Q. I occasionally have a problem with constipation, and fortunately it usually clears up by itself. But if I ever should need to take something for it, what should I take? I’ve noticed all kinds of laxatives, stool softeners and other treatments for constipation at the drug store, but I’m not sure what works best. Also, should I ever be concerned about what’s causing the constipation?

A.Many people have constipation from time to time, and it’s usually not a sign of anything wrong. Every now and then, however, it can be a clue to an underlying problem with your intestines, even something as serious as cancer. So if your constipation is severe or persistent, check with your doctor to make sure nothing serious is going on.

Oddly enough, there’s no universally accepted definition of constipation. For some people, it means moving your bowels less often than usual; for some it means having painful or difficult bowel movements. And for others, it’s both. Even excluding serious problems, there can be many reasons why you’re constipated.

These include being inactive, not drinking enough fluids and not eating enough fiber. You can also develop constipation if you don’t answer nature’s call and avoid going to the bathroom when you first feel the urge. Many medicines can make you constipated.

Ask your doctor whether you should try going off a certain medicine to see if it might be causing the problem. Surprisingly, even laxatives can lead to constipation if you overuse them. “Laxative abuse,” as doctors call it, develops after prolonged use of stimulant-type laxatives: After a while, your bowels become dependent on them. Certain medical problems can lead to constipation.

In fact, constipation might be one of the first clues to an underlying medical disorder, such as an underactive thyroid gland (hypothyroidism), depression or an imbalance of minerals in the body (too much calcium or too little potassium, for example).

Treatment for constipation depends on whether the problem is recent or longstanding, mild or severe. Often you can take care of it with relatively minor dietary and lifestyle changes. Drink plenty of water, up to two quarts a day. Eat plenty of fruits and vegetables. Try some bran cereal for breakfast. Exercise regularly. And be sure to answer nature’s call as soon as possible.

If you need to take medicine for constipation, here’s a rundown on the different types available:

* Mineral salt laxatives, such as milk of magnesia (magnesium hydroxide). These increase the amount of water in the intestines, and increase the pressure within them.

* Stimulant laxatives, such as cascara, senna (Senokot) and bisacodyl (Dulcolax, Correctol). These work by irritating and stimulating the intestines into having a bowel movement. They are the strongest laxatives, and the ones most likely to cause dependence.

* Bulk-producing laxatives, such as psyllium (Metamucil), methylcellulose (Citrucel) and polycarbophil (Fibercon). These work by absorbing water, increasing the size of the stool, and thus increasing the pressure within the intestines to have a bowel movement. They are the safest and most “natural” type of laxative.

* Lubricants, such as mineral oil. These work by retaining water in the stool and softening it. Although mineral oil is an old-time remedy that is often used for chronic constipation in children, it can occasionally get into the lungs and lead to a chemical irritation.

* Detergent laxatives, such as docusate (Colace). These work by making it easier for water to mix with the fats present in stool, thus softening the stool. These laxatives are good when the stool is hard or dry, or when having a bowel movement is painful, such as when hemorrhoids are acting up.

* Lactulose (Chronulac). This works by increasing the water in the stool and softening it.

* Suppositories, such as glycerin or bisacodyl (Dulcolax), work by stimulating the nerves of the rectum to have a bowel movement.

The fastest acting laxatives are the suppositories (which work within minutes), followed by mineral salts (a few hours), then the stimulant laxatives (several hours to overnight). The bulk-forming and detergent laxatives (which are more stool softeners than stimulants), take from one to three days to show results. So for occasional use when you’d like results within hours, try a mineral salt or stimulant laxative.

For a more natural regularity, use a fiber-type, bulk-forming laxative. If your bowel movements are hard or painful, use a detergent laxative (after checking with your doctor to see why they’re painful). But first, see if you can manage the problem without taking any medicine at all. Jay Siwek, chairman of the department of family medicine at Georgetown University Medical Center, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington. Consultation is a health education column and is not a substitute for medical advice from your physician.

Constipation is defined as the difficulty of passing stools, incomplete passage, or infrequent passage of hard stools. It can be further defined as having less than three stools per week for women and five for men despite a high residual diet, or a period greater than 3 d without a bowel movement. It can be caused by gastrointestinal disorders, metabolic and endocrine disorders, pregnancy, neurogenic and psychogenic problems, or it could be drug induced.

