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Medicines for constipation (adults)

Laxatives are medicines that help you to poo (pass a bowel motion). Different laxatives take different times to work – some work very quickly while others take a few days. Ideally, you should use them for a short time only. Changing what you eat and drink, and becoming more active are the best longer-term treatments for constipation.

There are several groups of laxatives.

Bulk-forming laxatives

constipation-drinkingBulk-forming laxatives are also called bulking agents or fibre supplements. This type of laxative is usually the first one that people try.

Bulking agents work by making your poo softer, which makes it easier to pass. You can get them from your GP on prescription, or you can buy them over-the-counter at a pharmacy. You can also get some at the supermarket. Examples of bulk-forming laxatives include psyllium (Konsyl-D, Metamucil, Mucilax) and sterculia (Normacol).

Using bulk-forming laxatives

It usually takes two to three days for bulk-forming laxatives to have any effect, so make sure you take them according to the manufacturer's directions, or as your GP or pharmacist tells you.

It's important to drink plenty of fluid (at least eight cups a day) if you are taking a bulk-forming laxative as this helps to stop it blocking your digestive system.

While these laxatives help with constipation, some may cause bloating in your abdomen (tummy).

Stimulant laxatives

These stimulate the nerves in your bowel so it squeezes harder and pushes the poo (faeces) out. 

The main problem with stimulant laxatives is that your bowel may stop working normally, and you may become reliant on them. If you need to take them for more than a week or two, talk to your doctor. Examples of stimulant laxatives include senna and bisacodyl

Osmotic laxatives

These work by keeping water in your gut (intestines), and so keeping the poo softer. Sometimes doctors prescribe an osmotic laxative for someone with faecal impaction. Lactulose and macrogols are osmotic laxatives.

Faecal (stool) softener laxatives

These are medicines that you put into your bottom (rectum). They tend to work faster than pills and are good for constipation that is low in your gut. Generally, if you are using these you will also be using another laxative that you swallow. Docusate is a faecal softener laxative.

Natural laxatives

Some foods, such as kiwifruit and prunes, can help to relieve constipation for some people. Try having a couple of kiwifruit or about six prunes a day – if this doesn't help, try having a glass of prune juice or a kiwifruit drink such as Kiwi Crush. These juices are high in sugar, so make sure you clean your teeth after having them.


Just because you can buy some laxatives over the counter does not mean they are safe for all people. If you have any bowel condition, are pregnant or breastfeeding, have liver or kidney problems, or diabetes, it's important that you talk to your GP, practice nurse, or pharmacist before using any laxatives.

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Written by HealthInfo clinical advisers. Endorsed by GP liaison, Gastroenterology, Canterbury DHB. Last reviewed July 2017.


Page reference: 49605

Review key: HICSA-13804