Laxatives, stimulant

Key examples

• Senna
• Bisacodyl
• Glycerol suppositories
• Docusate sodium

 

Common indications

• Constipation.
• As suppositories for faecal impaction.

 

Mechanisms of action

• Stimulant (also known as irritant or contact) laxatives increase water and electrolyte secretion from the colonic mucosa, thereby increasing volume of colonic content and stimulating peristalsis. They also have a direct pro-peristaltic action, although the exact mechanism differs between agents. For example, bacterial metabolism of senna in the intestine produces metabolites that have a direct action on the enteric nervous system, stimulating peristalsis. Rectal administration of stimulant laxatives, such as glycerol suppositories, provokes a similar but more localised effect and can be useful to treat faecal impaction. Docusate sodium has both stimulant and faecal softening actions.

 

Important adverse effects

• 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).

 

Warnings

• 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.

 

Important interactions

• There are no clinically significant adverse drug interactions with stimulant laxatives.