Drugs Affecting GIT Motility

Question 1

What are Purgatives (pro-kinetic agents)

Answer 1

• used to relieve constipation
  Include:
• Laxatives
• Faecal softeners
• Stimulant purgatives

Question 2

What do Laxatives do? what does it promote

Answer 2

form bulky hydrated mass in GIT lumen promoting peristalsis

Question 3

What do osmotic Laxatives do?

Answer 3

• draw water into gut to accelerate transfer of contents through small intestine
• sugars broken down by bacteria GIT creating acidic metabolites which attract water

Question 4

What do stimulant laxatives do?

Answer 4

• increase electrolyte
• increase peristalsis

Question 5

What do Faecal Softeners do?

Answer 5

• act as a surfactant -> reduces water tension which produces softer faeces

Question 6

What do D2 Receptor Antagonists do? Examples?

Answer 6

Examples:
- Domperidone
- Metoclopramide
Action:
- prevent stimulation of D2 receptors that inhibit cholinergic smooth muscle activation
- increase lower oesophageal sphincter pressure and enhances gastric emptying

Question 7

What are treatments for vomiting?

Answer 7

• assess and address cause
• Anti-emetic if appropriate

Question 8

Antimuscarinic (Anti-emetic drugs)? examples? AEs?

Answer 8

Examples:
- Hyoscine, Kwells, Travacalm
Action:
- nonselective, competitive antagonist
AEs:
- blurred vision
- urinary retention

Question 9

Anti-Emetic - Antihistamines (H1 receptor antagonists)? Examples? AEs?

Answer 9

Examples:
- Promethazine
- Diphenhydramine
Action:
- inhibits H1 receptors in area postrema
AEs:
- Blurred vision
- urinary retention
- dry mouth

Question 10

Anti-Emetic - D2 Receptor Antagonists? Examples?

Answer 10

Examples:
- Domperidone
- Metoclopramide
Action:
- facilitates gastric emptying

Question 11

Anti-Emetic - 5HT3 Antagonists? Examples?

Answer 11

Examples:
- Ondasetron
Action:
- Central and peripheral action
- CTZ = main site of action
- 70-80% effectiveness in chemotherapy

Question 12

Summary of Anti-Emetics

Answer 12