Laxatives

Medications used to treat constipation are called laxatives

Treatment with a laxative is needed only if lifestyle measures, such as eating plenty of fibre, drinking enough fluid, and exercising regularly do not work well in relieving constipation.

Talk to your doctor or pharmacist if you think you need a laxative. Read more about constipation.
Note: the information below is for laxative use in adults. For information about the safe use of laxatives in children, see laxatives (children).  

What are the different types of laxatives?

There are several types of laxatives that differ in how quickly they start working, how helpful they are in different situations, their taste and cost and possible side effects. Some of them are available from your pharmacy, and others on prescription from your doctor. The four main groups of laxatives are:

More-detailed information about these four types of laxatives, including common brand names, is provided in the table at the bottom of this page.

There are different forms of laxatives. Some can be taken by mouth; others such as an enema inserted in the bottom.

  • Tablets, capsules, syrups, drops and powders are taken by mouth, and depending on the type of laxative, can take hours or days to work.
  • Rectal laxatives (enemas or suppositories) are inserted into the rectum (bottom). These are usually effective within minutes to an hour and are mainly used as a last resort to treat severe constipation.

How to use laxatives safely

Drink plenty of water:
  • When taking laxatives, you should try to drink at least 8 to 10 cups of water a day.
  • This is because laxatives, especially an osmotic laxative, can make you dehydrated.
  • If you take a bulk-forming laxative and you do not drink enough fluid this can cause a blockage in the gut as the poos may become dry and difficult to pass.
Use laxatives only for short periods of time:
  • Long-term use can make your body dependent on them, so your bowel no longer works normally without them. 
  • Generally, it is recommended that you do not take laxatives for more than 5 to 7 days in a row.
  • If you still have constipation after taking laxatives for several days contact your doctor for advice.

Possible side effects

Like all medicines, laxatives can cause side effects, although not everybody gets them. The common side effects of laxatives are stomach pain or cramps, bloating, gas in the tummy, flatulence or 'farting'. Other side effects include:

  • Constipation: ongoing use of laxatives can cause constipation because the bowel loses muscle and nerve response and can no longer move poos out. This results in dependency on the laxative, so that higher doses are needed to poo.
  • Diarrhoea and dehydration: taking too much of some laxatives can lead to diarrhoea and losing too much salt from the body. 
Laxatives do NOT help with weight loss
Many people believe that using laxatives can help with weight loss. This is not true – by the time laxatives act on the large intestine, most foods and calories have already been absorbed by the small intestine. Any weight that is lost is from the water you excrete through runny poos and the results are only temporary. Instead, this can lead to dangerous side effects like dehydration, electrolyte imbalance and possibly even dependence.

More-detailed information on laxative types

Always ask your doctor or pharmacist which laxative is best for you.

  • Usually, treatment with a bulk-forming laxative is tried first.
  • If poos remain hard then an osmotic laxative may be tried, or used with a bulk-forming laxative.
  • If bowel movements are soft but you still find them difficult to pass then a stimulant laxative may be tried.
  • In cases of severe constipation (impaction), high doses of the osmotic laxatives may be used.

The different types of laxatives are detailed in the table below.

Bulk-forming laxatives (or fibre supplements)

Bulk-forming laxatives are high in fibre which adds bulk to the poos. The bulky size stimulates the bowel muscles, causing poos to move along, leading to an easier bowel movement. 

  • They usually take 2 to 3 days to cause a bowel movement.
  • Bulk-forming laxatives may be useful in people with haemorrhoids, anal fissure, chronic diarrhoea associated with diverticular disease and irritable bowel syndrome. 
  • They are not recommended for constipation caused by opioids, or in people unable to maintain adequate fluid intake, at risk of dehydration or with problems swallowing.
  • It's important to drink enough fluids when using bulk-forming laxatives - not drinking enough fluids can cause blockage of the gut. 
Examples include:
  • unprocessed bran or oat bran
  • psyllium (Konsyl D®, Mucilax®, Metamucil®, Bonvit®)
  • sterculia (Normacol®, Normafibe®)
Read more about bulk-forming laxatives.

Stimulant laxatives

  • Stimulant laxatives stimulate the nerves in the bowel, causing muscle contractions and in this way gets the bowel moving.
  • The tablets or capsules usually cause a bowel movement after 8 to 12 hours. A bedtime dose is recommended, so you are likely to feel the urge to go to the toilet sometime the next morning. 
  • The rectal stimulant laxatives (suppositories or enemas) are quick acting and cause a bowel movement after 15 minutes but may take up to 1 hour. 
  • Stimulant laxatives are used for constipation caused by opioids or when complete emptying of the bowel is required such as before surgery (operation).
Examples include:
  • Tablets:
    • bisacodyl (Dulcolax tablet)
    • sennoside B (Senokot tablet).
  • Suppositories:
    • bisacodyl (Dulcolax suppository, Lax-Suppositories®)
    • gylcerol suppositories.

Osmotic laxatives

  • Osmotic laxatives draw water into the bowel. The bowel becomes filled (distended) with extra fluid, and this stimulates the muscles of the walls of the bowels to contract and squeeze the bowel movement along.
  • The oral liquids usually take 1 to 3 days to cause a bowel motion.
  • The rectal osmotic laxatives (enema) usually cause a bowel motion within 30 minutes.
Examples include:
  • Syrup:
    • lactulose (Laevolac).
  • Powder (to be mixed with water):
    • Movicol
    • Lax-Sachets
    • Molaxole.
  • Enema:
    • Fleet enema
    • Micolette enema
    • Microlax enema.

Faecal or stool softeners

  • These laxatives soften the poos.
  • The oral softeners usually cause a bowel movement after 12 to 72 hours.
  • The rectal softeners (enema) usually cause a bowel motion within 30 minutes.
Examples include:
  • Tablets and drops:
    • docusate (Laxofast capsule, Coloxyl tablet)
    • Coloxyl drops.
  • Enema:
    • docusate (Coloxyl enema).

Learn more

New Zealand Formulary Patient Information

References

Laxatives New Zealand Formulary

Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 16 May 2019