Laxatives

Question 1

Example of a laxative

Answer 1

Senna

Question 2

How does senna work?

Answer 2

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

Bacterial metabolism of senna in the intestine produces metabolites that have a direct action on the enteric nervous system, stimulating peristalsis.

Question 3

Indications of senna

Answer 3

Constipation

Question 4

Contraindications of senna

Answer 4

Stimulant laxatives should not be used in patients in whom intestinal obstruction is suspected as there is a risk that this could induce perforation.

Rectal preparations are usually avoided if haemorrhoids or anal fissure are present.

Question 5

Side effects of senna

Answer 5

Abdominal pain or cramping may occur with stimulant laxative use and diarrhoea is an obvious potential adverse effect.

With prolonged use, some stimulant laxatives cause melanosis coli (reversible pigmentation of the intestinal wall).

Question 6

Possible interactions of senna

Answer 6

No clinically significant adverse drug interactions

Question 7

Elimination of senna

Answer 7

Eliminated in faeces via biliary excretion and/or in urine

Question 8

Patient information for senna

Answer 8

1–2 tablets of senna twice daily.

Explain that you are offering treatment with a laxative that will help stool to pass.Good oral fluid intake will also help; 6–8 glasses of liquid per day.

Stimulant laxatives do not work immediately and they may need a few doses before a sustained effect is noticed.

If they are regularly passing more than two or three soft stools per day, the dose should be reduced/stopped.

Mention that side effects such as abdominal cramps and flatulence can occur, but these may get better over time.