Pain

Question 1

What are 4 drugs for treating pain?

Answer 1

• Paracetamol
• Opioids
• Co-amoxiclav
• Lactulose

Question 2

What are some examples of opioids?

Answer 2

• Weak - codeine, tramadol

- Strong - morphine, fentanyl, heroin

Question 3

What is the mechanism of action for opioids?

Answer 3

• Over-arching mechanism at a cellular level is a depressant effect on cellular activity
• Multiple sites in pain pathway where activation of the opioid receptor leads to decreased perception or increased tolerance to pain
• Anti-tussive effect due to decreased activation of afferent nerves relaying cough stimulus from airways to brain

Question 4

What is the mechanism of action for co-amoxiclav?

Answer 4

Contains:

• Amoxicillin (like all penicillin-like drugs) binds to bacterial penicillin binding proteins which prevents transpeptidation (the cross linking process for bacterial cell wall synthesis)
• Clavulanate is an inhibitor of beta lactamase which is a bacterial enzyme that can degrade beta lactam anti-biotics and thus confer resistance to these antibiotics

Question 5

What is the mechanism of action for lactulose?

Answer 5

• Lactulose is a non-absorbable disaccharide which reaches the large bowel unchanged to cause water retention via osmosis and an easier to pass stool (often prescribed before opioids to prevent constipation)
• It can also be metabolised by colonic bacteria
• No drug target

Question 6

What are some side effects of opioids?

Answer 6

• Nausea & vomiting - increase activity in chemoreceptor trigger zone
• Constipation - opioid receptors in GI tract can reduce gut motility
  - Overdose - respiratory depression (direct and indirect inhibition of respiratory control centre)

Question 7

What are some side effects of co-amoxiclav?

Answer 7

• Well tolerated

- Nausea and diarrhoea

Question 8

What are some side effects of lactulose?

Answer 8

• Abdominal pain
• Diarrhoea - colonic metabolism of sugars has an additional laxative effect
• Flatulence
• Nausea