6. Pain

Question 1

Different types of pain

Answer 1

Nociceptive - tissue damage

Neuropathic -Nerve damage (burning, prickling, stabbing sensation)

Nociceptive - sensitisation changes in pain pathway

Further split into
primary (no cause) vs secondary pain (related to an underlying condition)

Question 2

Pain treatment

Answer 2

WHO analgesic ladder

For mild pain
Step 1: Non-opioid (paracetamol, NSAIDs)

For mild-moderate pain
Step 2: Weak opioid (codeine, dihydrocodeine, tramadaol)

For moderate-severe pain:
Step 3: Strong opiod: (morphine, fentanyl patches)

+/- Adjuvants:
Tricyclic antidepressants: Amitryptiline, Nortryptiline
Antiepiletics: Gabapentin, Pregablin
Nerve compression: dexamethasone
Bone metastases: Bisphosphonates
Muscle spasm: Benzodiazepines

Question 3

Types of analgesics

Answer 3

Non-opioid:
Aspirin
Nefopam
NSAID
Paracetamol

Weak opiod:
Codeine (CD5, CD2-injection)
Dihydrocodeine (CD5)
Meptazinol (POM)
Tramadol (CD3)

Strong opioid:
Buprenorphine (CD3)
Diamorphine
Fentanyl (CD2)
Hydromorphone (CD2)
Morphine (CD2, CD5<13mg/5ml)
Oxycodone (CD2)

Question 4

Paracetamol dose and counselling

Answer 4

0.5-1g every 4-6 hours PRN (max 4g per day)

Label: Do not take more than 2 at any time. Do not take more than 8 in 24 hours.

Label: Contains paracetamol. Do not take anything else containing paracetamol while taking this medicine. Talk to a docotr at once if you take too much of this mdicine even if you feel unwell.

Question 5

Paracetamol overdose

Answer 5

This applies to tablets, soluble tablets, capsules

Overdose: Liver damage (higher risk <50kg)

Treated with Acetylcysteine

Question 6

Aspirin dose

Answer 6

300-900mg every 4-6 hours (max 4g per day)

Label: Do not take anything else containing aspirin while taking this medicine

Label: Take with or just after food or meal

Question 7

Aspirin side effects

Answer 7

GI-irritation
Enteric formulations can prevent this by bypassing the stomach and dissolving in the small intenstine.

Tinnitus
At higher doses

Question 8

Aspirin contraindications

Answer 8

Contraindicated in individuals under 16
Aspirin is a salicylate - so cannot be used in children under 16 years, due to risk of Reye’s syndrome.

Exceptions: kawasaki disease, or as an antiplatelet

Contraindicated in people with NSAID hypersensitivity
e.g bronchospasm, asthma attack, rhinitis, urticaria

Question 9

Opioid mechanism of action

Answer 9

Opioids act on the opioid μ receptors in the CNS

Question 10

Opioid side effects

Answer 10

Tolerance - higher doses needed to achieve the same analgesia.
Patients must be warned of signs of tolerance: respiratory depression, pinpoint pupils, coma

Physical dependence - Appears on abrupt withdrawal

Psychological dependence -compulsive and continued use despite harm.
If addiction and dependence occurs: agree treatment strategy, withdrawal pain and monitor regularly

Must be used in caution in substance use, mental health disorder

Question 11

Opiods side effects

Answer 11

• Respiratory depression - make breathing slow and shallow

Increased risk of this with benzodiazepines

Antidote: Naloxone (however only partially reverses effects for buprenorphine)

• Nausea and vomiting - as opioids work on the CTZ.
  Antiemetic metoclopramide is useful
• Constipation
  Osmotic + stimulant laxative
• Sedation
  Should avoid driving and alcohol (also CNS depressant)
• Hallucinations and Euphoria
• Pupil constriction
  Contra-indicated in heady injury or neurological assesments
• Dry mouth
• Hypotension
• Hyperalgesia is a long term effect
  Treated by reducing dose or switching treatment, initiated by specialist

Question 12

Opioid side effects

Answer 12

M - miosis (pinpoint pupils), muscle rigidity
O - out of it (sedation)
R- respiratory depression
P - postural hypotension
H - hyperalgesia hallucinations
I - Infrequency
N - Nausea and vomiting
E - Euphoria

Question 13

Opioid interactions

Answer 13

Interacts with other CNS depressants, as there is an increased risk of CNS depression, i.e sedation

Alcohol, benzodiazepines, Z-drugs, antihistamines (sedating), antipsychotic, barbiturates, irreversible MAOIs

Question 14

Codeine and dihydrocodeine are weak opioids. What route should it never by given by?

Answer 14

Can never be given intravenously

Question 15

Codeine for coughs and colds, contraindications

Answer 15

Should never be used by a breastfeeding mum

Should not be used by a child under 12 years as it is associated with respiratory side effects

Should not be used by people who are ultra-rapid metabolisers

Question 16

If codeine is being used in children for analgesia, what is the dose?

