Laxatives

Laxatives are medicines that help resolve constipation or empty the bowel of fecal matter before procedures or surgery involving the lower bowel. There are several different types available (see differences below) and each type works in a particular way. Some soften or loosen up the stool, while others increase how frequently the large colon contracts which helps move the stool along the bowel.

Laxatives may also be called cathartics or purgatives.

What are laxatives used for?

Laxatives are used to treat constipation if lifestyle changes have failed to resolve the constipation or if the person has a medical condition (such as angina) that may be exacerbated by straining.

Before taking a laxative it is important to be sure the person is actually constipated and that the constipation is not due to an underlying, undiagnosed condition. People's bowel habits vary and it does not mean that somebody is constipated if they do not pass a bowel motion every day. Constipation is usually defined as "The passage of hard stools less frequently than the person's normal bowel pattern". Laxatives should generally not be used long-term unless under medical supervision because they can cause electrolyte disturbances (such as low potassium levels), dehydration, and contribute to a sluggish bowel.

Before using a laxative, lifestyle changes, such as drinking more fluid, exercising, and increasing the amount of vegetables and fiber in the diet should be tried first.

Types of laxatives include:

• Bulk-forming laxatives (such as fiber, psyllium, or polycarbophil). These absorb water in the bowel and swell to bulk out the stool making it softer and easier to pass
• Emollient stool softeners (such as docusate). These moisten and lubricate the stool making it easier to pass
• Osmotic laxatives (such as lactulose, and magnesium sulfate/hydroxide) draw fluid into the bowel and soften stools
• Stimulant laxatives (such as senna or bisacodyl) promote contraction of the intestines, promoting the movement of stools through the bowel.

Bowel cleansing preparations

Bowel cleansing preparations are not treatments for constipation. They are used before bowel surgery, colonoscopy, or radiological examinations to ensure that the bowel is free of solid contents.

They should be used with caution in people with fluid and electrolyte disturbances, such as dehydration and low potassium levels. These should be corrected before administration.

Examples of bowel cleansing preparations include:

• citric acid/magnesium oxide/sodium picosulfate
• magnesium sulfate/potassium sulfate/sodium sulfate
• polyethylene glycol-3350 with or without electrolytes 
• sodium biphosphate/sodium phosphate.