Constipation can mean different things to different people. Some people think they are constipated if they do not have their bowels opened every day. Other people only have their bowels opened two or three times a week and they consider this to be normal for them. In a way, being ‘normal’ is what you are used to and any deviation from that may be called constipation. If you are passing hard, small stools and having your bowels opened less frequently than is normal for you, you are constipated. The important thing about having your bowels opened is that it should be painless and not require too much straining and it should be satisfyingly complete.

Causes

Constipation may be a symptom of an underlying disease of the bowel or anus, of the nerves supplying the bowel (e.g. spinal cord injury), or of some other generalized disease such as an underactive thyroid gland (hypothyroidism). In these cases the treatment of the constipation is to treat the underlying disease. Constipation may also be due to general debility, lack of mobility, old age or mental deficiency. However, constipation is most often caused by a diet that does not have sufficient fibre in it and poor bowel habits (not going when you feel the urge).

Drugs may cause constipation, particularly in the elderly. Often there is a combination of factors that come together; for example, an elderly patient with poor bowel actions on a diet low in fibre is prescribed a drug which has a side effect of causing constipation.

Warning You should always seek medical advice for any change in your bowel habits that goes on for more than a week or two, particularly if there is blood in your motions.

Drugs used to treat constipation

Drugs used to treat constipation are usually termed laxatives. Other names include cathartic, purgative, aperient and evacuant. We usually talk about a laxative when we wish to produce a soft, formed, easy to pass motion and a purgative when we wish to produce a fairly quick and fluid emptying of the bowels. However, the terms all mean the same thing and the results will depend on the type of laxative used and its dose.

There are four main groups of drugs used to treat constipation, which may be taken by mouth, and according to how they work they are referred to as stimulant laxatives, bulk-forming laxatives, osmotic laxatives and faecal softeners. Some may also be taken as suppositories or enemas.

Stimulant laxatives

These laxatives increase the movements of the large bowel by ‘irritating’ the lining and stimulating nerves in the bowel wall, which cause the muscles to contract. They may also increase the production of chemicals (e.g. prostaglandins) by cells in the bowel wall, which stimulates the secretion of water and salts into the bowel. How they actually produce these effects is not known but the result is that they speed up bowel movement and reduce the absorption of water and salts, which makes the motions soft and watery and also more bulky.

Harmful effects

All stimulant laxatives may cause intestinal cramps and griping pains, increased secretion of mucus and, in some people, excessive loss of water and salts (particularly potassium). Regular use may cause loss of protein and failure to absorb essential elements from food such as vitamins, which may be harmful, especially in elderly people. In addition, they may cause a weakening of the muscles of the bowel (atony of the colon) so that it does not function properly. This may actually cause constipation and the danger then is that the individual takes further doses of the stimulant laxative which only makes things worse.

Commonly used stimulant laxatives

Bisacodyl may cause intestinal cramps and, when taken by suppository, may produce soreness and irritation. To avoid irritating the lining of the stomach, bisacodyl tablets have a special protective coating (enteric coating) which does not dissolve until the tablets reach the intestine. It is structurally related to phenolphthalein (see later).

Cascara, senna and danthron are chemically related (they are anthraquinones). When they are taken by mouth, soluble breakdown products are absorbed from the small intestine into the bloodstream and excreted back into the bowel (colon) where they stimulate nerves in the bowel which cause the muscles to contract and speed up bowel movement. An acid breakdown product from these laxatives colours the urine red or brown according to how acid the urine is (brown if acid, red if alkaline). If taken over long periods of time, they produce brown patches of pigmentation on the lining of the bowel. This is not serious and clears up in 4-12 months after the drug has been stopped. They should not be used if you are breast feeding. Danthron may irritate the skin in incontinent people.

It has been known for some time that danthron and related drugs (anthraquinones) could possibly cause cancer because they have been shown to be mutagenic (i.e. they can damage the genes) and there is a relationship between this ability and the ability to produce cancer. Long-term use of high daily doses of danthron has been associated with the development of cancer in the intestines and livers of rodents. Even though there is no evidence that danthron causes cancer in humans, this once widely prescribed stimulant laxative is now reserved for treating constipation caused by morphine and related drugs used to treat pain in terminally ill patients.