Answer 16

12+ years: For 3 days only, max 240mg daily every 6 hours

Question 17

Tramadol side effects

Answer 17

Also acts on the serotonergic, noradrenergic pathways, unlike other opioids, therefore responsible for:

• Psychiatric reactions
• Reduced seuzire thresholds

Question 18

Tramadol interactions

Answer 18

Tramadol is a serotonergic drug. It interacts with serotonergic drugs to increase the risk of serotonin syndrome

Antidepressants (TCA, SSRI, MAOI), Amfetamines, Lithium, MAO-B e.g selegiline, methadone, St John’s wort, 5-HT1 agonists, e.g sumatriptan, 5-HT3 receptor antagonist e.g ondansetron

Question 19

Morphine dose and route

Answer 19

Oral morphine: Taken every 4 hours
Patients may also be put on a modified release preparation taken every 12 or 24 hours

Route: 1/2 the oral dose

Morphine also used in dyspnoea in palliative care, as it slows breathing, making it easier to breathe

Question 20

Diamorphine dose

Answer 20

Dose: 1/2 the oral morphine dose

Route: Preferred in palliative care

Question 21

Morphine side effects

Answer 21

• Nausea and vomting
• Euphoria

Question 22

Diamorphine vs morphine

Answer 22

More soluble than morphine. Better choice in palliative care to avoid fluid overload.
Also causes less nausea than morphine

Question 23

Diamorphine side effects

Answer 23

• Hypotension
• Nausea

Question 24

Breakthrough pain

Answer 24

Sudden pain that breaks through between regular doses of pain medication.
If this occurs rescue doses are offered, as an immediate release medication.

Rescue doses: 1/10th -1/6th of the total daily dose, given every 2-4 hours as required.

Immediate-release preparation examples:
Oral morphine, oxycodone

Question 25

Buprenorphine and fentanyl

Answer 25

Unsuitable in mild pain and in rapidly changing pain levels as they have a long action and cannot be rapidly titrated to match pain levels

Question 26

Buprenorphine side effect

Answer 26

* Withdrawal Nalaxone partially reverses burpenorphine. Which means pain is not completely masked

Question 27

Buprenorphine dose

Answer 27

Can be given as 72hour patches, 4 day patches and 7 day patches.

Question 28

Fentanyl patch duration

Answer 28

72 hour patches

Question 29

Fentanyl side effects

Answer 29

* Respiratory depression Should not be used in opioid naive patients Must safely dispose patches, to prevent accidental exposure in children Signs of opioid toxicity: respiratory depression, pinpoint pupils Must remove patch if experiencing breathing difficulties or impaired speech

Question 30

Transdermal patch application

Answer 30

* Should be applied to dry, non-irritated, non-hairy skin on the upper arm or torso * Rotate patch site to prevent the skin form becoming itchy or sore * Avoid hot baths and saunas

Question 31

What is a migraine

Answer 31

A moderate-severe headache that is unilateral and pulsating. It is episodic: <15 days/month Or Chronic: ≥ 15 days/month

Question 32

Migraine symptoms

Answer 32

* Throbbing pain on one side * Nausea and vomiting due to reduced gastric motility and emptying * Sensiitvity to light Aura (warning lights) **Visual** - flickering lights, zizags **Dysphasia** - impaired ability to use or understand words **Sensory**: numbness, tingling **Dizziness**, **Off-balance**

Question 33

Migraine and combined oral contraceptives

Answer 33

If you have migraine with aura, you should not take the combined oral contraceptive pill. This is because the combined pill is associated with a very small increased risk of stroke. This risk increases when the pill is taken by women who have migraine with aura. Much preferred to take progestogen only contraceptives

Question 34

Drugs used to treat migraine attacks

Answer 34

**5-HT1 Receptor agonist** * Almotriptan * Sumatriptan * Rizatriptan **Anti-emetics** * Domperidone * Metoclopramide * Prochlorperazine **Oral analgesics** * Paracetamol * Aspirin * Ibuprofen * Diclofenac

Question 35

Acute migraine attack treatment

Answer 35

**1st line:** Aspirin/ibuprofen OR 5-HT1 receptor agonist (sumatriptan) **2nd line:** Sumatriptan AND Naproxen If nausea/vomiting is present: metoclopramide or domperidone as they promote gastric motility and emptying (prokinetic antiemetics). This improves absorption of analgesics. Overuse medication may cause tolerance. Treatment should be limited to max 2 days a week

Question 36

Migraine prevention

Answer 36

**1st line:** Propanolol If unsuitable, offer another beta blocker: atenolol, bisoprolol, metoprolol, nadolol, timolol **If unsuitable:** topiramate

Question 37

5-HT1 receptor agonist "triptans" mechanism of action

Answer 37

Prevent the release of neuropeptides which are involved in the pain pathway Act on 5-HT1B/1D receptors and cause vasoconstriction of the cranial blood vessels

Question 38

5-HT1 receptor agonist "triptans" dose

Answer 38

Used in acute migraine One dose should be taken ASAP after onset. A second dose should be taken 2 hours later. If the drug is naratriptan, the second dose should be taken 4 hours later. A second dose should not be taken for the same attack.

Question 39

5-HT1 receptor agonist "triptans" side effects

Answer 39

As triptans work by constricting cranial blood vessels, their action also extends to constricting other blood vessels: coronary arteries. Patients must stop if they experience: heat, tightness in the chest or throat **Can cause high blood pressure and ischaemia due to reduced blood oxygen supply.** Therefore contra-indicated in cardiovascular conditions: angina, myocardial infarction, stroke, transient ischaemic stroke, moderate-severe uncontrolled hypertension.

Question 40

5-HT1 receptor agonist "triptans" interactions

Answer 40

**5-HT1 agonists is a serotonergic drug. It interacts with serotonergic drugs to increase the risk of serotonin syndrome** ​ Antidepressants (TCA, SSRI, MAOI), Amfetamines, Lithium, MAO-B e.g selegiline, methadone, St John's wort, 5-HT1 agonists, e.g sumatriptan, 5-HT3 receptor antagonist e.g ondansetron

Question 41

Cluster headaches

Answer 41

Sharp, peircing pain around the eye. Usually happens at the same time of day or year. Headaches last between 15 minutes to 3 hours

Question 42

Cluster headache treatment

Answer 42

Cluster headaches rarely respond to standard analgesics Sumatriptan is given by subcutaneous injection. Sumatriptan nasal spray or zolmitriptan nasal spray can be used if injection is unsuitable.