Management of Chronic Pain

Question 1

Describe acute pain.

Answer 1

• Usually ass. with obvious tissue damage.
• Protective function.
• Due to increased nervous system activity.
• Pain resolves upon healing.

Question 2

Describe chronic pain.

Answer 2

• Pain beyond the expected period of healing.
• No longer serves useful purpose.
• Changes in pain signalling and detection.
• Degrades health and function.

Question 3

Chronic pain can be divided into what two categories?

Answer 3

• Chronic cancer.

- Chronic non-cancer pain.

Question 4

Chronic pain is probably not directly related to initial injury/disease, but secondary to?

Answer 4

Physiological changes in pain signalling and detection.

Question 5

Observed behaviours that suggest pain in a patient?

Answer 5

• Grimacing.
• Rigid posture.
• Limping.
• Frowning or crying.

Question 6

What physiological responses may occur in response to pain?

Answer 6

• Increased BP.
• Increased pulse rate.
• Increased respiration rate/ deep breathing.

Question 7

Painful stimuli in the skin are relayed to the brain via?

Answer 7

• Lamina I (NK1 receptor) > parabrachial > Amygdala hypothalamus - AFFECTIVE component of pain.
• Lamina V > Thalamus > Somatosensory Cortex - SENSORY component of pain.

Question 8

What is nociceptive pain?

Answer 8

An appropriate physiologic response to painful stimuli via an intact nervous system.

Question 9

What is neuropathic pain?

Answer 9

Inappropriate and abnormal sensations due to nervous system dysfunction.

Question 10

Define allodynia.

Answer 10

Pain from a stimulus that would not normally be painful e.g. cotton wool.

Question 11

Define hyperalgesia.

Answer 11

Pain is heightened beyond that which would be expected from a painful stimulus e.g. pin prick.

Question 12

Give an example of a cause of neuropathic pain.

Answer 12

• Shingles, post-herpetic neuralgia.
• Surgery.
• Trauma.
• Diabetic neuropathy.
• Amputation.
• Idiopathic,

Question 13

What is neuroplasticity?

Answer 13

The process by which the brain’s neural synapses and pathways are altered as a result of environmental/ behavioural/ neural changes.

Question 14

Chronic pain is associated with morphological changes in what?

Answer 14

The CNS.

Question 15

What is the initial WHO ladder approach to pain management (not adjuvants)?

Answer 15

1. Non-opioid analgesics e.g. NSAIDs, Paracetamol.

2. Opioid analgesics e.g. Tramadol, Codeine, Morpine, Oxycodone.

Question 16

What are the adjuvants in the WHO ladder, following non-opioid and opioid drugs?

Answer 16

• Anti-depressants e.g. Amitriptyline, Duloxetine.
• Anti-convulsants e.g. Gabapentin, Pregabalin.
• Topical analgesics e.g. Capsaicin, Lidocaine 5% plaster.

Question 17

What follows on from adjuvants in the WHO ladder pharmacological approach to pain?

Answer 17

• Local anaesthesia.

- Peripheral nerve or nerve plexus block.

Question 18

Mechanism of action of NSAIDs?

Answer 18

Inhibition of the enzyme Cyclooxygenase (COX) and thus inhibits prostaglandin synthesis.

Question 19

By inhibiting prostaglandins, NSAIDs achieve what?

Answer 19

Reduction in tissue inflammation and pain.

Question 20

Give an example of an NSAID?

Answer 20

• Aspirin, Ibuprofen.

Question 21

What are NSAIDs most effective against?

Answer 21

Nociceptive pain.

Question 22

Side effects of NSAIDs?

Answer 22

• GI irritation/bleeding.
• Renal toxicity.
• Potential drug-drug interactions.
• CV side effects (MI, stroke, hypertension).

Question 23

NSAIDs mainly act where?

Answer 23

Peripherally.

Question 24

Selective COX inhibitors are more potent where?

Answer 24

At COX2-enzymes.

Question 25

Paracetamol is what class of drug?

Answer 25

Aniline derivative.

Question 26

Efficacy of paracetamol?

Answer 26

- Analgesic and antipyretic effects. | - No anti-inflammatory action.

Question 27

Mode of action of paracetamol?

Answer 27

- Inhibition of central prostaglandin synthesis.

Question 28

Side effect of paracetamol?

Answer 28

Risk of toxic liver damage.

Question 29

Paracetamol mainly acts where?

Answer 29

Centrally.

Question 30

Give an example of a weak opioid.

Answer 30

- Tramadol, Codeine.

Question 31

Give an example of a strong opioid.

Answer 31

- Morphine, Oxycodone.

Question 32

Efficacy of opioid analgesics?

Answer 32

- Mainly effective in nociceptive pain. - Less effective in chronic states. - Partially effective in neuropathic pain.

Question 33

Mode of action of opioid analgesics?

Answer 33

- Activate endogenous analgesic system. - Stimulate receptors in limbic system to eliminate subjective feeling of pain. - Affect descending pathways that modulate pain perception. - Reduce ascending pain signal transmission in the spinal cord.

Question 34

S/E of opioids?