Laxative Mechanisms of Action

Laxatives promote bowel evacuation by decreasing water and electrolyte absorption, increasing intraluminal osmolarity, or increasing hydrostatic pressure in the gut. Chronic use of laxatives, particularly stimulants, may lead to laxative dependency. Laxative dependency, in turn, may result in fluid and electrolyte imbalances, steatorrhea, osteomalacia, and vitamin and mineral deficiencies. Known as laxative abuse syndrome (LAS), it is difficult to diagnose. Laxative abuse syndrome is often seen in women with anorexia nervosa, depression, and personality disorders and also in elderly patients with quasimedical concerns about their bowel movements. Table: Properties of Laxatives outlines important properties of six types of laxatives.

Table: Properties of Laxatives

Bulk-Forming Agents

Bulk-forming agents are used to promote regularity and are equally indicated for both constipation and diarrhea. The mechanism of action (MOA) is to provide fiber that is not digested or absorbed. This adds bulk to the stool and retains some water in the lumen of the gastrointestinal tract.

Side effects can include fluid and electrolyte imbalance. Specific drugs and usual dosages are as follows:

1. Methylcellulose (Citrucel ®): 4-6 g/d

2. Polycarbophil (FiberCon ®, Mitrolan ®): 4-6 g/d

3. Psyllium (Fiberall ®, Metamucil ®, Konsyl ®, etc.): Dose varies with product

Stool Softeners/Surfactants

These agents provide detergent activity and facilitate admixture of fat and water to soften stool. They also will retain water in the lumen of the gastrointestinal tract. They do not add volume to the stool, but they do prevent hardening of the stool and may prevent pain on defecation. They may be used postoperatively to decrease discomfort caused by defecation and for patients with heart disease to prevent Valsalva’s maneuver efforts upon defecation, which can produce cardiac arrhythmias. Commonly used stool softeners and surfactants include docusate sodium (Colace ®, Doxinate ®), 50-360 mg/d; docusate calcium (Surfak ®), 50-360 mg/d; and docusate potassium (Dialose ®, Diocto-K ®, Kasof ®, etc.), 100-300 m/d.

Saline Cathartics

These agents attract and retain water in intestinal lumen, increasing intraluminal pressure and cholecystokinin release. These drugs contain an anion or cation that is poorly absorbed and remains in the lumen of the gastrointestinal tract. In an effort to maintain equal osmotic pressure on both sides of the cell membranes of the gastrointestinal tract, water will be secreted and not resorbed within the lumen. Agents and their dosages include magnesium citrate (Citrate of Magnesia ®, Citroma ®), 4 oz to 1 full bottle 120-300 mL; magnesium hydroxide (Phillips’™ Milk of Magnesia), 5-15 mL or 650 mg to 1.3 g tablets up to 4 times/d as needed; magnesium sulfate (Epsom salts ®), 10 to 15 g in a glass of water; and sodium phosphate (Fleet ®), 20-30 mL as a single dose.

Lubricant Cathartics/Emollients

These agents act to ease passage of stool by decreasing water absorption and lubricating the intestine. One agent is mineral oil (Kondremul ®). Dosage for adults and children >12 years of age is 15 to 45 mL once daily or divided dose. For children 6 to <12 years of age, dosage is 5 to 15 mL once daily or divided dose.

Note: All use of mineral oil, especially chronically, poses a significant nutritional problem, since mineral oil reduces absorption of the lipid-soluble vitamins (e.g., vitamins A, D, E, and K). Use in elderly patients, particularly those who exhibit high risk for aspiration, is not appropriate. Orally administered mineral oil can produce lipid pneumonia in these patients, a fatal complication. Prolonged, frequent, or excessive use may result in dependence or decrease absorption of fat-soluble vitamins.

Intestinal Stimulants/Irritants

These agents directly act on intestinal mucosa, stimulate myenteric plexus, and alter water and electrolyte secretion. Specific agents and usual dosages are bisacodyl (Dulcolax ®), 5 to 15 mg (usually 10 mg) as a single dose daily; senna, dose varies with formulation; and casanthranol (Dialose Plus ®, Peri-colace ®), dose varies with formulation.

Hyperosmotic

Local irritation and hyperosmotic action are produced by these agents. Examples and usual dosage include two types of agents. The first type is glycerin, adults and children <12 years of age, one suppository high in the rectum and retained 15 to 30 minutes; it need not melt to produce laxative action. A second type is lactulose (Cephulac ®, Chronulac ®), adults and children <12 years of age, 15 to 30 mL (10 to 20 g) daily, increased to 60 mL/d if necessary.

