What treatments are available for constipation?
There are many treatments for constipation,and the best approach relies on a clear understanding of the underlying cause.
Dietary fiber (bulk-forming laxatives)
The best way of adding fiber to the diet isincreasing the quantity of fruits and vegetables that are eaten. This means aminimum of five servings of fruits or vegetables every day. For many people,however, the amount of fruits and vegetables that are necessary may beinconveniently large or may not provide adequate relief from constipation. Inthis case, fiber supplements can be useful.四川省第四人民医院消化内科常玉英
Fiber is defined as material made by plantsthat is not digested by the human gastrointestinal tract. Fiber is one of themainstays in the treatment of constipation. Many types of fiber within theintestine bind to water and keep the water within the intestine. The fiber addsbulk (volume) to the stool and the water softens the stool.
There are different sources of fiber andthe type of fiber varies from source to source. Types of fiber can becategorized in several ways, for example, by their source.
The most common sources of fiber include:
fruits and vegetables,
wheat or oat bran,
psyllium seed (for example, Metamucil,Konsyl),
synthetic methyl cellulose (for example,Citrucel), and
polycarbophil (for example, Equilactin,Konsyl Fiber).
Polycarbophil often is combined withcalcium (for example, Fibercon). However, in some studies, thecalcium-containing polycarbophil was not as effective as the polycarbophilwithout calcium.
A lesser known source of fiber is anextract of malt (for example, Maltsupex); however, this extract may softenstools in ways other than increasing fiber.
Increased gas (flatulence) is a common sideeffect of high-fiber diets. The gas occurs because the bacteria normallypresent within the colon are capable of digesting fiber to a small extent. Thebacteria produce gas as a byproduct of their digestion of fiber. All fibers, nomatter what their source, can cause flatulence. However, since bacteria vary intheir ability to digest the various types of fiber, the different sources offiber may produce different amounts of gas. To complicate the situation, theability of bacteria to digest one type of fiber can vary from individual to individual.This variability makes the selection of the best type of fiber for each person(for example, a fiber that improves the quality of the stool without causingflatulence) more difficult. Thus, finding the proper fiber for an individualbecomes a matter of trial and error.
The different sources of fiber should betried one by one. The fiber should be started at a low dose and increased everyone to two weeks until either the desired effect on the stool is achieved ortroublesome flatulence interferes. (Fiber does not work overnight.) Ifflatulence occurs, the dose of fiber can be reduced for a few weeks and thehigher dose can then be tried again. (It generally is said that the amount ofgas that is produced by fiber decreases when the fiber is ingested for aprolonged period of time; however, this has never been studied.) If flatulenceremains a problem and prevents the dose of fiber from being raised to a levelthat affects the stool satisfactorily, it is time to move on to a differentsource of fiber.
When increasing amounts of fiber are used,it is recommended that greater amounts of water be consumed (for example, afull glass with each dose). In theory, the water prevents "hardening"of the fiber and blockage (obstruction) of the intestine. This seems like simpleand reasonable advice. However, ingesting larger amounts of water has neverbeen shown to have a beneficial effect on constipation, with or without theaddition of fiber. (There is already a lot of water in the intestine and extrawater that is digested is absorbed and excreted in the urine.) It is reasonableto drink enough fluids to prevent dehydration because with dehydration theremay be reduced intestinal water.
Because of concern about obstruction,persons with narrowings (strictures) or adhesions (scar tissue from previoussurgery) of their intestines should not use fiber unless it has been discussedwith their physician. Some fiber laxatives contain sugar, and patients withdiabetes may need to select sugar-free products.
Lubricant laxatives
Lubricant laxatives contain mineral oil aseither the plain oil or an emulsion (combination with water) of the oil. Theoil stays within the intestine, coats the particles of stool, and presumablyprevents the removal of water from the stool. This retention of water in thestool results in softer stool. Mineral oil generally is used only for theshort-term treatment of constipation since its long-term use has severalpotential disadvantages.
