depression
inhibition of gut motility

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26.03 OPIOID DRUGS

Long-acting µ opioid receptor agonist: methadone - MOA

activates µ opioid receptors in the brain and spinal cord to inhibit pain transmission and modify the central perception of pain
may inhibit the activation of sensory nerve endings

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26.03 OPIOID DRUGS

Long-acting µ opioid receptor agonist: methadone - abs/distrib/elim

oral absorption
long duration of action
P450 metabolism in liver
half-life 15-40h

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26.03 OPIOID DRUGS

Long-acting µ opioid receptor agonist: methadone - clinical use

analgesia
maintenance of opioid addicts and assistance in withdrawal program

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26.03 OPIOID DRUGS

Long-acting µ opioid receptor agonist: methadone - adverse effects

constipation, nausea, vomiting, drowsiness, dizziness
tolerance, dependence and withdrawal effects
larger doses - coma with respiratory depression and possible cardiac dysrhythmia

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26.04 OPIOID DRUGS

Atypical narcotic analgesic: tramadol, tapentadol - actions

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analgesia

26.04 OPIOID DRUGS

Atypical narcotic analgesic: tramadol, tapentadol - MOA

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weak agonist action at µ opioid receptors
main action: inhibits 5-HT and NA reuptake into nerve endings, so potentiates monoamine neurotransmission
analgesic action is inhibited by 5-HT3 receptor antagonists

26.04 OPIOID DRUGS

Atypical narcotic analgesic: tramadol, tapentadol - abs/distrib/elim

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given orally
subject to hepatic demethylation and conjugation
tramadol half-life 6h

26.04 OPIOID DRUGS

Atypical narcotic analgesic: tramadol, tapentadol - clinical use

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moderate/moderately severe pain
used postoperatively
neuropathic pain

26.04 OPIOID DRUGS

Atypical narcotic analgesic: tramadol, tapentadol - adverse effects

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dizziness, nausea and vomiting
respiratory depression, constipation and addiction (but less than with morphine)
convulsions

26.05 DRUGS USED FOR NEUROPATHIC PAIN

Tricyclic antidepressants: amitriptyline, nortriptyline, desipramine - actions

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reduction of neuropathic pain

26.05 DRUGS USED FOR NEUROPATHIC PAIN

Tricyclic antidepressants: amitriptyline, nortriptyline, desipramine - MOA

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analgesic action of antidepressants is mainly due to inhibition of the opening of neuronal voltage-gated Na+ channels (Nav 1.7 subtype), rather than to inhibition of monoamine reuptake
Na+ channel block reduces pain transmission from the site of nerve injury

26.05 DRUGS USED FOR NEUROPATHIC PAIN

Tricyclic antidepressants: amitriptyline, nortriptyline, desipramine - abs/distrib/elim

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given orally
hepatic P450 metabolism (nortriptyline is a metabolite of amitriptyline)
amitriptyline half-life 12-24h

26.05 DRUGS USED FOR NEUROPATHIC PAIN Tricyclic antidepressants: amitriptyline, nortriptyline, desipramine - clinical use

postherpetic neuralgia, diabetic peripheral neuropathy, neuropathic cancer pain pain treatment typically requires lower doses than depression treatment

26.05 DRUGS USED FOR NEUROPATHIC PAIN Tricyclic antidepressants: amitriptyline, nortriptyline, desipramine - adverse effects

sedation (antihistamine action, less with nortriptyline) blurred vision, dry mouth, constipation, urinary retention (antimuscarinic action) postural hypotension (α1-adrenoceptor antagonism) overdose potentially fatal due to cardiac dysrhythmia, severe hypotension, seizure and CNS depression

26.06 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: gabapentin, pregabalin - actions

reduction of neuropathic pain

26.06 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: gabapentin, pregabalin - MOA

effectiveness in neuropathic pain is due to binding to the α2-δ-1 and α2-δ-2 subunits of voltage-activated Ca2+ channels (P/Q or N-type) to block Ca2+ entry and exocytosis of transmitter (glutamate) from pain nerve endings

26.06 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: gabapentin, pregabalin - abs/distrib/elim

given orally excreted unchanged gabapentin half-life 6h

26.06 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: gabapentin, pregabalin - clinical use

postherpetic and trigeminal neuralgia pregabalin is also used for painful diabetic peripheral neuropathy

26.06 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: gabapentin, pregabalin - adverse effects

sedation, dizziness and unsteadiness

26.07 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: carbamazepine - actions

reduction of neuropathic pain

26.07 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: carbamazepine - MOA

inhibits the opening of neuronal voltage-gated Na+ channels to reduce nociceptive transmission from site of nerve injury

26.07 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: carbamazepine - abs/distrib/elim

given orally active P450 metabolite

26.07 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: carbamazepine - clinical use

second- or third-line treatment of neuropathic pain main uses: trigeminal neuralgia, diabetic neuropathy

26.07 DRUGS USED FOR NEUROPATHIC PAIN Antiepileptic drugs: carbamazepine - adverse effects

drowsiness, headache, mental disorientation, motor disturbances rare, but serious, adverse effects are liver damage, agranulocytosis and aplastic anaemia serious dermatological reaction in genetically susceptible patients strong inducer of cytochrome P450 enzymes, leading to many drug interactions

26.08 OTHER ANALGESIC DRUGS NSAIDs

ibuprofen, naproxen - COX inhibitors mild to moderate pain due to inflammatory disease, surgery, dysmenorrhoea, headache paracetamol - resembles NSAIDs and is effective as an analgesic, but lacks anti-inflammatory activity

26.08 OTHER ANALGESIC DRUGS Triptans

sumatriptan, zolmitriptan, eletriptan - antimigraine 5-HT1B and 5-HT1D receptor agonists

26.08 OTHER ANALGESIC DRUGS Dopamine receptor agonists

ropinirole, pramipexole, rotigotine - used to treat restless leg syndrome, which can be painful

26.08 OTHER ANALGESIC DRUGS Cannabinoids

nabilone, dronabinol - both synthetic cannabinoids nabiximols - natural cannabinoids strongest evidence for therapeutic benefit is for central neuropathic pain in multiple sclerosis

26 Analgesic drugs Flashcards

(40 cards)