A third agent is the sugar alcohol, sorbitol 70%, 30-50 g/d. See bowel-cleansing (also called bowel preparation) agents for a discussion of GoLytely ® (polyethylene glycol-electrolyte solution). Combination products include docusate and casanthranol (Peri-Colace ®), one or two at bedtime with a full glass of water.

The patient presented a classic example of constipation resulting from narcotic analgesic administration, without any concomitant laxative program. An unnecessary hospital admission, a great deal of discomfort for the patient, and an unpleasant task for the nursing staff could all have been avoided.

As a physician working in palliative care, I have been continually confronted with patients’ problems of constipation. No other preventable symptom produces so much distress for the patient and the caring family. It is common for physicians either to omit completely any prescription for laxatives or to write a prescription for laxatives “as needed” or ‘laxative of choice” and to leave further management to nurses. The implication is that laxatives are administered only when constipation is present, as a treatment, rather than on a regular, individually adjusted, dosage schedule to prevent further problems.

Constipation is defined as a decrease in the frequency of bowel movements accompanied by a prolonged and difficult passage of feces, followed by an uncomfortable sensation of incomplete evacuation. Frequency of bowel movements can vary from three weekly to three daily, so what is constipation for one patient can be normal for another. Careful evaluation of constipation will require attention to frequency, consistency of stool, and ease of evacuation. Several symptoms can appear: low back pain, abdominal distress, distension, or flatulence.

Incidence

Obstinate constipation was described by Bockus as one of the most common conditions that the physician is called upon to treat, and one of the most often mismanaged.

Constipation is a common and distressing symptom in cancer patients. St. Christopher’s Hospice in London, England, reported that 45% of male patients and 43% of female patients on admission complained of constipation. At Sir Michael Sobell House, Oxford, 78% of patients on morphine received a laxative. The incidence of the problem’s occurring at some time during the course of the disease approaches 100%.

Causes in Cancer Patients

Contributing Factors

Certain contributing factors are particularly common in cancer patients and should be evaluated in any differential diagnosis.

1. Physiologic factors include advanced age, decreased exercise, especially in those who are bedridden, decreased bulk in diet, dehydration, inconvenience (inability to reach the toilet when the urge to defecate is present), depression, diminished awareness of loaded rectum, and poor dentition leading to inadequate nutrition.

2. Structural (anatomical-pathologic) factors include intracolonic (partial bowel obstruction, diverticulosis, tumour, bleeding, irritable or “cathartic colon,” ischemic colitis, and stricture), extracolonic (tumour or ascites), and anal (fissure, hemorrhoids, stricture, and proctitis from radiation).

3. Metabolic factors include hypercalcemia, hypokalemia, and uremia.

4. Neurologic factors include neuropathy (chemotherapy-induced or diabetic), compression of nerve roots or of spinal cord, and cauda equina.

5. Drugs affecting the bowel include opiates, antacids (calcium and aluminum compounds), anticholinergic drugs (belladonna alkaloids), antidepressive agents, phenothiazines, anticonvulsants, and diuretics.

Narcotics

Opiates increase the tone and non-propulsive motility of both ileum and colon. There is ample evidence that the opiates have both local effects on the gut and central nervous effects producing changes in motility of the bowel.

Treatment

Initially simple measures should be tried, such as increasing dietary fibre and increasing fluid intake. Patients should be encouraged to have a bowel movement when the urge occurs by providing a commode that is easily accessible. Almost always an additional systematic laxative regimen will be needed for cancer patients receiving narcotics.

All laxatives work by increasing motor activity, which promotes peristalsis, or by altering hydration of the stool. Physicians need to be acquainted with only a few agents in order to prescribe appropriately. Most effective is the use of a combination of a stool softener and a stimulant. A stimulant alone can lead to abdominal cramps. If a softener alone is given, the patient can develop a loaded rectum with soft stool.

Laxatives

Laxative drugs can be divided into five groups: bulk agents (regulators), lubricants and stool softeners, small bowel flushers (salts and non-absorb-able sugars, i.e., osmotic drugs,) stimulants, and anthracenes. Their site of action is indicated in Table 1.

Bulk Agents. Dietary fibre retains several times its weight in water. Foods containing wheat bran and fibre are particularly useful in chronic constipation, but the anorexia so common in advanced cancer limits dietary intake. Psyllium (Metamucil et al.) will increase the water content of the stool as well as the rate of colonic transit. A high fluid intake is required, a limiting factor in most patients with advanced disease. Dietary fibre and bulk agents are contra-indicated in intestinal obstruction, whether partial or complete.

