Unfortunately constipation is a common problem. Most of the time it results by going to the toilet more often than usual to empty the bowels, or passing hard or painful stools. Constipation may be caused by not eating enough fiber, or not drinking enough fluids. It can also be a side-effect of certain medicines, or related to an underlying medical condition. In many cases, the constipation cause is not clear. Laxatives are a group of medicines that can treat constipation. Ideally, laxatives should only be used for short periods of time until symptoms ease. Note: there is a separate leaflet on constipation in children.
Primary constipation is a result of lifestyle factors, such as decreased physical activity and eating habits. Secondary constipation can be due to pathologic changes, such as disease or an intestinal obstruction. Medications may also produce constipation symptoms, also known as drug-induced constipation. A medication class commonly associated with constipation is opioids.
What are the treatments for constipation?
If the lifestyle measures do not work well, treatment with a laxative is needed.
There are four main groups of laxatives that work in different ways:
- Bulk-forming laxatives.
- Stimulant laxatives.
- Osmotic laxatives.
- Faecal softener laxatives.
Sometimes these are known as fiber supplements. These increase the bulk of your stools in a similar way to fiber. They can have some effect within 12-24 hours but their full effect may take several days to develop.
- Unprocessed bran is a cheap fiber supplement. If you take bran, it is best to build up the amount gradually. Start with two teaspoons a day, and double the amount every five days until you reach about about 1-3 tablespoons per day. You can sprinkle bran on breakfast cereals, or mix it with fruit juices, milk, stews, soups, crumbles, pastries, scones, etc.
- Other fiber supplements include ispaghula (psyllium), methylcellulose, sterculia, wheat dextrin, inulin fiber and whole linseeds (soaked in water).
There are also various branded products available that contain the ingredients ispaghula, methylcellulose or sterculia and your pharmacist will be able to advise you as to which may be most suitable for you.
A note of caution: fiber and bulk-forming laxatives partly work by absorbing water (a bit like blotting paper). The combination of bulk-forming laxatives and fluid usually produces soft, bulky stools which should be easy to pass out. When you eat a high-fiber diet or take bulk-forming laxatives:
- You should have plenty to drink. At least two liters per day (8-10 cups). The stools may become dry and difficult to pass if you do not have enough to drink. Very rarely, lots of fibre or bulk-forming laxatives and not enough fluid can cause an obstruction in the gut.
- You may notice an increase in wind (flatulence) and tummy (abdominal) bloating. This is normal and tends to settle down after a few weeks as the gut becomes used to the increase in fibre (or bulk-forming laxative).
Occasionally, bulk-forming laxatives can make symptoms worse if you have very severe constipation. This is because they may cause abdominal bloating and discomfort without doing much to clear a lot of faeces which are stuck further down the gut. See a doctor if you feel that bulk-forming laxatives are making your symptoms worse.
These stimulate the nerves in the large bowel (the colon and rectum, sometimes also called the large intestine). This then causes the muscle in the wall of the large bowel to squeeze harder than usual. This pushes the stools along and out. Their effect is usually within 8-12 hours. A bedtime dose is recommended so you are likely to feel the urge to go to the toilet sometime the following morning. Stimulant laxative suppositories act more quickly (within 20-60 minutes). Possible side-effects from stimulant laxatives include abdominal cramps, and long-term use can lead to a bowel that is less active on its own (without laxatives). This can be thought of as a ‘lazy bowel’.
Stimulant laxatives include bisacodyl, docusate sodium, glycerol, senna and sodium picosulfate. These medicines can be prescribed on a prescription in the unbranded (generic) form. Commercially branded versions (proprietary brands) contain the same ingredients but are generally only available for purchase over-the-counter. Examples include bisacodyl, docusate, senna, ispaghula and sodium picosulfate.
These work by retaining fluid in the large bowel by osmosis (so less fluid is absorbed into the bloodstream from the large bowel). There are two types – lactulose and a group called macrogols (also called polyethylene glycols). Lactulose can be bought over-the-counter and macrogols are available on prescription.
Lactulose can take up to two days to have any effect so it is not suitable for the rapid relief of constipation. Possible side-effects of lactulose include abdominal pain and bloating. Some people find the taste of lactulose unpleasant. Macrogols act much faster and can also be used in high doses to clear faecal loading or impaction. Stronger osmotic laxatives (such as magnesium salts and phosphate enemas) can be used to clear the bowel quickly and in situations such as before bowel surgery.
These work by wetting and softening the faeces. The most commonly used is docusate sodium (which also has a weak stimulant action too). Bulk-forming laxatives also have some faecal-softening properties. peanut (arachis) oil enemas are occasionally used to soften impacted faeces in the rectum. The rectum is the lowest part of the colon, just before the back passage (anus).
Liquid paraffin used to be commonly used as a faecal softener. However, it is now not recommended, as it may cause side-effects, such as seeping from the anus and irritation of the skin, and it can interfere with the absorption of some vitamins from the gut.
Do probiotics work against constipation?
Researchers at King’s College in London scoured the medical literature and found 14 studies that met their criteria for a well-done study. All were clinical trials that randomly assigned people with constipation to take either probiotics or a placebo (or other control treatment).
By pooling the findings of the trials, the researchers found that on average, probiotics slowed “gut transit time” by 12.4 hours, increased the number of weekly bowel movements by 1.3, and helped soften stools, making them easier to pass. Probiotics that contained Bifidobacterium appeared to be the most effective. The study will be published in the October American Journal of Clinical Nutrition.