Fibres and Laxatives

Laxatives are a type of medicine that help you to move your bowels. There are several different types and each one has a different effect on your digestive system.


For general advice on diet for those suffering from constipation click here.

If changing to a more natural diet without processed foods is not sufficient, natural fibres can be added to help your bowels work more effectively.

Psyllium or Ispaghula husk (which also comes in the commercially available form of Fybogel, Metamucil, Volcolon and Regulan) is a very effective natural ‘bulk-forming laxative’. It is not absorbed by the small intestine. It can help reduce the symptoms of both constipation and mild diarrhoea because the fibre absorbs water and softens the stool to a gel-like consistency.

Golden linseed has been used as far back in time as ancient Egypt to alleviate poor digestion. Linseed is an excellent source of dietary fibre. It is also rich in lignin, which can help reduce cholesterol levels and helps protect the mucous membranes. Linseed can be used safely over long periods without side effects.

1-2 tablespoons a day taken with plenty of water will ensure a generous supply of dietary fibre. Another option is to soak them overnight. You can then add them to your usual cereal or fruit juice.

About 50% of people with constipation see significant improvement when using natural fibre in their diet. The effect takes a few weeks to become fully apparent, so be patient, and remember that sufficient water intake (1.5-2 ltrs per day, as long as you don’t have a medical condition that prevents this) is essential. Also, it is important not to be overzealous with fibre supplements. It is better to start with a low dose and increase over a few days. In severe slow-transit constipation or in constipation caused by opioids, fibre supplements might worsen symptoms. Please consult your doctor if you have any queries.


If your bowels do not respond well enough to natural fibres you may be prescribed an ‘osmotic laxative’. Osmotic laxatives work by increasing the amount of fluid in your bowels. This softens your stools and helps to stimulate your body to pass them more easily.

Sorbitol is an osmotic laxative that is found in many diet/light drinks and food products, and also in plums, prunes, dried fruits, apple and apple juice.

Lactulose is a syrup that is metabolised by the bacteria in your large bowel. This over-the-counter medication can lead to excessive gas production.

Movicol and Laxido are the most commonly prescribed osmotic laxatives. They are similar drugs that are made by different companies. They contain a substance called ‘macrogol’ (polyethylene glycol). Macrogols are large molecules which pass through the body without being absorbed by the gut. They hold on to water and prevent it being absorbed, and this extra water in the gut keeps the motions soft and prevents constipation. They also contain small amounts of salts to prevent dehydration and salt deprivation.

These medicines are often favoured because:

  • They tend to cause less bloating than other laxatives.
  • Patients do not tend to become tolerant to them, so once you have found an effective dose, this same dose will usually remain effective over the longer term.
  • Generally, they are very safe and have very few risks and interactions. However, patients with certain bowel diseases may not be able to take them, and there is some indication that they may affect the efficacy of certain prescription drugs, e.g anti-epileptics. Always read the patient information leaflet which comes with the medication and consult your doctor for further information.

Movicol and Laxido usually come in sachet form and water needs to be added to them according to the manufacturers’ instructions supplied with them. They are also available in syrup form which can be added to water. How you take this medicine depends on the problem that you are taking it for:

  • For the treatment of constipation: you need to establish a regimen of Movicol/ Laxido that gives you regular, soft bowel motions. Follow the instructions given by your doctor, then increase or decrease the dose until you find the lowest effective, regular dose that controls your symptoms. It is not essential that you open your bowels every day – the aim of these laxatives is to prevent the stools from being hard, making it easier to empty your bowel and to reduce tummy pain. In general it is better to take it regularly to avoid constipation rather than erratically to treat it.
  • For use after anal surgery: we often prescribe Movicol or Laxido after surgery. If you have had a bottom operation, such as haemorrhoid, fissure or fistula surgery, it can be uncomfortable to open you bowels immediately after surgery. These laxatives help keep the stool consistency soft and minimise this discomfort.
  • For use after laparoscopic rectopexy: we usually recommend a laxative to minimise straining after surgery as there is a small risk that doing so might damage the surgical repair before it has healed. When your bowels start to work, which may not be for four or five days after surgery, you may find that they are overactive. In such circumstances, you should reduce the Movicol/ Laxido to maintain soft, regular stools. Your surgeon will usually have given you guidance as to how long to continue with the laxatives.


If your stools are soft but you still have difficulty passing them, you may be prescribed a stimulant laxative such as Bisacodyl or Senna/Sennakot.

These laxatives stimulate the muscles that line your digestive tract, helping them to move stools and waste products along your large intestine to your anus. Unfortunately your bowels may get used to stimulant laxatives, so they lose their effect and eventually even high doses will become ineffective. Therefore these types of laxatives should only be used occasionally (not more then 2-3 doses weekly).


Prucalopride (Resolor) is a laxative that acts directly on the nervous system of the gastrointestinal tract.

This drug is expensive, and your doctor will only prescribe it if you have failed to achieve adequate relief from a course of at least two laxatives from different laxative classes, taken at the highest tolerated recommended dose for at least six months. In addition, you should have had tests to confirm slow transit constipation and exclude other important causes of constipation.

About 30% of patients respond well to his medication. If the effects are not apparent after four weeks, there is no benefit to continuing the medication. Many patients suffer side-effects of headache, diarrhoea, nausea and abdominal cramps in the first 7-10 days of treatment but these usually resolve within two weeks.

Lubiprostone is a so-called chloride channel activator. If treatment with lubiprostone is not effective after two weeks the benefit of continuing treatment should be reconsidered.


If you have only experienced constipation for a short time, your GP will normally advise you to stop taking the laxative once your stools are soft and easily passed.

If you have constipation due to a medicine or an underlying medical condition you may have to take laxatives for much longer, possibly many months or even years.

Please be advised that the information on this website is not a substitute for professional medical advice, diagnosis or treatment