Lubricants and Stool Softeners. Docusate sodium (Colace, Regulex, et al.) is a detergent that acts by drawing water and sodium into the bowel lumen. The dosage is regulated according to the consistency of stool, usually 100 to 600 mg/ day. (It is one of the most commonly used agents in Britain and in the United States.) Mineral oil, liquid paraffin, and other lubricants are contra-indicated. There is an ever-present risk of aspiration pneumonia, and when used for a longer term, of interference with absorption of fat-soluble vitamins. Mixtures of mineral oils with other cathartics is irrational.

Osmotic Agents. Saline cathartics usually contain magnesium or sodium ions, which retain fluid in the large bowel by osmotic pressure. These ions usually act in one or two hours. The major hazard of saline laxatives is their potential to cause electrolyte disturbances, especially in the elderly, who have a diminished capacity to return to an electrolyte balance. Partial absorption of sodium or magnesium can cause toxic effects in patients with cardiac or renal failure.

These agents are most effective if accompanied by a large oral intake of fluids. Commonly used saline cathartics include sodium sulphate, sodium phosphate, magnesium sulphate (Epsom Salt), magnesium hydroxide, and magnesium citrate. Lactulose (Chronulac, Lactulax, et al.) is a non-absorbable sugar that exerts similar osmotic effect. It is reported to be useful in patients with exacerbated abdominal discomfort. It is tolerated better than other drugs by some patients, but is also more costly.

Stimulants. Surface wetting agents and stimulant laxatives both work chiefly on contact with the intestinal mucosa. Contact laxatives change the absorption of water and electrolytes by the mucosa of the gut and soften the feces. The stimulant laxatives all enhance propulsive peristalsis. Because the effect is delayed for six to nine hours, they are best taken at bedtime. Examples include bisacodyl (Dulcolax et al.) by tablet or suppository.

Included in the anthracenes are cascara and senna, both containing glycosides. Senna, a contact laxative, is activated by bacterial action in the large bowel. It is usually prescribed in tablets or granules but is also available in liquid (X-Prep).

Rectal Measures

Suppositories. A combination of one glycerine suppository (which attracts water into the rectum) and a bisacodyl suppository (which stimulates the musculature) is often effective. Suppositories should be placed against the mucosal wall rather than pushed into the stool. Suppositories work quite quickly and should be given 30 minutes before breakfast or supper to take advantage of the gastrocolic reflex. Suppositories, when used regularly for several weeks, can cause a mild proctitis.

Enemas. A phosphate enema (Fleet) can help to evacuate the lower rectum. If stool is higher in the colon, a normal saline enema can be tried. If ineffective, an oil enema, delivered high up in the rectum and retained for about two or three hours, if possible, will soften stool; if expelled, it can be followed by a cleansing enema.

ManualDisimpaction. Impaction is the result of incomplete evacuation over time. The most common symptoms are rectal discomfort, rectal fullness, and tenesmus. There can be associated overflow incontinence of small amounts of liquid stool. The fecal impaction can be removed in patients who are not too sick by softening the mass from above using a stool softener. If this is not advisable, a gentle rectal examination is performed, using a single finger lubricated with 5% lidocaine ointment. After a few minutes, another finger can be inserted, which allows for dilatation of the anal sphincter without causing too much pain. The fingers are then used to “slice up” the impacted fecal mass. Several cleansing enemas are administered after removal of the pieces of stool. High fluid intake is mandatory on the day of disimpaction.

Rarely patients will require intravenous diazepam before the procedure to assist relaxation. In some centres a mixture of 50% nitrous oxide and 50% oxygen (Entonox) is used by inhalation for analgesia during the procedure.

Bowel Management

Proper assessment is the first step in the management of constipation. The patient should be asked about bowel habits and the use of laxatives.

Regular supervision of the laxative regimen by the physician and the nurse will be assisted by use of a recording form, where bowel movements, laxatives used, and other interventions can be noted daily. If the patient has not had a bowel movement for three days or more, the rectum should be examined for impaction. A plan should be developed by the physician in consultation with the attending nurse (Figure 1).

