Laxatives

Laxatives are a type of medicine that can help you empty your bowels if you are having trouble going to the toilet.

They are widely used to treat constipation if lifestyle changes (see below) haven't helped. They are available over-the-counter, without a prescription, from pharmacies and supermarkets.

Types of laxatives

The main laxatives used in the UK are:

• bulk-forming laxatives, such as ispaghula husk and methylcellulose, which work in the same way as dietary fibre – they increase the bulk of your stools (faeces) by helping your stools retain fluid, encouraging your bowels to push the stools out
• osmotic laxatives, such as lactulose and polyethylene glycol, which make your stools softer and easier to pass by increasing the amount of water in your bowels
• stimulant laxatives, such as bisacodyl, senna and sodium picosulfate, which speed up the movement of your bowels by stimulating the nerves that control the muscles lining your digestive tract
• stool softener laxatives, such as arachis oil and docusate sodium, which increase the fluid content of hard, dry stools, making them easier to pass

There are also a number of alternative laxatives that are less commonly used, including bowel cleansing solutions, peripheral opioid-receptor antagonists, linaclotide and prucalopride.

Which laxative should I use?

Although laxatives have been around for a long time, there is a lack of high-quality evidence about exactly how effective they are and whether certain laxatives are better than others.

Unless there is a reason why specific laxatives may be more suitable than others (see below), most adults should try using a bulk-forming laxative first. These usually start to work after about two or three days.

If your stools remain hard, try using an osmotic laxative in addition to – or instead of – a bulk-forming laxative. If your stools are soft, but you still find them difficult to pass, try taking a stimulant laxative in addition to a bulk-forming laxative.

Osmotic laxatives usually start to work after about 2 or 3 days, while stimulant laxatives usually have an effect within 6 to 12 hours.

If you are unsure which laxative you should take, speak to your GP or pharmacist for advice. You should also see your GP if you are still constipated after trying all of these types of laxative, or if you think your child might benefit from taking laxatives.

Things to consider

Although laxatives are available over-the-counter, this does not mean they are suitable for everyone.

Laxatives are not usually recommended for children, unless advised by a doctor, and some types of laxatives may not be safe to use if you have certain conditions, such as Crohn’s disease or ulcerative colitis.

Before using laxatives, you should carefully read the patient information leaflet that comes with the medication, to make sure it is safe for you to take.

Read more about the considerations regarding laxatives.

How to take laxatives

How you take laxative medication depends on the form it comes in. Laxatives are commonly available as:

• tablets or capsules you swallow
• sachets of powder you mix with water and then drink
• suppositories – a capsule you place inside your back passage (rectum), where it will dissolve
• liquids or gels that you place directly into your rectum

Some laxatives are also designed to be taken at certain parts of the day – such as first thing in the morning or last thing at night.

Make sure you carefully read the patient information leaflet that comes with your medication, so you know how to take it properly. If you are not sure how to take your medication, ask your pharmacist for advice.

While you are taking bulk-forming or osmotic laxatives, it is particularly important to stay well hydrated by drinking plenty of fluids. This is because these laxatives can cause dehydration.

Never take more that the recommended dose of laxatives, as this can be harmful and can cause troublesome side effects (see below).

How long should laxatives be used for?

Ideally, laxatives should only be used occasionally and for short periods of time. You should stop taking a laxative when your constipation improves.

After taking a laxative, you can help stop constipation returning by making certain lifestyle changes, such as drinking plenty of water, exercising regularly and including more fibre in your diet. Measures such as this are a better way of preventing constipation than excessive use of laxatives.

See your GP for advice if you are often constipated, despite making appropriate lifestyle changes, or if your constipation hasn't improved after taking laxatives for more than a week.

Do not get into the habit of taking laxatives every day to ease your constipation, because this can be harmful.

In some cases, you may be prescribed a laxative to use regularly, but this should always be supervised by your GP or a gastroenterologist (a specialist in digestive conditions).

Possible side effects

Like most medications, laxatives can cause side effects. These are usually mild and should pass once you stop taking the medication.

The specific side effects you may experience depend on the exact medication you are taking, but common side effects of most laxatives include:

• bloating
• passing wind (flatulence)
• painful tummy (abdominal) cramps
• feeling sick
• dehydration – which can make you feel lightheaded, experience headaches and pass urine that is a darker colour than normal

Contact your GP for advice if you experience any particularly troublesome or persistent symptoms while taking laxatives.

Excessive or prolonged use of laxatives can also cause diarrhoea, intestinal obstruction (where the bowel becomes blocked by large, dry stools) and unbalanced levels of salts and minerals in your body.

For more information about the side effects related to your medication, check the patient information leaflet that came with it or look up your medicine in the Medicines A-Z.

Alternatives

It is often possible to improve constipation without having to use laxatives. Before trying laxatives, it may help to make a number of lifestyle changes, such as:

• increasing your daily intake of fibre – you should eat at least 18-30g of fibre a day; high-fibre foods include fruit, vegetables and cereals
• adding bulking agents, such as wheat bran, to your diet – these will help make your stools softer and easier to pass, although bran and fibre can sometimes make bloating worse
• drinking plenty of water
• exercising regularly

Read more about preventing constipation.