Laxatives

Published by Bupa's Health Information Team, October 2011.

This factsheet is for people who would like information about taking laxatives.

Laxatives are medicines that relieve constipation (a condition where bowel movements occur less often than usual, or are difficult or painful).

Why would I take laxatives?

Your GP or pharmacist may advise you to take laxatives if you have constipation, especially if you have another condition that could get worse if you strain during bowel movements, for example:

• angina
• piles (haemorrhoids)
• a painful tear in the skin round your anus (anal fissure)

Laxatives can also be helpful if you have constipation caused by prescription medicines (eg codeine) or by an illness. Older people who are constipated because of reduced mobility may also be advised to take laxatives.

Laxatives are also prescribed to clear the bowels before surgery or for colonoscopy, a test that allows a doctor to look inside your large bowel.

Changes in your bowel movements can sometimes be caused by problems other than constipation. If you’re losing weight or you notice blood in your faeces, see your GP for advice.

What are the main types of laxative?

There are several types of laxative that you can buy without a prescription. The main types are:

• bulk-forming laxatives, such as wheat bran and ispaghula husk
• osmotic laxatives, such as lactulose and macrogols
• stimulant laxatives, such as senna and glycerol suppositories
• faecal softener laxatives, such as arachis oil and liquid paraffin

How do laxatives work?

Each type of laxative works in a different way to help relieve or prevent constipation.

• Bulk-forming laxatives work by increasing the amount of faeces you have and softening them - the fibre in the bran or ispaghula husk 'bulks out' the faeces. This then encourages your bowels to move and push the faeces out.
• Osmotic laxatives work by increasing the amount of water that stays in your faeces as they pass through your large bowel. This makes them softer and easier to pass.
• Stimulant laxatives work by speeding up the movements of your intestines.
• Faecal softener laxatives work by lubricating and softening the faeces, which makes them easier to pass.

How to take laxatives

You can buy each of the four basic types of laxatives without a prescription.

Bulk-forming laxatives are good for people who have small, hard faeces. You should only use them if you can't increase the amount of natural fibre you eat. They are also useful for people with a colostomy or ileostomy bag, irritable bowel syndrome, piles (haemorrhoids) or an anal fissure. They may take a few days to start working.

You should generally try a bulk-forming laxative (eg bran) first. Then move onto an osmotic laxative if this doesn't work. Only take stimulant laxatives if you have already tried changing your diet (eg eating more fibre and drinking plenty of fluids) and the other types of laxatives haven’t worked.

The different types of laxatives come in various forms.

• Bulk-forming laxatives usually come as powders or granules that you add water to. It's important to drink enough fluids and always follow the instructions that come with the medicine, so that the extra bulk doesn’t build up in your bowel and cause a blockage.
• Osmotic laxatives come as powders, liquids or enemas (a liquid that you inject into your back passage). The osmotic laxative lactulose can take 48 hours to work. Make sure you drink enough fluids while taking these medicines – osmotic laxatives can have a dehydrating effect because they draw fluid from your body into your bowel.
• Stimulant laxatives come as tablets, suppositories (a medicine that is inserted into your back passage), capsules, liquids and enemas. Stimulant laxatives, such as senna, work within eight to 12 hours, so you should take them at night for an effect the next morning. Start with a low dose and build up gradually until you feel comfortable when you have a bowel movement.
• Faecal softener laxatives come as capsules or enemas.

Generally, you should only use laxatives for short periods of time or only use them occasionally. This is because it’s thought that the longer you take laxatives, the more your body may become dependent on them and your bowel may not function normally without them. Taking laxatives for too long can also lead to diarrhoea, dehydration and unbalanced levels of salts and minerals in your body. Once your bowel movements are back to normal, aim to keep them regular by eating a balanced diet with enough fluids and fibre.

Some people need to use laxatives for a longer time, for example, if you take certain medicines such as opioids (eg codeine or morphine), iron supplements, or antacids containing calcium, which can cause constipation. Your GP will advise you about this.

You shouldn't give laxatives to children unless your doctor has prescribed them.

Always read the patient information leaflet that comes with your medicine, and if you have any questions, ask your pharmacist for advice.
 

Special care

Check with your GP or pharmacist before taking a laxative if:

• you’re pregnant or breastfeeding
• ou know that your kidneys or liver aren't working properly
• you have an inflammatory bowel disease such as ulcerative colitis

Side-effects of laxatives

This section doesn't include every possible side-effect of laxatives. Please read the patient information leaflet that comes with your medicine for more information.

• Common side-effects with the bulk-forming laxatives are wind and a swollen abdomen (tummy). Rarely, they can block your bowel.
• Osmotic laxatives can cause wind, cramps and discomfort in your abdomen. You may also become dehydrated.
• Stimulant laxatives can cause stomach pains and cramping, and too large a dose can cause diarrhoea. If you use a suppository, the skin around your anus can become irritated.
• Faecal softener laxatives can cause can cause cramps in your abdomen, nausea and irritation in your anal area if you use them for a long time.

Interactions of laxatives with other medicines

Check with your GP or pharmacist before you take any other medicines or herbal remedies at the same time as a laxative.

Names of common laxatives

The main types of laxatives are shown in the table.

All medicines have a generic name. Many medicines also have one or more brand name. Generic names are normally written in lower case, whereas brand names start with a capital letter.

There are many different products marketed for constipation. Some have more than one ingredient, or different ingredients sold under the same brand name. Ask your pharmacist for advice.
 

For answers to frequently asked questions on this topic, see Common questions .

For sources and links to further information, see Resources .