Conclusion

Constipation can be considered an iatrogenic complication. Indeed, constipation is one of the most frequent and distressing symptoms in cancer patients. Too frequently it becomes a major problem if the constipating potential of other drugs is not recognized. When anticipated, constipation can be easily managed by using a protocol, as suggested above. An appropriate recording form, especially when the patient is at home, will facilitate communication between the patient, nurse, and physician. It will assist in the successful prevention of constipation in

Risk Factors

The major risk factors for constipation in the elderly are the same as in younger people: low-fiber diet and low fluid intake. Other risk factors include lack of exercise, drug therapy, depression, and dementia (possibly because the patient ignores the urge to defecate), diabetes (probably because of autonomic neuropathy), stroke, metabolic imbalances (hypokalemia, hypercalcemia), and chronic laxative use. A number of medications are constipating, including anticholinergics (such as antipsychotics and tricyclic antidepressants), narcotics, diuretics, calcium channel blockers, iron supplements, aluminum antacids, Pepto Bismol, some anticonvulsants, nonsteroidal anti-inflammatory agents, and possibly angiotensin-converting enzyme inhibitors.

Fiber is the treatment of choice for constipation. Dietary fiber intake is generally deficient in the United States, and studies have shown that increasing bran intake reduces transit time, even in nursing home patients. Side effects from a high-fiber diet include bloating, flatulence, and irregular bowel movements, particularly in the first 2 to 3 weeks, which may reduce compliance. Phytic acid in crude bran may also decrease calcium absorption. Since low fluid intake plays an important role in constipation, people should drink at least 1500 mL of fluid a day, with increased intake in the summer. Patients on diuretics with stable cardiovascular status should also increase fluid intake. Regular exercise is also important; even maintaining erect posture can help limited-mobility patients in nursing homes.

Stimulant laxatives – phenolphthalein, castor oil, bisacodyl (Dulcolax / Ciba Geigy), and senna (Senakot / Purdue Frederick) — account for 25% of OTC laxative sales. They should be avoided when possible, as they can cause considerable side effects, particularly in the elderly. Acute reactions include cramping and vomiting, and long-term usage can lead to electrolyte disturbance, fat malabsorption, fat-soluble vitamin deficiency, and dependence. Senna (given at bedtime) is the best tolerated, although bisacodyl suppositories are fairly well tolerated and helpful for rectal dyschezia in the elderly. In one double-blind study of 77 nursing home patients with chronic constipation, a senna/fiber combination was effective, well tolerated, and less expensive than other options.

Bulk Laxatives

Bulk laxatives also account for 25% of Over-the-counter (OTC) laxative sales. Natural products (e.g., psyllium) and synthetic products (calcium polycarbophil and methylcellulose) absorb water and provide a bulkier stool that is easier to expel. Advantages include efficacy, long-term safety, and, in the case of psyllium, an ability to lower cholesterol. Disadvantages include flatulence (usually subsiding in 1 to 2 weeks), impaction when water intake is insufficient, unpalatability, and noncompliance. Magnesium salts – including magnesium hydroxide (Milk of Magnesia) and magnesium citrate – draw fluid into the bowel lumen, prompting evacuation within 3 hours. Side effects include cramping, watery stools, dehydration, and hypermagnesemia with chronic use.

Hyperosmolar laxatives – nonabsorbable disaccharides such as lactulose (Chronulac / Marion Merrell Dow), sorbitol, and glycerin (in suppository form) – osmotically increase intraluminal fluid. Lactulose is safe in the long term and has been used effectively even in frail elderly patients. Polyethylene glycol (Golytely / Braintree) is a potent hyperosmolar agent that is used for bowel cleansing before colonoscopy and to treat fecal impaction. Fecal softeners – such as docusate sodium (Colace / Apothecon) – increase secretion of water, sodium, and chloride into the gut. Docusate does not have laxative actions. It should not be used to treat chronic constipation, but should be reserved for patients who must avoid straining at the stool (e.g., angina patients). Enemas induce evacuation as a response to colonic distension, and also by plain lavage. Frequent use leads to electrolyte disturbance and damage to the rectal mucosa; incorrect use increases the risk of perforation of the rectum.

Harari et al. recommend that elderly patients with clinical constipation be treated with a daily bulk laxative plus adequate fluid. If this is poorly tolerated or ineffective, sorbitol may be added or substituted at 30 mL up to four times daily. When straining is a major complaint, or when rectal evacuation is a problem, suppositories can be administered after breakfast (glycerin suppositories daily or bisacodyl up to three times a week). Regular tap water enemas (up to three times a week) may be necessary to prevent fecal impaction. When impaction does occur, manual disimpaction followed by oil retention enemas with subsequent tap water enemas should be given daily until there are no signs of impaction. Sorbitol 30 mL/day can be administered along with senna 30 mg (up to three times a day) and daily tap water enemas until the constipation resolves.