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Laxatives

Published by Bupa's health information team, September 2009.

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

Laxatives are medicines that relieve constipation (difficulty with bowel movements). They are a popular type of over-the-counter remedy.

Why would I take laxatives?

Your doctor 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 the anus (anal fissure)

Laxatives can also be helpful for people with constipation caused by prescription medicines (eg codeine) or by illness and in older people who are constipated because of reduced mobility. They are also prescribed to clear the bowels before surgery or for colonoscopy, a test for looking inside the large bowel.

Changes in bowel movements can sometimes indicate more serious conditions. If you are losing weight or you notice blood in your faeces, visit your GP for advice.

What are the main types of laxative?

Laxatives are medicines that work on the bowel to relieve constipation. There are several types of laxative that you can buy without a prescription. The main ones 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

There are also faecal softeners such as arachis oil and liquid paraffin available.

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 isphagula 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.

How to take laxatives

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

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

You should generally try a bulk-forming laxative (eg bran) first. Then move on to try an osmotic laxative if this doesn't work. It's best to only take the stimulant laxatives if you have already tried changing your diet (eg eating more fibre and drinking enough) and the other types of laxatives, and these have not worked.

Bulk-forming laxatives usually come as powders or granules that you have to 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 does not build up in your bowel and cause a blockage. They can take several days to work.

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 (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. You should start with a low dose and build up gradually until you feel comfortable when you have a bowel movement.

Generally, you should only use laxatives for short periods of time or only use them occasionally, for example, no more than twice in one week for senna. Once your bowel movements are back to normal, you should keep them regular by eating a balanced diet with plenty of fluids and fibre. Some people need to use laxatives for a longer time, for example, if they take certain medicines such as opioids (eg codeine, morphine), iron supplements, or antacids containing calcium, which can cause constipation. Your doctor 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 doctor or pharmacist before taking a laxative if:

  • you are pregnant or breastfeeding
  • you 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. 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. Rarely, they can block the intestine.

Osmotic laxatives can cause wind, cramps and discomfort in the 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.

Interactions of laxatives with other medicines

Check with your doctor 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.

Generic names Examples of common brand names

Bulk-forming laxatives

bran

ispaghula husk

Fibrelief, Fybogel, Isogel, Ispagel Orange, Regulan

methylcellulose

Celevac

sterculia

Normacol, Normacol Plus

Osmotic laxatives

lactulose

Duphalac, Lactugal, Regulose

macrogols

Laxido, Movicol, Movical-Half

magnesium salts

Milk/cream of Magnesia, Epsom Salts, Original Andrews Salts

phosphates

Carbalax, Fleet enema, Fletchers' Phosphate Enema

sodium citrate

Microlette, Micralax, Relaxit

Stimulant laxatives

bisacodyl

Dulco-lax tablets and suppositories

co-danthramer

Codalax, Danlax, Codalax Forte

co-danthrusate (with ducosate sodium)

Normax

docusate sodium

Dioctyl, Docusol, Norgalax Micro-enema (enema)

glycerol

Glycerin suppositories

senna

Manevac, Senokot

sodium picosulfate

Dulcolax Liquid, Dulcolax Perles

Related topics

Further information

Sources

  • Joint Formulary Committee. British National Formulary. 57th ed. London: British Medical Association and the Royal Pharmaceutical Society of Great Britain, 2009: 59-63
  • Simon C, Everitt H, Kendrick T. Oxford handbook of general practice. 2nd ed. Oxford: Oxford University Press, 2005: 472

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: September 2009

 

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