MSK/Pain Flashcards
Give examples of opiates:
Codeine, oxycodone and morphine
What is the mechanism of action of codeine?
Opioid receptor agonist which acts on mu, kappa and delta on presynaptic neurones.
This increases nociceptive thresholds in the CNS and PNS.
Metabolised to morphine by the liver which is responsible for analgesic effects.
Active metabolites are excreted in the urine so can accumulate in renal failure.
10% of population resistant to codeine’s analgesic properties as they lack the demethylating enzyme that
converts it to morphine.
What are side effects of codeine?
Nausea Vomiting Constipation Biliary spasm Headache on withdrawal
When is codeine prescribed?
Mild to moderate pain
Persistent dry cough
Diarrhoea
What is the mechanism of action of morphine?
Opioid receptor agonist; acts on mu, kappa and delta on presynaptic neurones. This gives numerous
effects that increase nociceptive thresholds throughout the central and peripheral nervous system.
Predominantly metabolised by the liver.
Metabolites are active and can accumulate in renal failure.
Accumulation can result in respiratory and central nervous system depression.
When would morphine be prescribed?
Acute severe pain (including in setting of myocardial infarction)
Acute pulmonary oedema
Chronic pain
What are side effects of morphine?
Nausea Vomiting Abdominal pain Constipation Respiratory depression Sedation
When is oxycodone prescribed?
Moderate to severe pain relief in cancer patients
Postoperative pain
Severe pain
What is the mechanism of action of oxycodone?
Opioid receptor agonist; acts on mu, kappa and delta on presynaptic neurones. This gives numerous
effects that increase nociceptive thresholds throughout the central and peripheral nervous system.
Available as long and short acting preparations
Predominantly metabolised by the liver.
Often administered via slow intravenous/subcutaneous infusion.
What are side effects of oxycodone?
Nausea
Vomiting
Abdominal paln
Constipation
What is the mechanism of action of NSAIDs?
Non-selective inhibition of cyclo-oxygenase (COX 1 and 2) enzymes, decreasing key inflammatory
mediator prostaglandin from being synthesised.
Thereby reduces pain, inflammation and swelling.
When would NSAIDs be prescribed?
Mild to moderate pain relief
Rheumatic disorders (such as rheumatoid arthritis and osteoarthritis)
Fever (anti-pyretic effect)
What are side effects of NSAIDs?
Gastric and duodenal ulceration (risk increases with duration of therapy and dosage)
Nausea
Diarrhoea
Small increased risk of thrombotic events even when used short term, particularly diclofenac and high
dose ibuprofen.
Avoid in pregnancy particularly 3rd trimester (risk of closure of fetal ductusarteriosus in utero and
pulmonary hypertension in newborn)
Renal impairment
Hyperkalaemia
Give examples of NSAIDs:
Ibuprofen
Diclofenac
What is the mechanism of action of selective NSAIDs?
Mechanism of action:
Selective inhibitor of COX-2, decreasing key inflammatory mediator prostaglandin From being
synthesised.
Thereby reduces pain, inflammation and swelling.
The gastrointestinal side effects are mediated via dix-1 inhibition
Give an example of a selective NSAID:
Celecoxib
What are the side effects of selective NSAIDs?
Gastric and duodenal ulceration (Risk increases with duration of therapy and dosage) Nausea Diarrhoea Renal impairment Hyperkalaemia
When are selective NSAIDs prescribed?
Pain and inflammation in: osteoarthritis / rheumatoid arthritis / ankylosing spondylitis
What is the mechanism of action of paracetamol?
A weak cyclooxygenase enzyme (COX) inhibitor with selectivity for brain COX.
It therefore lacks peripheral anti-inflammatory actions but is useful in increasing the threshold for
nociceptive activation by inhibiting prostaglandin synthesis and its effects centrally.
When is paracetamol prescribed?
Mild-moderate pain relief
Fever (anti-pyretic)
What are side effects of paracetamol?
Rarely rash/blood disorders
Give an example of a xanthine oxidase inhibitor:
Allopurinol
What is the mechanism of action of Allopurinol
It is a xanthine oxidase inhibitor which reduces uric acid synthesis by competitively inhibiting xanthine oxidase and reduces serum uric acid levels
When would allopurinol be prescribed?
Prophylaxis of gout or calcium oxaletate renal stones
Hyperuricaemia associated with chemotherapy
