Laxatives

Question 1

What is the MOA of bulk-forming laxatives?

Answer 1

Retaining fluids within the stool and iincreasing faecal mass, therefore stimmulating peristalsis + stool softening

E.g. Methylcellulose, Physillium jusk, Polycarbophil

Question 2

Name examples of bulk-forming laxatives

Answer 2

E.g. Methylcellulose,
Physillium husk
Polycarbophil

Question 3

What are side-effects of bulk-forming laxatives

Answer 3

• Bloating (due to fermentation)
• Diarrhoea
• Worsening constipation (if patient does not drink enough water or slow transit disorder or defacatory disorder)

Methylcellulose,
Physillium husk

Question 4

What are advanatages and indications of Bulk-forming laxatives?

Answer 4

• First line in chronic constipation after lifestyle changes

Take 2-3 days to work

Methylcellulose,
Physillium husk

Question 5

What are the main disadvanatages and side-effects of bulk-forming laxatives?

Answer 5

Take 2-3 days to work so not for acute constipation + need to drink water with it

Worsening constipation + contraindicated if

• slow transit disorders
• defactory disorders

Other side-effects

• bloating (due to fermenntation)
• diarrhoea

Physillium husk

Methylcellulose,

Question 6

What is the MOA of osmotic laxatives?

Answer 6

Increase osmotic pressure and draws water into the intestinal lumen –> stimmulation of intestinal motility (peristalsis)

E.g. Lactulose
Macrogol
polyethylene glycol

Question 7

Name 3 examples of Osmotic Laxatives

Answer 7

Macrogol
polyethylene glycol
Lactulose

Question 8

What are advanatages and indications of osmotic laxatives?

Answer 8

2nd line in chronic constipation (or in addition to bulk forming)
(Macrogol first line, then lactulose 2nd line)

Also take 2-3 days to work

• Macrogol is licenced for used in faecal imparction

Are also used as bowel prep before Endoscopy

Question 9

What are the disadvantages and side-effects of osmotic diuretics?

Answer 9

Take 2-3 days to work

Side effects

• Diarrhoea (especially lactulose if lactose intolerant)
• Dehydration
• Flatulence, bloating
• Electrolyte abnnormalities (if magnesium salts are used)

Question 10

What is the MOA of stimmulant laxatives?

Answer 10

Stimulation of epithelial cell secreation of electrolytes into colonic lumen

1. increased secretion of fluid into the colon
2. Myneteric neuronal depolarisation –> colonic contractions –> peristalsis

Senna
Bisacodyl and sodium picosulfate

Question 11

Name some stimmulant laxatives

Answer 11

Bisacodyl and sodium picosulfate (colonic + rectal nerves)
Senna (colonic nerves)
(Docusate is emulsification with mild stimmulant activity)

Question 12

What are the advanatages and indications for stimmulant laxatives

Answer 12

Take 6-12 h to work

• after bulk-formin and osmotic if stools are soft but difficult to pass, or there is a sensation of inadequate emptying
• Quicker than other forms of laxatives

Question 13

What are the side-effects of stimmulant laxatives?

Answer 13

• Diarrhoea
• Senna: Melanosis coli (benign hyperpigmentation of colon)

Question 14

What is the management of opioid-associated constipation?

Answer 14

Do not prescribe bulk-forming laxatives.

Offer an osmotic laxative and a stimulant laxative (or docusate is an alternative which also has stool-softening properties)

Question 15

What is the aim of laxative treatment and when should it be reduced?

Answer 15

Gradually titrate the laxative dose(s) up or down aiming to produce soft, formed stool without straining at least three times per week.