The oil can absorb fat-soluble vitaminsfrom the intestine and, if used for prolonged periods, may lead to deficienciesof these vitamins. This is of particular concern in pregnancy during which anadequate supply of vitamins is important for the fetus. In the very young orvery elderly in whom the swallowing mechanism is not strong or is impaired bystrokes, small amounts of the swallowed oil may enter the lungs and cause atype of pneumonia called lipid pneumonia. Mineral oil also may decrease theabsorption of some drugs such as warfarin (Coumadin) and oral contraceptives,thereby decreasing their effectiveness. Despite these potential disadvantages,mineral oil can be effective when short-term treatment is necessary.
Emollient laxatives (stool softeners)
Emollient laxatives are generally known asstool softeners. They contain a compound called docusate (for example, Colace).Docusate is a wetting agent that improves the ability of water within the colonto penetrate and mix with stool. This increased water within the stool softensthe stool. Although studies have not shown docusate to be consistentlyeffective in relieving constipation. Stool softeners often are used in thelong-term treatment of constipation. It may take a week or more for docusate tobe effective. The dose should be increased after one to two weeks if no effectis seen.
Although docusate generally is safe, it mayincrease the absorption of mineral oil and some medications from the intestine.Absorbed mineral oil collects in tissues of the body, for example, the lymphnodes and the liver, where it causes inflammation. It is not clear if thisinflammation has any important consequences, but it generally is felt thatprolonged absorption of mineral oil should not be allowed. The use of emollientlaxatives is not recommended together with mineral oil or with certainprescription medications. Emollient laxatives are commonly used when there is aneed to soften the stool temporarily and make defecation easier (for example,after surgery, childbirth, or heart attacks). They are also used forindividuals with hemorrhoids or anal fissures.
Hyperosmolar laxatives
Hyperosmolar laxatives are undigestible,unabsorbable compounds that remain within the colon and retain the water thatalready is in the colon. The result is softening of the stool. The most commonhyperosmolar laxatives are lactulose (for example, Kristalose), sorbitol, andpolyethylene glycol (for example, MiraLax). and are available by prescriptiononly. These laxatives are safe for long-term use and are associated with fewside effects.
Hyperosmolar laxatives may be digested bycolonic bacteria and turned into gas, which may result in unwanted abdominalbloating and flatulence. This effect is dose-related and less with polyethyleneglycol. Therefore, gas can be reduced by reducing the dose of the laxative. In somecases, the gas will decrease over time.
Saline laxatives
Saline laxatives contain non-absorbableions such as magnesium, sulfate, phosphate, and citrate [for example, magnesiumcitrate (Citroma), magnesium hydroxide, sodium phosphate). These ions remain inthe colon and cause water to be drawn into the colon. Again, the effect issoftening of the stool.
Magnesium also may have mild stimulatoryeffects on the colonic muscles. The magnesium in magnesium-containing laxativesis partially absorbed from the intestine and into the body. Magnesium iseliminated from the body by the kidneys. Therefore, individuals with impairedkidney function may develop toxic levels of magnesium from chronic (longduration) use of magnesium-containing laxatives.
Saline laxatives act within a few hours. Ingeneral, potent saline laxatives should not be used on a regular basis. Ifmajor diarrhea develops with the use of saline laxatives and the lost fluid isnot replaced by the consumption of liquids, dehydration may result. Forconstipation, the most frequently-used and mildest of the saline laxatives ismilk of magnesia. Epsom Salt is a more potent saline laxative that containsmagnesium sulfate.
Stimulant laxatives
Stimulant laxatives cause the muscles ofthe small intestine and colon to propel their contents more rapidly. They alsoincrease the amount of water in the stool, either by reducing the absorption ofthe water in the colon or by causing active secretion of water in the smallintestine.
The most commonly-used stimulant laxativescontain cascara (castor oil), senna (for example, Ex-Lax, Senokot), and aloe.Stimulant laxatives are very effective, but they can cause severe diarrhea withresulting dehydration and loss of electrolytes (especially potassium). Theyalso are more likely than other types of laxatives to cause intestinalcramping. There is concern that chronic use of stimulant laxatives may damagethe colon and worsen constipation, as previously discussed. Bisacodyl (forexample, Dulcolax, Correctol) is a stimulant laxative that affects the nervesof the colon which, in turn, stimulate the muscles of the colon to propel itscontents. Prunes also contain a mild colonic stimulant.
