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Flashcards in Pain Deck (23):

What is the purpose of acute pain?

1. Warning of tissue damage
2. Immobilisation for healing
3. Protection of species


What physiological effects does pain cause?

Increased HR, BP, RR and decreased GIT


What are the 3 classifications of pain? (nerve-related)

1. Nociceptive (chemicals in body stimulate nerve)
2. Neuropathic (direct damage or disease of nerve)
3. Mixed (most)


What are the 2 types of pain, and what are their subdivisions?

1. Acute (less than 7 days) either post-operative or non-surgical cause
2. Chronic - either cancer pain or non cancer pain


What are the two types of nerve fibres that transmit pain, and what kind of pain do they cause?

1. C afferent fibres - smallest, unmyelinated - cause dull, intense, slow-onset pain
2. Aδ fibres - small, myelinated - cause sharp immediate onset pain


Name two places in the body that do not contain nociceptors?

Brain, liver


What is the bioavailability of morphine administered orally?

50 %


How long does a single dose of morphine last?

3-4 hours


In what form can morphine be administered trans-dermally?

Through fentanyl patches


Name one partial agonist and one antagonist of morphine

Partial agonist = Buprenorphine
Antagonist = Naloxone


How do opioids work?

Opioids bind to opioid receptors in the brain (G protein coupled receptors) and then inhibit the release of pain transmitters at the spinal cord and midbrain. Descending inhibition of pain.


What was the first opioid receptor identified?

µ - receptor (MOP)


Why aren't kappa agonists used?

Caused depression rather than euphoria


What is potency?

Whether a drug is 'strong' or 'weak' relating to how well the drug binds to a receptor


What is efficacy? And what does it relate to?

Maximal response or not? Depends whether is a full or partial agonist


What is tolerance?

Down regulation of receptors with prolonged use. Need of higher doses to achieve same effect


What is dependence?

Psychological craving


How long after the last opioid dose does it take for withdrawal symptoms to set in?

Within 24 hours. Will last 72 hours


Give 5 potential side effects of opioids

1. Respiratory depression
2. Sedation
3. Itching
4. Nausea and vomiting
5. Constipation
6. Immune suppression
7. Endocrine effects


How would you administer Naloxone to a heroin overdose patient and why?

Give ampule IM and then IV. Has a short half life so if they wake up and walk away, will have a reserve, so don't fall back into toxic levels

Titrate to effect - 1ml in 10 ml saline


Why is codeine not given to breast feeding mothers/ paeds?

Codeine is a pro-drug, it needs to be metabolised by cytochrome CYP2D6 and this enzyme is overactive in 5% of the population, so will be at increased risk of respiratory depression with codeine


What property does norpethidine have if it is not excreted?



What is tramadol and what will it interact with?

Weak opioid agonist and prodrug. Also works as a serotonin reuptake inhibitor and nor-epinephrine reuptake inhibitor. Reacts with SSRI's, tricyclic antidepressants and MAOI's