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Week 230 - Pain: What are the short-term side effects of morphine?

• Nausea and Vomiting
• Constipation
• Addiction


Week 230 - Pain: What are the long-term side effects of morphine?

• Hormonal imbalance (leading to reduced testosterone, reduced libido, erectile dysfunction, gynaecomastia, fatigue)
• Opioid-induced hyperalgesia.
• Immune system dysfunction.


Week 230 - Pain: How do opioids reduce testosterone?

• Inhibit GnRH
• Low gonadotrophin secretion.
• Reduced gonadal androgen (Testosterone) secretion.


Week 230 - Pain: What is nociceptive pain?

• Pain caused by signals sent by nociceptive receptors in tissues.


Week 230 - Pain: What is neuropathic pain?

• Pain caused by damage to the nerves themselves.


Week 230 - Pain: What are the five levels of Loeser's model of pain?

1) Nociceptive
2) Attitudes and Beliefs
3) Suffering
4) Pain escape behaviour
5) Social environment


Week 230 - Pain: What is the chronic pain cycle?

1) Pain
2) Fear of movement
3) Avoidance or over-activity
4) Rest
5) Distress, Frustration, Worry
6) Physically De-conditioned
1) Pain


Week 230 - Pain: Give examples of the two main types of drugs used for analgesia.

• Non-opioid analgesics:
- Paracetamol, Ibuprofen, Naproxen

• Opioid analgesics:
- Codeine, dihydrocodeine, fentanyl, morphine, oxycodone, tramadol.


Week 230 - Pain: Which two drugs, indicated for other uses, are commonly used for the treatment of pain?

Gabapentin and amitrityline.


Week 230 - Pain: What are the three steps of the WHO analgesia ladder?

1) Non-opioid analgesic. +/- adjuvants.
2) Weak opioid and non-opioid. +/- adjuvants.
3) Strong opioid and non-opioid. +/- adjuvants.


Week 230 - Pain: What are the adjuvants that may be added to analgesia treatment for pain?

• Bisphosphonates.
• Steroids.
• Muscle relaxants.
• Antidepressants.


Week 230 - Pain: Which opioids are classed as 'weak'?

Codeine and dihydrocodeine.


Week 230 - Pain: Which opioids are classed as 'strong'?

Morphine, fentanyl, oxycodone.


Week 230 - Pain: What is the mechanism of action of paracetamol?

• Reduces central prostaglandin synthesis.


Week 230 - Pain: How do NSAIDS work?

They are competitive inhibitors of COX.
- COX2 - Reduces prostaglandin secretion and therefore inflammation.
- COX1 - GI damage, Renal damage leading to sodium and water retention, Worsens asthma.


Week 230 - Pain: If a patient has any GI risk factors what should you add when prescribing NSAIDS?



Week 230 - Pain: What are the beneficial effects of opioids?

Analgesia, Euphoria, Sedation, Cough Suppression, Anti-diarrhoeal activity.


Week 230 - Pain: Tramadol also has non-opioid effects, what are they?

• Inhibits the re-uptake of norepinephrine (noradrenaline) and stimulates serotonin release.


Week 230 - Pain: What cautions should be taken when prescribing tramadol?

• Caution taken in patients with risk of seizures, increased risk of CNS toxicities if given with anti-depressants.


Week 230 - Pain: What are the side-effects of opioids?

Common - Nausea and vomiting, Drowsiness, Unsteadiness, Delirium
Occasional - Sweating, Dry mouth, Hallucinations, Pruritus,


Week 230 - Pain: What is the first-line strong opioid analgesic?



Week 230 - Pain: Which drug is used to reduce muscle spasm which may be causing pain?



Week 230 - Pain: What is gabapentin?

GABA analogue, reduces neuronal excitability.


Week 230 - Pain: What are the side-effects of gabapentin?

• Drowsiness, confusion, dizziness.


Week 230 - Pain: What are the side-effects of Amitriptyline?

• Drowsiness, arrhythmias, dry mouth, blurred vision.


Week 230 - Pain: Give examples of some of the local anaesthetics that can be used in the treatment of pain?

• Lidocaine patch
• Emla cream (Lidocaine, prilocaine)
• Nerve blocks.


Week 230 - Pain: What is the impact of Congenital Insensitivity to Pain (CIP)?