Tegaserod (Zelnorm)
Tegaserod (Zelnorm) was approved in 2002 bythe FDA specifically for the treatment of abdominal pain and constipation inwomen with irritable bowel syndrome. In March of 2007, the FDA asked Novartis,the company manufacturing tegaserod, to suspend sales of tegaserod in the U.S.because a retrospective analysis of data by Novartis from more than 18,000patients showed a slight difference in the incidence of cardiovascular events(heart attacks, strokes and angina) among patients taking tegaserod compared toplacebo. The data showed that cardiovascular events occurred in 13 out of11,614 patients treated with tegaserod (.11%), compared to one cardiovascularevent in 7,031 (.01%) placebo-treated patients. However, it is unclear whethertegaserod actually causes heart attacks and strokes. Doctors and scientistswill be scrutinizing the data to determine the long-term safety of tegaserod.
The mechanism whereby tegaserod relievesconstipation (and abdominal bloating and pain) is interesting and is related toits effects on the intestinal serotonin, a chemical that controls contractionsof intestinal muscles. The contractions of the intestinal muscles controltransit of digesting food through the intestine. More contractions speedtransit, fewer contractions slow transit. In constipated patients, contractionsare fewer.
Serotonin is a chemical manufactured bynerves in the intestine that is released and then binds to muscle cells.Depending on which receptor it binds to on the muscle, serotonin can eitherpromote or prevent contractions. The serotonin 5-HT4 receptor is a receptorthat prevents contractions when serotonin binds to it. Tegaserod blocks the5-HT4 receptor, prevents serotonin from binding to it, and thereby increasescontractions of the intestinal muscles. The increased contractions speed thetransit of digesting food and reduces constipation. In addition, tegaserodreduces the sensitivity of the intestinal pain-sensing nerves and can therebyreduce abdominal pain.
In large placebo controlled trialsinvolving men and women with chronic constipation, tegaserod was more effectivethan placebo in increasing the number of spontaneous bowel movements andreducing straining, abdominal bloating, abdominal pain, and abdominaldiscomfort. The most common side effect of tegaserod was diarrhea, which wasusually mild or moderate and generally resolved within a few days whilecontinuing treatment.
Lubiprostone (Amitiza)
Lubiprostone (Amitiza) is a selectivechloride channel activator that increases secretion of chloride ions from thecells of the intestinal lining into the intestinal lumen. Sodium ions and waterthen follow the chloride ions into the lumen, and the water softens the stool.The FDA approved lubiprostone for the treatment of chronic constipation in bothmen and women in February 2006. At a dose of 24 micrograms twice a day,lubiprostone significantly and promptly increased bowel movements, improvedstool consistency, and decreased straining. The most common side effect ofinitial clinical studies was mild to moderate nausea in 32% of patients treatedwith lubiprostone, compared to 3% of the controls. More long term studies ofefficacy and side effects are needed to determine the place of lubiprostone inthe treatment of constipation.
Enemas
There are many different types of enemas.By distending the rectum, all enemas (even the simplest type, the tap waterenema) stimulate the colon to contract and eliminate stool. Other types ofenemas have additional mechanisms of action. For example, saline enemas causewater to be drawn into the colon. Phosphate enemas (for example, Fleetphosphosoda) stimulate the muscles of the colon. Mineral oil enemas lubricateand soften hard stool. Emollient enemas (for example, Colace Microenema)contain agents that soften the stool.
Enemas are particularly useful when thereis impaction, which is hardening of stool in the rectum. In order to beeffective, the instructions that come with the enema must be followed. Thisrequires full application of the enema, appropriate positioning after the enemais instilled, and retention of the enema until cramps are felt. Defecationusually occurs between a few minutes and one hour after the enema is inserted.
Enemas are meant for occasional rather thanregular use. The frequent use of enemas can cause disturbances of the fluidsand electrolytes in the body. This is especially true of tap water enemas.Soapsuds enemas are not recommended because they can seriously damage therectum.
Suppositories
As is the case with enemas, different typesof suppositories have different mechanisms of action. There are stimulantsuppositories containing bisacodyl (for example, Dulcolax). Glycerinsuppositories are believed to have their effect by irritating the rectum. Theinsertion of the finger into the rectum when the suppository is placed mayitself stimulate a bowel movement.
