Laxatives can help you empty your bowels if you're constipated. Before taking laxatives you need to be sure that you really are constipated. Normal bowel movements vary from person to person.

If you have cancer, you should always check with your doctor or nurse before taking any type of laxative.

You might not be able to take some types of laxatives if you have a bag on your tummy (a colostomy or ileostomy) to collect your poo. Your doctor or nurse will want to assess your constipation and the cause of your constipation before recommending treatment for you.

Remember – if you have constipation and vomiting, don't take laxatives without checking with your doctor or nurse first. Constipation and vomiting can be a sign of a blocked bowel in some people. Laxatives can cause harm if your bowel is blocked.

How you take them

You can buy many laxatives over the counter without a prescription. Other types of laxatives need a doctor’s prescription.

Laxatives come as:

  • tablets, capsules or granules
  • foods, such as bran
  • syrups
  • powders that can be made into a drink by adding water or fruit juice
  • an enema that you have into the back passage (rectum)
  • suppositories that you have into the back passage

Types of laxative

There are several types of laxatives. Each work in a different way.

Bulk forming laxatives

These work by swelling up inside your bowel. They help to soften and increase the amount of poo. This encourages your bowels to move and push the poo out. This type of laxative can take a few days to work properly. Examples include:

  • Methylcellulose
  • Fybogel
  • Sterculia

Stimulant laxatives

These work by speeding up bowel movement. They can take between 8 and 12 hours to work. Examples include:

  • bisacodyl
  • glycerol suppositiories
  • senna (Senakot)
  • syrup of figs
  • co-danthrusate (Normax) and co-danthramer

Surfactant laxative (stool softener)

These work by softening the poo (stool) by drawing more water and fat into the poo. Examples include:

  • docusate sodium
  • arachis oil enema

Osmotic laxatives

These work by drawing more water into your bowel. This makes your poo softer and easier to pass. Examples include:

  • lactulose syrup
  • macrogols (Movicol and Idrolax)
  • magnesium salts (Andrews liver salts, Epsom salts, Cream of magnesia)
  • phosphate enemas
  • sodium citrate (Microlette and Microlax enemas)

Opioid receptor blockers

People having opioid type painkillers often have constipation. Drugs such as methylnatrexone (Relistor) and naloxegol (Moventig) can help. It reduces constipation in people having opioid painkillers when other laxatives have not worked.

Side effects of laxatives

Different laxatives have different side effects. 

Bulk forming laxatives can cause wind and a swollen tummy (abdomen). They can also block up your bowel. To prevent this you need to drink plenty of water.

Other types of laxatives can cause stomach cramps and wind, and large doses can cause diarrhoea.

The side effects usually go away once your bowels have opened. But let your doctor or nurse know straight away if you continue to have cramping or abdominal swelling, or if you get diarrhoea.

Taking herbal supplements for constipation

Some herbal medicines claim to be laxatives that can help relieve constipation. Some are safe and do work. But we don’t know exactly how some of these medicines will react with your particular cancer treatments. 

Herbal products aren't necessarily all safe. Although they are natural products and you can buy them over the counter at a health shop, some might be harmful to take alongside cancer treatment. So it is very important to let your doctor know if you are planning to take any herbal medicine alongside your cancer treatment.

Last reviewed: 
08 Aug 2019
  • Constipation - Clinical Knowledge Summary 
    National Institute for Health and Care Excellence (NICE), 2016

  • Laxatives or methylnaltrexone for the management of constipation in palliative care patients
    B Candy and others.
    Cochrane Database Syst Rev. 2011 Volume 1

  • Diagnosis, assessment and management of constipation in advanced cancer: ESMO Clinical Practice Guidelines

    P.J Larkin and others

    Annals of Oncology, 2018. Vol 29, Supplement 4.

  • Electronic Medicines Compendium
    Accessed August 2019

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