Motility of GI tract

Question 1

List 4 anti-emetic drugs and describe their MOA

Answer 1

[receptor below are receptor in the vomiting pathway; blocking the receptors would prevent vomiting]

1. Dimenhydrinate: H1 receptor antagonist
2. Hyoscine: muscarinic receptor antagonist
3. Ondansetron: 5HT3 receptor antagonist
4. Domperidone: dopamine receptor antagonist

Question 2

List 2 prokinetic drugs and describe their MOA

Answer 2

IPAN: Intrinsic primary efferent nerves that increase peristalsis

1. Cisapride: 5HT4 receptor agonist; (5HT4 stimulates IPAN)
2. Domperidone: Dopamine inhibits IPAN; MOA: D2 receptor antagonist

Question 3

List 4 laxatives and describe their MOA

Answer 3

1. Methlycellulose: bulk laxative that increases fecal mass and stimulate peristalsis
2. Lactulose: osmotic laxative that increase amount of fluid in bowel
3. Glycerol: faecal softener
4. Senna: stimulant laxatives that directly stimulates the myenteric plexus

Question 4

Describe 4 treatment of diarrhoea

Answer 4

1. Oral rehydration therapy: salt, sugar and water
2. Codeine: stimulates opioid receptor that in turn decreases peristalsis of the gut
3. Kaolin: adsorbents that claim to bind to toxin and bacteria
4. Hyoscine: antispasmodic drugs, muscarinic receptor antagonist

Question 5

Describe the treatment for irritable bowel syndrome

Answer 5

IBS is an idiopathic chronic disorder and can cause both diarrhoea and constipation-> treat using the diarrhoea/constipation drugs
-Ondansetron: inhibits EPAN (responsible for nausea, vomiting and abdominal pain)