Answer 34

Nausea, vomiting, constipation, dizziness/vertigo, somnolence, dry skin, pruritus.

Question 35

Opioids mainly act where?

Answer 35

On the CNS. They are predominantly agonists of morphine (mu) receptors present in brain and spinal cord.

Question 36

Efficacy of the anti-depressants - TCAs?

Answer 36

- Neuropathic pain. - Complex regional pain syndrome. - Tension headaches.

Question 37

The anti-depressants - TCAs mode of action in pain?

Answer 37

Inhibition of neuronal reuptake of noradrenaline and serotonin (5-HT). (- The key neurotransmitters involved in pain signalling).

Question 38

Side effects of the anti-depressants - TCA)?

Answer 38

- Constipation, dry mouth, somnolence, abnormalities in heart rate or rhythm, insomnia and increased appetite.

Question 39

In whom should TCAs be used with caution?

Answer 39

- History of CV disease. - Glaucoma. - Urinary retention. - Autonomic neuropathy.

Question 40

Efficacy of the anti-depressants Selective Serotonin and Noradrenaline Reuptake Inhibitors (SSRIs and SNRIs)?

Answer 40

- Neuropathic pain. | - SNRIs are better analgesics than SSRIs.

Question 41

SSRIs selectively inhibit?

Answer 41

Reuptake of serotonin from the synaptic cleft.

Question 42

SNRIs selectively inhibit?

Answer 42

Reuptake of noradrenaline from the synaptic cleft.

Question 43

How do SNRIs and TCAs differ?

Answer 43

SNRIs have little affinity for adrenergic, cholinergic or histaminergic receptors and thus are not associated with S/E linked to inhibition of these systems.

Question 44

Mode of action of SSRIs and SNRIs?

Answer 44

- Selectively inhibit reuptake of noradrenaline or serotonin, or both. - Provide analgesia by intensifying descending inhibition.

Question 45

S/E of SSRIs and SNRIs?

Answer 45

- Nausea + vomiting, constipation, somnolence, dry mouth, increased sweating, loss of appetite.

Question 46

Example of SNRIs?

Answer 46

- Duloxetine, Venlafaxine.

Question 47

Example of SSRI?

Answer 47

- Citalopram. Fluoxetine.

Question 48

Example of anti-convulsants?

Answer 48

- Carbamazepine, Gabapentin, Pregabalin.

Question 49

Efficacy of anticonvulsants?

Answer 49

- Neuropathic pain.

Question 50

Mode of action of the anti-convulsant Gabapentin?

Answer 50

- Binds to presynaptic voltage-dependent Ca2+ channels.

Question 51

Mode of action of the anti-convulsant Pregabalin?

Answer 51

- Interacts with special N-type Ca2+ channels.

Question 52

Mode of action of the anti-convulsant Carbamazepine?

Answer 52

- Blocks Na+ and Ca2+ channels.

Question 53

S/E of anti-convulsants?

Answer 53

- Sedation, dizziness, ataxia, peripheral oedema, nausea, weight gain.

Question 54

Describe the general mode of action of anti-convulsants?

Answer 54

Drugs that inhibit neuronal excitation and stabilise nerve membranes by blocking CNS ion channels.

Question 55

Main indication for anti-convulsants in pain therapy?

Answer 55

Shooting neuropathic pain e.g. trigeminal neuralgia, post-herpetic and other neuralgias.

Question 56

Main categories of topical analgesics?

Answer 56

- Rubefacients. - Capsaican and capsicum extracts and derivatives. - NSAIDs. - Lidocaine. - Levomenthol.

Question 57

Describe Rubefacients.

Answer 57

- Topical analgesic. | - Traditional formulation based on salicylate and nicotinate esters.

Question 58

Describe the forms of Capsaicin and Capsicum extracts and derivatives used as topical analgesia.

Answer 58

- Capsaicin 0.025%. | - Capsaicin (QTENZA) 8% patch.

Question 59

Give an example of an NSAID that may be used as a topical analgesic.

Answer 59

- Diclofenac, Felbinac, Ibuprofen, Ketoprofen, Piroxicam, Naproxen, Flurbiprofen.

Question 60

How is lidocaine applied as a topical analgesic?

Answer 60

- 5% medicated plaster.

Question 61

What strength of Levomenthol is used as a topical analgesic?

Answer 61

0.5-2%.

Question 62

Topical analgesics reduce pain impulses transmitted by?

Answer 62

- A-delta-fibres. | - C-fibres.

Question 63

Main S/E of topical analgesia?

Answer 63

- Localised application site reactions e.g. rash, pruritus, erythema.

Question 64

When deciding on pharmacological management of neuropathic pain, what should be discussed?

Answer 64

- Benefits vs s/e of chosen treatments. - Why a treatment is being offered. - Coping strategies for pain + possible adverse effects of treatment. - Non-specialist offerings vs referral specialist services.

Question 65

What types of psychological therapies may benefit those with pain esp. if chronic?

Answer 65

- CBT. - Solution focused brief therapy. - Hypnosis, relaxation therapy and psychotherapy.

Question 66

How does CBT work?

Answer 66

Cognitive behavioural therapy challenges and modifies negative thoughts/feelings/behaviours.