• Need to 'learn' to avoid dangerous behaviour.
• Musculoskeletal problems.
• Shorter life span.


Week 230 - Pain: What is the TRPV1 receptor?

• Capsaicin receptor.
• Pain receptor that reacts to thermal changes.
• It is activated by temperature above 43º.


Week 230 - Pain: Give examples of chemicals that cause sensitization of nociceptors and in turn produce the sensation of pain.

• Histamine
• Prostaglandins.
• Bradykinin.
• Substance P.


Week 230 - Pain: What are the two types of nociceptors?

• A∂ fibres.
• C-fibres.


Week 230 - Pain: What are the characteristics of A∂ (delta) nociceptors?

• Myelinated.
• 'Fast' pain sensation.
• Unimodal.


Week 230 - Pain: What are the characteristics of C nociceptors?

• Unmylinated.
• 'Slow' pain sensation.
• Unimodal.


Week 230 - Pain: When you, for eg bang your knee, you may rub it to alleviate the pain. What is the physiological basis behind this?

• The A-beta fibres are responsible for pressure sensation.
• These fibres travel along the same pathway into the spinal cord as A∂ and C fibres.
• A-beta stimulation can therefore inhibit the action of the A∂ and C fibres, through inhibitory interneurons, reducing the sensation of pain.


Week 230 - Pain: Pain travels through which spinal tract?

The spinothalamic, to the thalamus.


Week 230 - Pain: What are the 1st,2nd and 3rd order neurons in terms of the pain pathway?

1st - Nociceptor from pain stimulus to spinal cord.
2nd - Spinothalamic tract to thalamus.
3rd - Thalamocortical from thalamus to cortex.


Week 230 - Pain: At which level does the pain pathway cross the spinal cord?

They decussate at the same level that they enter.


Week 230 - Pain: Which parts of the cortex are responsible for the 'unpleasant' sensation of pain?

• Insula and Cingulate cortex.


Week 230 - Pain: Which part of the brain is responsible for locating the source of the pain?

Primary somatosensory cortex.


Week 230 - Pain: What are the three locations that the descending pathways of pain begin from?

• Periaquaductal grey.
• Nucleus raphe magnus.
• Locus coeruleus.


Week 230 - Pain: What are the receptor types for each of the locations of the descending pain pathway?

• Periaquaductal grey - Opioidergic
• Locus coeruleus - Noradrenergic
• Nucleus raphe magnus - Seretonergic


Week 230 - Pain: How does phantom limb pain arise?

• Massive loss of sensory input.
• Prolonged Nociceptive stimulation.
• There is a re-organisation in the dorsal horn, A-beta fibres may attach themselves to the remaining 2nd-order neurons causing stimulation of the pain pathway and a perception of pain in a limb that is no longer there.


Week 230 - Pain: What is the difference between opioids and opiates?

They are often used inter-changeably but in reality, opioids are endogenous ligands for opioid receptors. Whilst opiates are exogenous (e.g. morphine, codeine).


Week 230 - Pain: What type of receptors are opioid receptors? What are the main classes of opioid receptors?

• Metabotropic.
• Mu, Delta, Kappa.


Week 230 - Pain: Which class of opioid receptor is the most addictive?



Week 230 - Pain: What are the three types of opioids? Which receptor type does each have affinity for?

• Endorphins - Agonist for all three but primarily Mu.
• Enkephalins - Primarily a delta-agonist.
• Dynorphins - Primarily a kappa-agonist.


Week 230 - Pain: How do endogenous opioids modulate the pain pathway?

• Spinal interneurones release enkephalins into the synapse between the 1st and 2nd order pain neurons.
• These shutdown synaptic activity by inhibiting neurotransmitter release and hyper-polarizing the postsynaptic membrane.
• The interneurons themselves are controlled by opioids.


Week 230 - Pain: What are the other effects of opioids?

• Euphoria
• Sedation
• Cough suppression
• Respiratory depression
• Nausea and Vomiting
• Constipation
• Miosis


Week 230 - Pain: What is Allodynia?

A stimulus that causes pain when it shouldn't.


Week 230 - Pain: What is trigeminal neuralgia? How is it treated?

• An intense episodic pain that is caused by compression of the trigeminal nerve.
• It is often triggered by stimulation of the sensory areas of the trigeminal nerve.
• It is treated with anti-convulsants e.g. Carbamazapine.