Pain Flashcards
What is the mechanism of action of paracetamol?
- Activation of descending serotonergic (inhibitory) pathways possibly via 5HT3 receptor activation.
- Inhibits reuptake of endogenous endocannabinoids, which increases activation of cannabinoid receptors -> activation of descending, inhibitory pathways.
- Mild inhibition of peroxidases -> analgesic + anti-pyretic
Is paracetamol also an anti-inflammatory?
No -> perioxidases (which is seen in large scale in inflammation) overcome paracetamol and so it loses it effect.
What can a paracetamol overdose cause?
Liver damage
What some the symptoms of paracetamol poisoning?
- Nausea and vomiting early features of poisoning (settle in 24h).
- Onset of right subcostal pain after 24h indicates hepatic necrosis.
Name some strong opioids.
- morphine
- fentanyl
- heroin
Name some weak opioids.
- codeine
- tramadol
Describe the mechanism of action of opioids.
Depressant drug
- Binds to opioid receptor and leads to decreased perception or increased tolerance to pain.
Opioids have an anti-tussive effect. What does this mean?
They suppress coughing due to decreased activation of afferent nerves relaying cough stimulus from airways to brain
What to opioids bind to?
opioid receptor (mu kappa delta)
What are the side effects of opioids?
- nausea & vomiting
- constipation
Why do opioids cause constipation?
activation of opioid receptors in GI tract can reduce gut motility
What can be used to treat constipation?
Laxatives
Name a laxative.
lactulose
What is lactulose?
a non-absorbable disaccharide
Describe lactulose’s mechanism of action.
- Lactulose reaches the large bowel unchanged -> this causes water retention via osmosis and makes it easier to pass stool.
- It can also be metabolised by colonic bacteria. The colonic metabolism of sugars has an additional laxative effect.
