Stimulant laxatives

Question 1

Give the 2 main clinical indications for the use of stimulant laxatives.

Answer 1

1) Constipation.

2) As suppositories for faecal impaction.

Question 2

Name the P-drugs that are stimulant laxatives.

Answer 2

1) bisacodyl
2) dantron
3) docusate sodium
4) senna
5) sodium picosulphate

Question 3

What is the action of stimulant laxatives?

Answer 3

Increase water and electrolyte secretion from the colonic mucosa, thereby increasing volume of colonic content and stimulating peristalsis.

Question 4

How does Senna stimulate a peristaltic action?

Answer 4

Bacterial metabolism of Senna in the intestine produces metabolites that have a direct action on the enteric nervous system and this stimulates peristalsis.

Question 5

1) Which administration technique for stimulant laxatives can be useful for treatment of faecal impaction?
2) What are the 2 actions of decussate sodium?

Answer 5

1) Rectal administration (E.G. glycol suppositories) as they have a similar but localised pro-peristaltic effect to Senna.
2) Both stimulant and faecal softening actions.

Question 6

Give 3 reasons as to why stimulant laxatives might need to be avoided.

Answer 6

1) Patients with intestinal obstruction as there is a risk this could induce perforation.
2) Haemorrhoids
3) Anal fissure

Question 7

1) Describe how you should treat constipation with stimulant laxatives.
2) Describe how you should treat faecal impaction with stimulant laxatives.

Answer 7

1) Regular administration, twice a day. Dose is variable (1-2 tablets of Senna twice daily). Titrate to effect.
2) rectal stimulant laxatives, once only or PRN with a maximum of 1 per 24 hours. For example, glycerol suppositories.

Question 8

1) When might you consider prescribing a stimulant laxative to prevent constipation?
2) Name 3 faecal softeners.

Answer 8

1) When prescribing opioid analgesics to be taken regularly, consider co-prescription of a laxative to prevent constipation.
2) arachis oil, co-danthrusate and docusate sodium