Constipation and the Use of Laxatives

(3/15/12)- As we have written elsewhere, constipation is a common reason for primary care visits and referrals to gastroenterologists.

The problem with the concept of constipation lies with the fact that prevalence varies with the definition of constipation. A standard definition can be found in the Rome III criteria for chronic constipation.

In order to meet the criteria, it is necessary to have two or more of the following:

Straining during at least 25% of bowel movement.
Lumpy or hard stools at least 25% of bowel movement.
Sensation of incomplete evacuations for at least 25% of bowel movement.
Sensation of anorectal blocking for at least 25% of bowel movement.
Manual maneuvers to facilitate at least 25% o f bowel movement.
Fewer than 3 bowel movements each week.

One should also note that loose stools are rarely present without use of laxatives

The criteria further indicate that these symptoms must have been present for at least three months, with symptom onset at least six months before diagnosis

Before undertaking prescription measures, use of sufficient fiber in the diet is recommended. Fiber should be accompanied by adequate water intake. Too much fiber can result in bloating and flatulence without relieving symptoms. This treatment should be accompanied by an active lifestyle with stress on physical activity

Drug treatment for constipation falls into 4 categories according to their method of action: Analgesics (NSAID's); Anticholinergics (antihistamines, antidepressants, antispasmodics, antipsychotics); Neurally active drugs (antihypertensives, ganglion blockers, vinca alkaloids, thalidomide, calcium channel blockers, 5HT3 analgesics); Iron supplements (antacids containing aluminum).

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(12/28/02)-Constipation is a common medical condition, the incidence of which increases with age. It is one of those conditions that people do not like to talk about and is only reported to physicians when it becomes extremely painful. Yet a private confidential survey, The National Health Interview Survey, indicated that 4 ˝ million people said they are constipated most of the year. It is considered the most common gastrointestinal disorder in the United States, resulting in about 2 million annual visits to physicians. Most people resort to over-the-counter laxatives for relief of constipation, as reflected in annual sales of $725 million of these laxatives. There are an estimated 700 or more commercially available laxatives and enema preparations.

There are many people who think they are constipated, when in fact their bowel movements may be regular. The myth is that a bowel movement should take place every day. Miss a day and this means you are constipated. There is no right number of daily or weekly bowel movements, nor is there a standard for consistency of the stool. Some people naturally have firm stools and may only have movements three times a week. Many research studies in the past used different definitions of constipation and this may account for the variation in these studies.

The Principles of Ambulatory Medicine, 3rd edition states…"there is a wide variation in the frequency of bowel movements among normal subjects of both sexes and of all ages, ranging from three times per day to three times per week. Therefore, someone who has fewer than three bowel movements per week is constipated by definition. On the other hand, a change in frequency of movements from, say, two per day to three per week may also signify constipation…. Even one movement per week is acceptable if it does not represent a recent change in bowel frequency and is not associated with symptoms such as pain on defecating or bloating."

Presently, a generally accepted definition of constipation involves the passage of small amounts of hard, dry bowel movements, usually fewer than three times a week. The bowel movement is usually difficult and painful, with the individual feeling bloated, uncomfortable and sluggish. It is most probable that most people get constipated at one time or another due to poor diet, and lack of exercise. In most cases constipation is temporary and not serious. Again, according to The Principles of Ambulatory Medicine, 3rd Edition, "The mechanism of action for most laxatives is poorly understood, and the potential for toxicity is often underestimated. Few data are available for comparison among the various laxatives, and the decision to use a particular laxative often is determined by individual preference rather than by objective evidence of efficacy or safety."

The following information is taken from The National Digestive Diseases Information Clearinghouse (NDDIC), a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S. Department of Health and Human Services. Established in 1980, the clearinghouse provides information about digestive diseases to people with digestive disorders and to their families, health care professionals, and the public.

"To better understand constipation it is helpful to know something about how the colon (the large intestine) works. As food moves through it, the colon absorbs water while forming waste products, or stool. Muscle contractions in the colon push the stool toward the rectum. By the time stool reaches the rectum, it is solid because most of the water has been absorbed.

"The hard and dry stools of constipation occur when the colon absorbs too much water. This happens because the colon's muscle contractions are slow or sluggish, causing the stool to move through the colon too slowly. Below is a list of the most common causes of constipation:

"The most common cause of constipation is a diet low in fiber found in vegetables, fruits, and whole grains and high in fats found in cheese, eggs, and meats. People who eat plenty of high-fiber foods are less likely to become constipated.