A combined preparation of danthron and docusate (co-danthrusate, Normax) is available for this purpose. Docusate sodium is a weak laxative which softens the motions and also causes some stimulation of the bowel wall. Danthron combined with a faecal softener, poloxamer 188 is also available (co-danthramer).

Phenolphthalein is a stimulant laxative which, when taken by mouth, is absorbed from the small intestine into the bloodstream where it is taken to the liver and excreted in the bile. This means that phenolphthalein re-enters the intestine and produces a prolonged action on the intestine. After absorption into the bloodstream it is also excreted into the urine which, if alkaline, the phenolphthalein will colour red. Phenolphthalein also colours the motions red. This can be a bit alarming to the individual who may think he is passing blood in his urine and motions. Phenolphthalein may occasionally cause allergic skin rashes, protein to appear in the urine (albuminuria) and damage the red blood cells (haemoglobinaemia).

Sodium picosulphate is a powerful stimulant laxative which is used to empty the bowel before surgery or X-ray examination of the bowel.

Use of stimulant laxatives

Stimulant laxatives should be used only occasionally and only for a dose or two. Except in the terminally or seriously ill, they should never be taken on a regular daily basis. They should not be used to treat children or pregnant woman. They take 6-18 hours to work when taken by mouth.

Powerful stimulant laxatives should not be used: they include aloes, aloin, buckthorn, cassia pulp, colocynth, croton oil, euonymus, ipomoea, jalap, kaladana, podophyllum, rhubarb, tamarind and turpeth, and unstandardized preparations of cascara, frangula, rhubarb and senna.

Castor oil

Castor oil differs from other stimulant laxatives in that it is broken down in the small intestine to ricinoleic acid which causes an increase in fluid secretion from the lining of the small intestine and may possibly act as a direct irritant to the lining of the intestine. Castor oil causes the irritant contents of the intestine to move on rapidly, producing watery motions in about 3-6 hours. Because it works on the small intestine its prolonged use may result in excessive loss of nutrients, fluids and salts. It should not be used.

Bulk-forming laxatives

These are indigestible substances that increase the bulk of the contents of the bowel by absorbing water and swelling. This stimulates the bowel muscles to contract. They also encourage the growth of micro-organisms in the bowel, which increases the bulk. They are taken by mouth.

Many bulk-forming laxatives (see later) are obtained from plants (e.g. seeds, husks, and gums) and some are manufactured (e.g. methylcellulose and related compounds). Bran is a useful bulk laxative and if taken regularly every day helps to keep the bowel movements regular.

Bulk-forming laxatives are the laxatives of choice because they are not absorbed into the bloodstream and they do not interfere with the absorption of nutrients. They are slow to work and may take up to 2-3 days in some people. The choice of bulk-forming laxatives does not really matter so long as the recommended dose is taken with a full glass of water (about 240ml).

Risks of bulk-forming laxatives

Bulk-forming laxatives must be taken with plenty of fluids because of the risk of causing a blockage in the bowels. This is a particular danger in the elderly, in people who are debilitated from a severe illness and in people who have a disease of the bowel. Bulk laxatives may cause wind and distension of the abdomen. Some individuals may be allergic to sterculia and gum preparations, and develop a skin rash and symptoms of hayfever and asthma.

Course bran works better than fine bran because it retains more water, but it can interfere with the absorption of calcium, zinc and iron. Fine bran can be taken in cereals, bread or biscuits. Because of the risk of constipation, bran should not be used by the old elderly, the terminally ill or people with nerve disorders affecting the bowel (e.g. spinal injury). Bran should not be used by individuals with coeliac disease.

