Musculoskeletal Drugs and Analgesics

Question 1

List the 3 main types of opiate analgesia.

Answer 1

Codeine
Morphine
Oxycodone

Question 2

Describe the mechanism of action of opiates/opioids. (2)

Answer 2

1. Opioid receptor agonist: acts on mu, kappa and delta receptors on presynaptic neurons
2. This increases nociceptive thresholds throughout CNS and PNS

Question 3

List 3 indications for codeine.

List 3 indications for morphine.

List 3 indications for oxycodone.

Answer 3

CODEINE:
Mild-moderate pain
Persistent dry cough
Diarrhoea

MORPHINE:
Acute severe pain (incl. MI)
Acute pulmonary oedema
Chronic pain

OXYCODONE:
Moderate-severe pain in cancer
Post-op pain
Severe pain

Question 4

List 5 side effects of codeine.

Answer 4

Nausea
Vomiting
Constipation
Biliary spasm
Headache (on withdrawal)

Question 5

Describe the important pharmacokinetics/dynamics of codeine. (4)

Answer 5

Metabolised to morphine
Liver metabolism
Active metabolites excreted in urine (can accumulate in renal failure)
10% of population resistant to codeine (due to lack of demethylating enzyme which converts it to morphine)

Question 6

What would you tell the patient when prescribing codeine? (2)

Answer 6

Can be taken with paracetamol

Constipation is common

Question 7

List 6 side effects of morphine.

Answer 7

Nausea
Vomiting
Abdominal pain
Constipation
Respiratory depression
Sedation

Question 8

Describe the important pharmacokinetics/dynamics of morphine. (3)

Answer 8

Liver metabolism
Active metabolites can accumulate in renal failure
Accumulation can cause respiratory/CNS depression

Question 9

What would you tell the patient when prescribing morphine? (1)

Answer 9

Often given with anti-emetic to reduce N/V

Question 10

List 4 side effects of oxycodone.

Answer 10

Nausea
Vomiting
Abdominal pain
Constipation

Question 11

Describe the important pharmacokinetics/dynamics of oxycodone. (3)

What would you tell the patient when prescribing oxycodone? (1)

Answer 11

PHARMA:
Long/short acting preparations available
Liver metabolism
Admin: often slow IV/subcut infusion

PATIENT INFO:
Nausea and constipation are common

Question 12

What are the 2 types of NSAID?

Give some examples of each.

Answer 12

Non-selective NSAIDs, e.g.

• Ibuprofen
• Diclofenac

Selective NSAIDs, e.g.
-Celecoxib

Question 13

Describe the mechanism of action of NSAIDs.

What is the difference between non-selective and selective NSAIDs? What is the advantage of selective NSAIDs?

Answer 13

1. Inhibition of cyclo-oxygenase (COX 1/2) enzymes
2. This inhibits prostaglandin synthesis
   a. This decreases pain, inflammation and
   swelling

DIFFERENCE:
Non-selective: inhibit COX 1 and 2
Selective: only inhibit COX2 (WHY? GI side effects caused by COX1)

Question 14

List 3 indications for non-selective NSAIDs.

List 3 indications for selective NSAIDs.

Answer 14

NON-SELECTIVE:
Mild-moderate pain relief
Rheumatic disorders
Fever

SELECTIVE:
Osteoarthritis
RA
Ankylosing spondylitis

Question 15

List 6 side effects of NSAIDs.

Answer 15

Gastric/duodenal ulceration
Nausea
Diarrhoea
Thrombotic events
Renal impairment
Hyperkalaemia

Question 16

Describe the important pharmacokinetics/dynamics of non-selective NSAIDs. (3)

Answer 16

Avoid in:

• Pregnancy
• Renal impairment

Caution in:
-Elderly (risk of GI bleeds)

Question 17

What would you tell the patient when prescribing NSAIDs? (4)

Answer 17

Risk of GI bleeds on long term use
Take with food/milk
Take only when needed
Give PPI with NSAIDs (not needed with selective NSAIDs)

Question 18

Describe the important pharmacokinetics/dynamics of selective NSAIDs. (5)

Answer 18

Lower incidence of serious GI bleeds
Higher risk of CVD events

Avoid in:

• Renal impairment
• Pregnancy

Caution in:
-Elderly

Question 19

Describe the mechanism of action of paracetamol. (2)

Answer 19

1. Weak cyclo-oxygenase (COX) inhibitor, selective for brain COX
2. Lacks peripheral anti-inflammatory actions but inhibits prostaglandin synthesis in CNS

Question 20

List 2 indications for paracetamol.

Answer 20

Mild-moderate pain relief

Fever

Question 21

List 2 side effects of paracetamol.

Answer 21

Rash

Blood disorders

Question 22

Describe the important pharmacokinetics/dynamics of paracetamol. (2)

What would you tell the patient when prescribing paracetamol? (1)

Answer 22

PHARMA:
Avoid overdose - causes severe liver damage
Reduce dose to 500mg every 4 hours in patients <50kg

PATIENT INFO:
Avoid other OTC medications containing paracetamol

Question 23

Give 1 example of an xanthine oxidase inhibitor.

Answer 23

Allopurinol

Question 24

Describe the mechanism of action of allopurinol. (2)

Answer 24

1. Reduces synthesis of uric acid by competitively inhibiting xanthine oxidase
2. Reduces serum uric acid levels

Question 25

List 3 indications for allopurinol.

Answer 25

Gout
Calcium oxalate kidney stones
Hyperuricaemia associated with chemotherapy

Question 26

List 4 side effects of allopurinol.

Answer 26

Rash
Hypersensitivity
GI upset
Neutropenia

Question 27

Describe the important pharmacokinetics/dynamics of allopurinol. (3)

Answer 27

Do NOT start during acute attack (can exacerbate it)
CYP450 inhibitor
Affects azathioprine metabolism

Question 28

What would you tell the patient when prescribing allopurinol? (4)

Answer 28

Rash/GI upset relatively common
Rash should be reported to doctor
Keep taking allopurinol even with no symptoms
Often given with NSAID or colchicine