"Fiber--soluble and insoluble--is the part of fruits, vegetables, and grains that the body cannot digest. Soluble fiber dissolves easily in water and takes on a soft, gel-like texture in the intestines. Insoluble fiber passes almost unchanged through the intestines. The bulk and soft texture of fiber help prevent hard, dry stools that are difficult to pass.

"On average, Americans eat about 5 to 20 grams of fiber daily, short of the 20 to 35 grams recommended by the American Dietetic Association. Both children and adults eat too many refined and processed foods in which the natural fiber is removed.

"A low-fiber diet also plays a key role in constipation among older adults. They often lack interest in eating and may choose fast foods low in fiber. In addition, loss of teeth may force older people to eat soft foods that are processed and low in fiber.

Not Enough Liquids

"Liquids like water and juice add fluid to the colon and bulk to stools, making bowel movements softer and easier to pass. People who have problems with constipation should drink enough of these liquids every day, about eight 8-ounce glasses. Other liquids, like coffee and soft drinks that contain caffeine seem to have a dehydrating effect.

Lack of Exercise

"Lack of exercise can lead to constipation, although doctors do not know precisely why. For example, constipation often occurs after an accident or during an illness when one must stay in bed and cannot exercise.


"Pain medications (especially narcotics), antacids that contain aluminum, antispasmodics, antidepressants, iron supplements, diuretics, and anticonvulsants for epilepsy can slow passage of bowel movements.

Irritable Bowel Syndrome (IBS)

"Some people with IBS, also known as spastic colon, have spasms in the colon that affect bowel movements. Constipation and diarrhea often alternate, and abdominal cramping, gassiness, and bloating are other common complaints. Although IBS can produce lifelong symptoms, it is not a life-threatening condition. It often worsens with stress, but there is no specific cause or anything unusual that the doctor can see in the colon.

Changes in Life or Routine

"During pregnancy, women may be constipated because of hormonal changes or because the heavy uterus compresses the intestine. Aging may also affect bowel regularity because a slower metabolism results in less intestinal activity and muscle tone. In addition, people often become constipated when traveling because their normal diet and daily routines are disrupted.

Abuse of Laxatives

"Myths about constipation have led to a serious abuse of laxatives. This is common among older adults who are preoccupied with having a daily bowel movement.

"Laxatives usually are not necessary and can be habit-forming. The colon begins to rely on laxatives to bring on bowel movements. Over time, laxatives can damage nerve cells in the colon and interfere with the colon's natural ability to contract. For the same reason, regular use of enemas can also lead to a loss of normal bowel function.

Ignoring the Urge to Have a Bowel Movement

"People who ignore the urge to have a bowel movement may eventually stop feeling the urge, which can lead to constipation. Some people delay having a bowel movement because they do not want to use toilets outside the home. Others ignore the urge because of emotional stress or because they are too busy. Children may postpone having a bowel movement because of stressful toilet training or because they do not want to interrupt their play.

Specific Diseases

"Diseases that cause constipation include neurological disorders, metabolic and endocrine disorders, and systemic conditions that affect organ systems. These disorders can slow the movement of stool through the colon, rectum, or anus.


Diseases That Cause Constipation

Neurological disorders that may cause constipation include:

  • Multiple sclerosis
  • Parkinson's disease
  • Chronic idiopathic intestinal pseudo-obstruction
  • Stroke
  • Spinal cord injuries.

Metabolic and endocrine conditions include:

  • Diabetes
  • Underactive or overactive thyroid gland
  • Uremia.

Systemic disorders include:

  • Amyloidosis
  • Lupus
  • Scleroderma.


Problems with the Colon and Rectum

"Intestinal obstruction, scar tissue (adhesions), diverticulosis, tumors, colorectal stricture, Hirschsprung's disease, or cancer can compress, squeeze, or narrow the intestine and rectum and cause constipation.

Problems with Intestinal Function (Chronic Idiopathic Constipation)

"Also known as functional constipation, chronic idiopathic (of unknown origin) constipation is rare. However, some people are chronically constipated and do not respond to standard treatment. This chronic constipation may be related to multiple problems with hormonal control or with nerves and muscles in the colon, rectum, or anus. Functional constipation occurs in both children and adults and is most common in women.