Warnings on the use of bulk laxatives

Adequate fluids must be taken each day in order to prevent obstruction to the bowel. They are not suitable for people on a restricted fluid intake and they should be used with caution by anyone taking ‘water tablets’ (diuretics). Bulk laxatives should not be used by individuals with weakened bowel muscles (atony) nor if there is evidence of some narrowing of the bowel. In particular, they should not be used by elderly people who have a blockage of the bowels (faecal impaction) because they will only make the blockage worse. Inhalation of the dry powder from some bulk laxatives may cause wheezing in some patients.

Osmotic laxatives (saline laxatives, health salts)

Osmotic laxatives are salts of magnesium, sodium and potassium in varying mixtures. They cause large amounts of water to be retained in the intestine instead of being absorbed. This increases the bulk of the contents and stimulates the stretch reflexes in the bowel wall. This triggers movement and the passage of a large volume of watery motions. They work in about 2 hours. Because they may produce dehydration due to excessive loss of water, they should be taken with plenty of fluids.

Osmotic laxatives should be used only occasionally as a one-off treatment for constipation.

Lactulose is a complex synthetic sugar compound made up of fructose and galactose. It is not digested in the small intestine and enters the large bowel unchanged. Here bacteria break it down into two weak acids (lactic and acetic) which draw water into the bowel by osmosis and increase the bulk of the bowel contents. The acids also encourage the growth of bacteria, which also adds to the bulk of the contents. The weak acids are absorbed in the upper colon, so the osmotic effect does not continue right through the colon. The increase in bulk of the contents stimulates bowel movements. Because it makes the contents more acid it discourages the growth of those bacteria which produce ammonia and it is therefore also of use in treating people suffering from liver failure. It takes up to 48 hours to work, and may produce nausea and vomiting.

Risk of osmotic laxatives

Osmotic laxatives may produce severe loss of water and cause dehydration which may be harmful in children, in the elderly and in people who are debilitated by illness. Those that contain magnesium salts may be harmful because some magnesium may be absorbed into the bloodstream. In an individual with kidney disease, excretion in the urine may be defective and magnesium may accumulate in the body to produce magnesium poisoning. Sodium is easily absorbed into the bloodstream from those saline laxatives that contain sodium. This may be harmful to people with a raised blood pressure or heart failure and interfere with diuretic treatment aimed at reducing the body’s sodium and water content. They may also cause sodium and water retention in some individuals.

Faecal softeners

There are two types of softeners: lubricants, which cover the faeces in oil and prevent them losing water so that they remain soft and easy to pass (e.g. liquid paraffin); andwetting agents, which make water and solids mix more easily and make faeces soft (e.g. docusate sodium [dioctyl sodium sulphosuccinate], poloxamers).

Liquid paraffin, if used regularly, may decrease the absorption of fat-soluble vitamins A, D, E and K from the intestine. The impaired absorption of vitamin D may decrease the absorption of calcium and phosphates and affect bone formation, and the defective absorption of vitamin K may be harmful in pregnant women. People taking anti-coagulants (anti-blood-clotting drugs) that block the production of vitamin K should not take liquid paraffin because it interferes with the absorption of vitamin K from the intestine and may therefore increase the harmful effects of these drugs.

Young and elderly and debilitated people may, rarely, inhale a few drops of liquid paraffin into their lungs when they swallow it and this may cause pneumonia (lipoid pneumonia). Small amounts may be absorbed from the intestine and may collect in lymph glands, producing swollen lymph glands in the intestinal wall, liver and spleen. It may also leak from the anus, causing irritation (pruritus ani). It should not be used in children under 3 years of age or in people with a swallowing difficulty. It should only be used occasionally.

Wetting drugs used to soften the faeces

Drugs that make water and fatty substances mix more easily (wetting agents) soften the motions and help top lubricate the lining of the bowel. They take 24-48 hours to work. This softening allows more fluid to remain in the mixture. Examples of wetting drugs are docusate sodium and poloxamer. They are often combined with a stimulant laxative (see earlier).

Faecal softeners are of no use in treating long-standing constipation, especially in elderly or debilitated people. They may be useful for short-term treatment, for example in patients who have undergone surgical removal of haemorrhoids or other surgery around the anus.

