Pharmacology of pain Flashcards
What are the medications used for pain?
-Opioids
-Co amoxiclav
-Lactulose
-Paracetamol
What are examples of weak opioids?
-Codeine
-Tramadol
What are examples of strong opioids?
-Morphine
-Fentanyl (heroin)
What is the primary mechanism of action of opioids?
-Depressant effect on cellular activity
-Multiple sites in pain pathway that can be activated or deactivated for pain
-Cough suppressant due to decreased activation of afferent nerves relaying cough stimulus to brain
-Suppresses GABA so stimulates descending pathways
What is the drug target of opioids?
Opioid receptors
What are the mild side effects of opioids?
-Nausea
-Vomiting
-Constipation (reduced gut motility)
What does a opioid overdose result in?
-Respiratory depression (direct and indirect inhibition of respiratory system)
-Rhabdomyolysis (damaged muscle tissue releases proteins and electrolytes into blood which can damage kidney and cause renal failure)
How to prevent opioid overdose?
Naloxone
What is the primary mechanism of co-amoxiclav?
-Amoxicillin binds to bacterial penicillin binding proteins and prevents transpeptidation (cross linking process for bacterial wall synthesis)
-Clavulanate is an inhibitor of beta lactamase which is an enzymes which can degrade beta lactams
What is the drug target of co-amoxiclav?
-Amoxiciilin= penicillin binding protein
-Clavulanate= beta lactamase
What are the main side effects of co amoxiclav?
-Nausea
-Diarrhoea
What is the primary mechanism of action of lactulose?
-Non absorbable disaccharide so reaches large bowel unchanged
-Causes water retention via osmosis and makes stools easier to pass
-Metabolised by colonic bacteria so added laxative effect
What are the main side effects of lactulose?
-Abdominal pain
-Nausea
-Diarrhoea
-Flatulence
Why is lactulose started before opioids?
Nullifies the constipation side effect of opioids
What is the pain pathway?
- Receptor detects stimulus
- Impulse travels through peripheral sensory neurones
- Decussates at dorsal horn
- Travels contralaterally
- Thalamus and cerebral cortex
- Descending inhibitory pathways
- Travels to dorsal horn
- Diminishes transfer of signal at dorsal horn