"Colonic inertia and delayed transit are two types of functional constipation caused by decreased muscle activity in the colon. These syndromes may affect the entire colon or may be confined to the left or lower (sigmoid) colon.

"Functional constipation that stems from abnormalities in the structure of the anus and rectum is known as anorectal dysfunction, or anismus. These abnormalities result in an inability to relax the rectal and anal muscles that allow stool to exit."


Laxatives stimulate the action of the gut and are generally mild acting: cathartics have a more dramatic action and lead to a more fluid evacuation. Laxatives used in high doses can have a cathartic effect.

Patients who use laxatives fall into two classes: those who take them habitually and those who abuse them surreptitiously. Habitual users are usually middle-aged or elderly, who have become in the cycle of taking laxatives for a variety of reasons, often related to a poor diet, decreased mobility and wrong perception of normal bowel movements. Surreptitious abusers of laxatives often have related conditions such as anorexia nervosa or bulimia nervosa or Munchausen’s syndrome. These abusers generally believe that increasing intestinal transit will reduce the absorption of nutrients. Other surreptitious abusers are athletes, such as weight lifters or jockeys, who have to fulfill certain limits for body weight before competition.

Laxative classification:

Laxatives are generally classified according to their mode of action. The four main mode of action are:

  1. Bulk forming laxatives including bran, isphagula, psyllum, methylcellulose, plus dextrose (Metamucil) and sterculim
  2. Osmotic laxatives including magnesium salts (Milk of Magnesia), sugar alcohols (sorbitol, mannitol, lactitol), small volume enemas (citrates, phosphates), lactulose, polyethylene glycol.
  3. Stimulant laxatives including surface-active substances (docusates, bile acids), diphenylmethane derivatives (phenolphthalein-Correctal, Ex-Lax), bisacodyl, cascara, aloe, sodium picosulfate, castor oil (Ricinoleic acid), anthraquinones (senna, dantron).
  4. Fecal softeners and lubricants including mineral oil (arachis oil, liquid paraffin), dioctyl sodium (Colace) or sulfosuccinate (Surfak).

The efficacy of all laxatives, with the exception of the docusates, is similar, and the effect is dose-dependent. In sufficiently high dosage many laxatives promote catharsis, which implies purgation and a more liquid stool. The most widely used laxatives are the stimulant preparations: those containing senna, bisacodyl and sodium picosulfate and wheat bran and lactulose.

Adverse effects of laxatives

Laxatives containing psyllium have been associated with anaphylaxis, asthma and other allergic conditions. Other potential adverse effects include increased gas and bloating sensation, and bowel obstruction if stricture present.

Liquid paraffin, the major lubricant laxative, has been associated with lipoid pneumonia as a result of aspiration or the oil. Its use should be avoided in those individuals with a tendency to aspiration or regurgitation and it should also be avoided just before bedtime.

E. coli and other intestinal bacterium split the sennosides, which are the major active ingredients of senna leaf and fruit, to rhein anthron. Rhein anthron is structurally similar to dantron, a laxative well known to be hepatotoxic. It should be noted that rhubarb, a natural laxative, also contains rhein anthron.

Docusates have also been implicated in hepatotoxicity. They are surface-active agents with emulsifying and detergent properties and they act by allowing water to interact with fecal mass resulting in loose stool, as well as probably acting as a softening agent. They also act on the gut mucosa wall, affecting the gastrointestinal and hepatic uptake of other drugs such as erythromycin, increasing the potential hepatotoxicity.

The classical adverse effect of laxatives is diarrhea, which may result in severe metabolic disturbances caused by depletion of electrolytes. Colace (dicotyl sodium) has the potential to result in electrolyte imbalance, which is reversible on stopping the Colace.

Castor oil is often associated with cramping abdominal pain and is usually reserved for bowel preparation before surgical and diagnostic procedures. Liquid paraffin has been associated with anal seepage of oily material. The FDA, because of mutagenic effects in mice, has restricted the synthetic anthranoid dantron. Some advocate its use only in terminally ill patients.

Sodium salts, including Phospho-Soda and Fleet enema can cause dehydration and hyperphosphatemia in chronic renal failure.


Most laxatives are safe when used occasionally, although they can have significant adverse effects. Over-the-counter stimulants laxatives are prone to abuse because of their cheapness and ready availability. Discuss your condition with your primary physician before starting a regimen of laxatives.


Harold Rubin, MS, ABD, CRC, Guest Lecturer
updated March 15, 2012

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