Misuse of laxatives

Laxatives have been and still are widely misused and abused. They have become part of our folk medicine, and few adults have escaped being ‘purged’ in their lives, and there still is a widely held belief, particularly among elderly people, that a good ‘clear out’ is beneficial. This is strengthened by another belief that, to be healthy, everyone should have their bowels opened at least once every day. Of course none of this is true but around it have developed an extremely lucrative drug industry and herbal industry. Millions of euro are made each year from people emptying their bowels and belching quite unnecessarily.

Warning Do not use stimulant laxatives, osmotic laxatives or faecal softeners on a regular basis. The occasional use of a laxative is not harmful to health but the regular long-term use of stimulant laxatives, osmotic laxatives or faecal softeners may be harmful. Furthermore, the regular use of these laxatives interferes with an individual’s ability to have his or her bowels opened naturally without drugs, no matter what the manufacturers say about the ‘natural’ and ‘gentle’ effects of their laxative products!

The laxative habit – laxative abuse

It is important for you to remember that stimulant and osmotic laxatives empty the bowel; and it is not surprising therefore that someone who has taken a stimulant or osmotic laxative every day for a week or so and then stops the laxative may go for several days without a motion. Unfortunately, this may persuade the individual that he or she cannot ‘go’ and so they take another dose of laxative, and a vicious circle is set up leading to what is called laxative abuse.

The abuse of stimulant and osmotic laxatives is still widespread despite the fact that they cause all kinds of problems to their users – such as irritation of the lining of the bowel; excessive loss of water, nutrients and salts producing tiredness, weakness and thirst; and loss of calcium leading to bone softening.

Poor diet

We in the western world have not been helped in our bowel habits by diets that lack roughage. These diets have contributed to constipation and bowel disorders. Therefore, the sensible treatment of constipation is not to take laxatives but to make sure that your diet contains sufficient roughage e.g. insoluble fibre (cereal fibre) to prevent bowel problems developing. Insoluble fibre has two useful properties: it reaches the bowel without having been digested so that it forms roughage; and, while there, it absorbs fluid, making the motions bulky and stimulating bowel movements. However, it is not necessary to go over the top and shovel spoonfuls of bran on to everything you eat. It is the old story of moderation – eat a good sensible diet which includes adequate fruit, vegetables and cereals (e.g. wholemeal bread). This will provide adequate fibre and help prevent constipation and bowel disease.

When to treat constipation

Constipation may be distressing for some people – such as the elderly and the seriously ill (e.g. dying from cancer) – who may have to take constipating drugs such as morphine for pain. In these individuals the use of laxatives may reduce distress. Any treatment for constipation in such people needs to be tailored to the individual’s needs. This will require knowledge of available preparations and how they work.

Stopping the laxative habit

You should never take a stimulant laxative or an osmotic laxative regularly. These laxatives should be used only occasionally when an individual who is normally not constipated becomes constipated because of some outside factor such as going on holiday. Even then it is better to try a bulk laxative (e.g. bran) and plenty of fluids before resorting to a stimulant or osmotic laxative.

If you are in the habit of taking a stimulant or osmotic laxative regularly, you should take steps to stop it. Try switching to a faecal softener such as docusate sodium (Dioctyl). You should stop your laxative and start with a large dose of Dioctyl; as you settle down to regular bowel movements you should gradually reduce the dose of Dioctyl over a period of several weeks and then stop it. It will help if you drink more fluids than normal each day during the first few weeks. At the same time you should make sure that your diet contains adequate fibre. If you still have a problem, it may be necessary to take a bulk laxative regularly every day (e.g. bran). If you can’t take bran, try something like cellulose (methylcellulose). The latter procedure should be followed if you are in the habit of taking a faecal softener (e.g. Dioctyl) regularly every day.

NOTE You must check with your doctor whether any of the drugs you are taking may cause constipation. If they can, you should decide jointly whether you really need to be taking them, or whether you can switch to a drug or drugs that do not constipate. If either of these actions is not possible, ask your doctor to prescribe a laxative but try to avoid using a stimulant laxative or osmotic laxative if possible (see above).