Combination products
There are many products that combinedifferent laxatives. For example, there are oral products that combine sennaand psyllium (Perdiem), senna and docusate (Senokot-S), and senna and glycerin(Fletcher's Castoria). One product even combines three laxatives, senna-likecasanthranol, docusate, and glycerin (Sof-lax Overnight). These products may beconvenient and effective, but they also contain stimulant laxatives. Therefore,there is concern about permanent colonic damage with the use of these products,and they probably should not be used for long-term treatment unless non-stimulanttreatment fails.
Miscellaneous drugs
Several prescribed drugs that are used totreat medical diseases consistently cause (as a side effect) loose stools, evendiarrhea. There actually are several small studies that have examined thesedrugs for the treatment of constipation.
Colchicine
Colchicine is a drug that has been used fordecades to treat gout. Most patients who take colchicine note a loosening oftheir stools. Colchicine has also been demonstrated to relieve constipationeffectively in patients without gout.
Misoprostol (Cytotec)
Misoprostol (Cytotec) is a drug usedprimarily for preventing stomach ulcers caused by nonsteroidal antiinflammatorydrugs such as ibuprofen. Diarrhea is one of its consistent side-effects.Several studies have shown that misoprostol is effective in the short termtreatment of constipation. Misoprostol is expensive, and it is not clear if itwill remain effective and safe with long-term use. Therefore, its role in thetreatment of constipation remains to be determined.
Orlistat (Xenical)
Orlistat (Xenical) is a drug that is usedprimarily for reducing weight. It works by blocking the enzymes within theintestine that digest fat. The undigested fat is not absorbed, which accountsfor the weight loss. Undigested fat is digested by bacteria within theintestine and the products of this bacterial digestion promote the secretion ofwater. The products of digestion also may affect the intestine in other ways,for example, by stimulating the intestinal muscles. In fact, in studies,orlistat has been shown to be effective in treating constipation. Orlistat hasfew important side effects, which is consistent with the fact that only verysmall amounts of the drug are absorbed from the intestine.
It is unclear if these prescribed drugsshould be used for the treatment of constipation. Although it is difficult torecommend them specifically just for the treatment of constipation, they mightbe considered for constipated individuals who are overweight, have gout, orneed protection from nonsteroidal antiinflammatory drugs.
Exercise
People who lead sedentary lives are morefrequently constipated than people who are active. Nevertheless, limitedstudies of exercise on bowel habit have shown that exercise has minimal or noeffect on the frequency of bowel movements. Thus, exercise can be recommendedfor its many other health benefits, but not for its effect on constipation.
Biofeedback
Most of the muscles of the pelvissurrounding the anus and rectum are under some degree of voluntary control.Thus, biofeedback training can teach patients with pelvic floor dysfunction howto make their muscles work more normally and improve their ability to defecate.During ano-rectal biofeedback training, a pressure-sensing catheter is placedthrough the anus and into the rectum. Each time a patient contracts themuscles, the muscles generate a pressure that is sensed by the catheter andrecorded on a screen. By watching the pressures on the screen and attempting tomodify them, patients learn how to relax and contract the muscles morenormally.
Surgery
For individuals with problematicconstipation that is due to diseases of the colon or laxative abuse, surgery isthe ultimate treatment. During surgery, most of the colon, except for therectum (or the rectum and part of the sigmoid colon), is removed. The cut endof the small intestine is attached to the remaining rectum or sigmoid colon. Inpatients with colonic inertia, surgery is reserved for those who do not respondto all other therapies. If the surgery is to be done, there must be no diseaseof the small intestinal muscles. Normal small intestinal muscles are evidencedby normal motility studies of the small intestine itself.
Electrical pacing
Electrical pacing is still in itsexperimental phases. Electrical pacing may be done using electrodes implantedinto the muscular wall of the colon. The electrodes exit the colon and areattached to an electrical stimulator. Alternatively, stimulation of the sacralskin can be used to stimulate nerves going to the colon. These techniques arepromising, but much more work lies ahead before their role in treatingconstipation, if any, has been defined.