Musculoskeletal and Pain Drugs

Question 1

give some examples of opiates?

Answer 1

codeine
morphine
oxycodone

Question 2

what is the MoA for codeine and morphine and oxycodone?

Answer 2

Opioid receptor agonist; acts on mu, kappa and delta on presynaptic neurones. This gives numerous effects that increase nociceptive thresholds throughout the CNS and PNS.

Question 3

what are the indications for codeine?

Answer 3

Mild to moderate pain
Persistent dry cough
Diarrhoea

Question 4

list some side effects of codeine:

Answer 4

Nausea
Vomiting
Constipation
Biliary spasm
Headache on withdrawal

Question 5

what is important clinically regarding pharmacokinetics/dynamics for codeine?

Answer 5

Metabolised to morphine which is responsible for analgesic effects.
Predominantly metabolised by the liver.
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

Question 6

what info should be given to patient before starting on codeine?

Answer 6

Can be taken with paracetamol for a better analgesic effect.

Constipation is a likely side effect.

Question 7

what are the indications for morphine?

Answer 7

Acute severe pain (including in setting of myocardial infarction)
Acute pulmonary oedema
Chronic pain

Question 8

what are some side effects of morphine?

Answer 8

Nausea
Vomiting
Abdominal pain
Constipation
Respiratory depression
Sedation

Question 9

what is important clinically regarding pharmacokinetics/dynamics for morphine?

Answer 9

Predominantly metabolised by the liver.
Metabolites are active and can accumulate in renal failure.
Accumulation can result in respiratory and CNS depression.

Question 10

what info should be given to patient before starting on morphine?

Answer 10

Often given with an anti-emetic to reduce nausea / vomiting.

Question 11

what are the indications for oxycodone

Answer 11

Moderate to severe pain relief in cancer patients
Postoperative pain
Severe pain

Question 12

list some side effects of oxycodone:

Answer 12

Nausea
Vomiting
Abdominal pain
Constipation

Question 13

what is important clinically regarding pharmacokinetics/dynamics for oxycodone?

Answer 13

Available as long and short acting preparations
Predominantly metabolised by the liver.
Often administered via slow intravenous/subcutaneous infusion.

Question 14

what info should be given to patient before starting on oxycodone?

Answer 14

Nausea and constipation are common side-effects.

Question 15

give examples of non selective NSAIDs?

Answer 15

ibuprofen

diclofenac

Question 16

what is the MoA of non selective NSAIDs?

Answer 16

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.

Question 17

what are the indications for non selective NSAIDs?

Answer 17

Mild to moderate pain relief
Rheumatic disorders (such as rheumatoid arthritis and osteoarthritis)
Fever (anti-pyretic effect)

Question 18

list some side effects of non selective NSAIDs?

Answer 18

Gastric and duodenal ulceration
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

Question 19

what is important clinically regarding pharmacokinetics/dynamics for non selective NSAIDs?

Answer 19

Pain relief starts soon after the first dose, full analgesic effects can take up to one week and anti-inflammatory effects can take up to three weeks.
Avoid in patients with renal impairment – use lowest dose, for shortest time if unavoidable.
Caution should be used in the elderly – risk of gastrointenstinal bleeds.

Question 20

what info should be given to patient before starting on non selective NSAIDs?

Answer 20

Risk of stomach bleeds if on long-term use.
Take with food or milk, to reduce abdominal discomfort and to reduce the risk of bleeding.
Take only when required.
In elderly patients a proton pump inhibitor is usually given alongside NSAID drugs

Question 21

what are some examples of selective NSAIDs?

Answer 21

Celecoxib

Question 22

what is the MoA for selective NSAIDs?

Answer 22

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 COX-1 inhibition

Question 23

what are the indications for selective NSAIDs

Answer 23

Pain and inflammation in: osteoarthritis / rheumatoid arthritis / ankylosing spondylitis

Question 24

list some side effects of selective NSAIDs?

Answer 24

Gastric and duodenal ulceration (Risk increases with duration of therapy and dosage)
Nausea
Diarrhoea
Renal impairment
Hyperkalaemia

Question 25

what is important clinically regarding pharmacokinetics/dynamics for selective NSAIDs?

Answer 25

Less incidence of serious GI bleeds / ulceration compared to non-selective. Presumed higher risk of CV events, compared to non-selective. Avoid in patients with renal impairment – use lowest dose, for shortest time if unavoidable. Caution should be used in the elderly – risk of GI bleeds. Avoid in pregnancy particularly 3rd trimester

Question 26

what info should be given to patient before starting on selective NSAIDs?

Answer 26

Risk of stomach bleeds if on long-term use. Take with food or milk, to reduce abdominal discomfort and to reduce the risk of bleeding. Take only when required.

Question 27

what is the MoA for paracetamol?

Answer 27

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.

Question 28

what are the indications for paracetomal

Answer 28

Mild to moderate pain relief | Fever (anti-pyretic effect)

Question 29

list some side effects of paracetamal

Answer 29

Rash / blood disorders

Question 30

what is important clinically regarding pharmacokinetics/dynamics for paracetamol

Answer 30

Overdose must be avoided – severe liver damage can occur and can be fatal. Careful dosing in younger patients and patients with low body weight (reduce dose to 500mg 4-6 hourly, qid in patients <50kg)

Question 31

what info should be given to patient before starting paracetamol?

Answer 31

Take only the prescribed amount and be wary of other over-the-counter medications that may contain paracetamol.

Question 32

what is an example of a xanthine oxidase inhibitor?

Answer 32

allopurinol

Question 33

what is the MoA for allopurinol?

Answer 33

Reduces synthesis of uric acid by competitively inhibiting xanthine oxidase. Reduces serum uric acid level

Question 34

what are the indications for allopurinol?

Answer 34

Prophylaxis of gout Prophylaxis of calcium oxalate renal stones Hyperuricaemia associated with cancer chemotherapy

Question 35

list some side effects of allopurinol:

Answer 35

Rash Hypersensitivity Gastrointestinal disturbances Neutropenia (rare)

Question 36

what is important clinically regarding pharmacokinetics/dynamics for allopurinol?

Answer 36

Not used to treat acute attack of gout, can exacerbate the inflammation, so should not be started during acute episodes. Cytochrome P450 enzyme inhibitor Azathioprine metabolism affected.

Question 37

what info should be given to patient before starting allopurinol?

Answer 37

Rash and abdominal disturbances are relatively common. - report to Dr. Keep taking allopurinol, even when there is no sign of gout. In order to prevent an exacerbation of gout a NSAID or cochicine is often prescribed for the first 3 months of therapy