Faecal Impaction

Poor and irregular bowel movements cause incomplete emptying of the rectum, which may, over time, cause a mass of faeces to block the rectum – faecal impaction. It may occur in children who have defective nervous control of their rectum, in some severely mentally ill or mentally handicapped people and in the elderly, particularly if they are debilitated or confined to bed. Liquid faeces above the obstruction start to dam up and this can distend the bowel. Some of the liquid faeces may seep round the obstruction and start to leak out of the anus; this may be mistaken for diarrhoea and treated with anti-diarrhoeal drugs, which only make the condition worse. It is referred to as spurious diarrhoea. The faecal mass may also cause an ulcer at the site of the impaction.

Faecal impaction is not that uncommon in elderly people and that is why an elderly person who complains of ‘leakage’ should be examined most carefully by a doctor, who will need to examine the inside of the rectum by putting a finger up the anus where mass may be felt. Sometimes the obstruction is higher up and can be felt only by pressing a hand on the abdomen.

Treatment

The treatment of faecal impaction involves the use of a suppository or an enema, and/or manual removal of the impacted mass of faeces by the patient or a doctor or nurse using gloves fingers or a special spoon.

Prevention of any further impaction is essential. Therefore, it is important to try to avoid the use of any drug that may cause constipation, and to take a bulk laxative (e.g. bran) regularly every day along with adequate fluids by mouth.

Drugs that may cause constipation

Many drugs may cause constipation and can produce particular problems in elderly people, who are prone to develop constipation anyway, and in debilitated patients. Drugs that may cause constipation include:

aluminium and calcium antacids in indigestion remedies
anticholinergic drugs
anti-parkinsonim drugs (e.g. bromocriptine)
anti-psychotic drugs
benzodiazepine anti-anxiety drugs and sleeping drugs
beta blockers may occasionally cause constipation or diarrhoea
calcium channel blockers (e.g. verapamil)
ganglion blocking drugs used to treat raised blood pressure (e.g. mecamylamine and pempidine)
iron salts
narcotic pain relievers (e.g. codeine, dextropropoxyphene, morphine, etc.)
tricyclic anti-depressant drugs
thiazide diuretics

Enemas and suppositories

Enemas

Enemas are frequently used in order to apply a laxative directly into the rectum. They include the following.

Salts (e.g. phosphates) draw water from the wall of the bowel into the contents. This increases the bulk of the motions, which stretches the bowel wall and stimulates it to empty. They are used to prepare the bowel for surgery and x-ray. They should not be used regularly because they can disturb the water and salt content of the body.

Oils (e.g. arachis oil, glycerol) lubricate hard faeces and make them easier to pass.

Softeners (e.g. docusate sodium) soften hard faeces and make them easier to pass. Docusate sodium may also have some stimulant effect.

Stimulants (e.g. bisacodyl) irritate the bowel wall and make it contract.

Soaps (e.g. soft soap enema) irritate the bowel wall and may be harmful; they should not be used.

Suppositories

Suppositories offer another method of applying a laxative directly into the rectum. They may include glycerol (a lubricant laxative) or bisacodyl (a stimulant laxative) or sodium acid phosphate (an osmotic laxative).

Health salts

Andrew’s liver salts contains citric acid, sodium bicarbonate, magnesium sulphate and 40% sugar. Other salts that are used as laxatives include purified cream of tartar (potassium acid citrate), Epsom salts (magnesium sulphate), Milk of Magnesia (magnesium hydroxide).

So-called health salts usually contain sodium bicarbonate (bicarbonate of soda) which gives off carbon dioxide when it mixes with the acid in the stomach; this makes you belch. They also contain magnesium and/or sodium or potassium salts which cause water to be retained in the bowel. This increases the bulk of your motions and makes you open your bowels. To put it more plainly, health salts ‘give’ you wind so that you can belch and/or increase the bulk of your motions so that you have to empty your bowels. What belching and unnecessary bowel openings have to do with health is not obvious but some people seem to want to buy ‘health ‘ in a bottle – no matter whether they belch it out at one end or pass it out at the other!