Laxatives

Question 1

What are the four main groups of laxatives?

Answer 1

Bulk forming, Osmotic, Stimulant, Stool softeners (BOSS).

Question 2

Give some examples of bulk-forming laxatives.

Answer 2

Bran, ispaghula husk, methylcellulose, sterculia.

Question 3

How do bulk-forming laxatives work?

Answer 3

Increase the bulk of the stool, increasing ease of passing.

Question 4

What is the onset of action of bulk-forming laxatives?

Answer 4

72 hours (3 days).

Question 5

What are the side effects of bulk forming laxatives?

Answer 5

Bloating, cramping, flatulence.

Question 6

When are bulk-forming laxatives used?

Answer 6

Colostomy, ileostomy, haemorrhoids, anal fissure, IBS, diverticular disease, ulcerative colitis.

Question 7

Give some examples of osmotic laxatives.

Answer 7

Lactulose and macrogols.

Question 8

How do osmotic laxatives work?

Answer 8

By drawing water from the body into the bowel or retaining water in the bowel.

Question 9

What is the onset of action for osmotic laxatives?

Answer 9

Up to 2 days for max effect.

Question 10

What are the side effects of osmotic laxatives?

Answer 10

Abdominal pain and bloating.

Question 11

Which osmotic laxatives act faster - macrogols or lactulose?

Answer 11

Macrogols.

Question 12

Which fast acting osmotic laxatives are used to quickly clear the bowel?

Answer 12

Phosphate enemas and magnesium salts.

Question 13

Give examples of stimulant laxatives.

Answer 13

Bosacodyl, sodium picosulfate, senna, glycerol, co-danthramer.

Question 14

Which stimulant laxative is only used in the terminally-ill? Why?

Answer 14

Co-danthramer due to its carcinogenicity.

Question 15

How do stimulant laxatives work?

Answer 15

By increasing intestinal motility.

Question 16

What is the onset of action of stimulant laxatives?

Answer 16

8-12 hours - bedtime dose recommended.

Question 17

Which form of stimulant laxatives act the quickest? In how long do they act?

Answer 17

Suppositories. 20-60 minutes.

Question 18

What are the side effects of stimulant laxatives?

Answer 18

Abdominal cramps.

Question 19

Co-danthramer can colour one’s urine. What colour should be expected?

Answer 19

Red.

Question 20

Stimulant laxatives should not be used in which age group unless under the advice of a prescriber?

Answer 20

Children under 12.

Question 21

Give some examples of stool softening laxatives.

Answer 21

Liquid paraffin, docusate sodium (weak stimulant), peanut (arachis) enemas.

Question 22

How do stool softening laxatives work?

Answer 22

Decrease surface tension and increase the penetration of water into the stool. Softens and wets stool.

Question 23

Which laxatives are first line?

Answer 23

Bulk forming (BOS).

Question 24

Which laxatives should be used for opioid induced constipation?

Answer 24

Osmotic or stimulant. NOT bulk forming.

Question 25

Describe the treatment of constipation in pregnant women.

Answer 25

Diet and lifestyle first line. Then bulk forming. Then osmotic. Stimulants can be used but cause abdominal pain and diarrhoea.

Question 26

Describe the treatment of constipation in children.

Answer 26

Diet and lifestyle first. Macrogols are first line treatment, then stimulant if macrogols fail. Can try lactulose.