6. Pain Flashcards
Different types of pain
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)
Pain treatment
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
Types of analgesics
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)
Paracetamol dose and counselling
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.
Paracetamol overdose
This applies to tablets, soluble tablets, capsules
Overdose: Liver damage (higher risk <50kg)
Treated with Acetylcysteine
Aspirin dose
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
Aspirin side effects
GI-irritation
Enteric formulations can prevent this by bypassing the stomach and dissolving in the small intenstine.
Tinnitus
At higher doses
Aspirin contraindications
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
Opioid mechanism of action
Opioids act on the opioid μ receptors in the CNS
Opioid side effects
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
Opiods side effects
- 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
Opioid side effects
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
Opioid interactions
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
Codeine and dihydrocodeine are weak opioids. What route should it never by given by?
Can never be given intravenously
Codeine for coughs and colds, contraindications
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
If codeine is being used in children for analgesia, what is the dose?
12+ years: For 3 days only, max 240mg daily every 6 hours
Tramadol side effects
Also acts on the serotonergic, noradrenergic pathways, unlike other opioids, therefore responsible for:
- Psychiatric reactions
- Reduced seuzire thresholds
Tramadol interactions
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
Morphine dose and route
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
Diamorphine dose
Dose: 1/2 the oral morphine dose
Route: Preferred in palliative care
Morphine side effects
- Nausea and vomting
- Euphoria
Diamorphine vs morphine
More soluble than morphine. Better choice in palliative care to avoid fluid overload.
Also causes less nausea than morphine
Diamorphine side effects
- Hypotension
- Nausea
Breakthrough pain
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
Buprenorphine and fentanyl
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
Buprenorphine side effect
- Withdrawal
Nalaxone partially reverses burpenorphine. Which means pain is not completely masked
Buprenorphine dose
Can be given as 72hour patches, 4 day patches and 7 day patches.
Fentanyl patch duration
72 hour patches
Fentanyl side effects
- 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
Transdermal patch application
- 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
What is a migraine
A moderate-severe headache that is unilateral and pulsating.
It is episodic: <15 days/month
Or
Chronic: ≥ 15 days/month
Migraine symptoms
- 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
Migraine and combined oral contraceptives
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
Drugs used to treat migraine attacks
5-HT1 Receptor agonist
* Almotriptan
* Sumatriptan
* Rizatriptan
Anti-emetics
* Domperidone
* Metoclopramide
* Prochlorperazine
Oral analgesics
* Paracetamol
* Aspirin
* Ibuprofen
* Diclofenac
Acute migraine attack treatment
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
Migraine prevention
1st line: Propanolol
If unsuitable, offer another beta blocker: atenolol, bisoprolol, metoprolol, nadolol, timolol
If unsuitable: topiramate
5-HT1 receptor agonist “triptans” mechanism of action
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
5-HT1 receptor agonist “triptans” dose
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.
5-HT1 receptor agonist “triptans” side effects
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.
5-HT1 receptor agonist “triptans” interactions
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
Cluster headaches
Sharp, peircing pain around the eye.
Usually happens at the same time of day or year.
Headaches last between 15 minutes to 3 hours
Cluster headache treatment
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.
