Of all the people who suffer from IBS, approximately one-third have problems with constipation. The term constipation means different things to different people. When some people say that they are constipated, they mean that they have infrequent bowel movements, maybe every 3 to 4 days. Other people use the term to refer to excessive straining in order to have a bowel movement or to pain or discomfort with the passage of stool. Still others mean that they do not feel as if they have completely emptied all the stool from their rectum (this is called “incomplete evacuation”). These different meanings are important to point out, because when you see your physician and tell him or her that you are constipated, your doctor may infer that you mean one of these definitions when in fact you mean another. Both patients and physicians need to be specific about these details for the most appropriate treatments to be chosen.
The first line of treatment for people who have mild symptoms of IBS and constipation generally focuses on lifestyle modifications, changes in diet, and the use of fiber supplements. During the initial patient evaluation in our clinic, we review the amount of fluid that the person takes in each day, determine the amount of dietary fiber consumed, and discuss whether the patient exercises regularly and the type of exercise. We also carefully review what treatments the patient has tried in the past, including over-the-counter products, prescription medications, natural medicines, homeopathic medicines, and any other alternative treatment.
There are very few scientific data to support the idea that drinking more water will lead to a significant improvement in constipation. The body has an amazing ability to absorb large amounts of fluid from both the small intestine and the colon (the small intestine can absorb up to 14 liters of water per day, and the colon can absorb up to 4 to 5 liters of water per day). Thus, it is difficult to drink so much fluid that the fluid intake alone will increase the frequency of stools or make them softer and looser.
Although for years we have been told that we should drink at least 8 glasses of water (64 ounces total) per day, it hasn’t been scientifically established that this specific amount is vital to good health. We all need to drink adequate amounts of fluid in order to remain hydrated and maintain a normal amount of fluid in our bloodstream. With a normal fluid balance, the kidneys, heart, skin, central nervous system, and muscles all function more efficiently and remain healthier. Your body will let you know when you have not had enough fluid, because you will feel a little more tired than usual, your mouth may feel dry, or your urine may be darker (more concentrated) than usual. Water is a healthy way to maintain normal hydration, because it avoids the extra sugar and calories incorporated in fruit juices and sports drinks and the gas found in carbonated drinks. Fluids should be available at each meal and throughout the day. Common sense dictates that if you are thirsty, you should drink. If you take certain medications, the accompanying instructions or your physician may tell you to take in more fluid than usual or to take each dose with a full glass of water. In particular, if you take fiber supplements (discussed below), you will need to take in enough fluid, because the fiber products work by becoming hydrated. If they are taken without sufficient fluid, they may actually worsen constipation. Overall, increasing fluid intake by itself leads to an improvement in constipation only in people who were truly dehydrated.
When physicians discuss constipation with patients, we generally focus on two aspects of diet: volume and fiber content. Although it is an often-neglected subject, the quantity of food you eat plays an important role in bowel health. Stool is largely material that cannot be broken down and absorbed by the GI tract (plus dead cells and lots of bacteria from the colon). People who go on a strict diet or severely limit their caloric intake quite often become constipated. An extreme example is anorexics, who typically suffer from constipation because they eat so little. If you need to lose weight, it is easy, with the right kind of diet, to take in plenty of volume and fiber without overdoing the calories. For a discussion of fiber, see the section just below.
Current dietary recommendations are that everybody should take in 25 to 30 grams of natural fiber each day. Natural fiber can be found in many different foodstuffs, including fresh fruits, fresh vegetables, and whole-grain breads and cereals (see Table 16.1). Fiber comes in two different forms—soluble and insoluble. Examples of foods that contain soluble fiber are potatoes and oatmeal, while commercial products that contain soluble fiber include Metamucil (psyllium), Citrucel (methylcellulose), and Benefiber (guar gum). Examples of foods that contain large amounts of insoluble fiber are bran flakes, kidney beans, and pears.
Soluble fiber can be broken down and digested by the GI tract, while insoluble fiber cannot. What are the advantages and disadvantages of using more of one kind of fiber than another? Because soluble fiber products can be broken down in the GI tract, they typically cause less gas and bloating. However, soluble fiber, because it is broken down and split by bacteria, does not absorb as much water as insoluble fiber. Thus soluble fiber may be less helpful in treating constipation than insoluble fiber.
Fiber generally has two major mechanisms of action. It increases stool volume, and it helps to speed up the transit of material through the GI tract. In addition, by providing bulk to the stool, fiber often increases the ease of evacuation and decreases straining. When it is difficult for people to take in adequate amounts of fiber through their diet, fiber supplements (methylcellulose, psyllium, polycarbophil, coarse bran, or ispaghula husk) can be used. Fiber supplements act as hydrophilic agents, meaning that they absorb water. By absorbing significant amounts of water, fiber adds bulk to the stool, preventing excessive dehydration of the stool as it passes through the colon and leading to more rapid transit of the stool through the intestinal tract.
Table 16.1. Fiber Content of Selected Foods
|
Serving size |
Total soluble and insoluble (in grams) |
Vegetables (cooked) |
|
|
Artichoke |
1 globe |
6.5 |
Asparagus |
½ cup |
1.8 |
Beans, green |
½ cup |
1.3 |
Beans, kidney |
½ cup |
5.7 |
Beans, lima |
½ cup |
6.1 |
Broccoli |
½ cup |
2.8 |
Cabbage, green |
½ cup |
2.1 |
Carrots |
½ cup |
2.6 |
Cauliflower |
½ cup |
2.0 |
Celery (raw) |
½ cup |
1.0 |
Corn |
½ cup |
2.0 |
Cucumber (raw) |
½ cup |
0.4 |
Eggplant |
½ cup |
1.2 |
Lettuce, iceberg (raw) |
½ cup |
0.4 |
Peas, green |
½ cup |
4.4 |
Potato, baked (with skin) |
½ cup |
1.5 |
Potato, sweet |
½ cup |
3.8 |
Spinach |
½ cup |
2.7 |
Squash, acorn |
½ cup |
4.0 |
Tomato (raw) |
½ cup |
1.0 |
Zucchini |
½ cup |
1.3 |
Fruits (uncooked) |
|
|
Apple (with peel) |
1 medium |
3.7 |
Apricots |
1 cup |
3.7 |
Banana |
1 medium |
2.7 |
Blackberries |
1 cup |
7.2 |
Blueberries |
1 cup |
3.9 |
Boysenberries |
1 cup |
7.2 |
Cantaloupe |
1 wedge |
1.3 |
Grapefruit |
1 medium |
2.8 |
Grapes |
1 cup |
1.6 |
Orange |
1 medium |
3.1 |
Pear (with peel) |
1 medium |
4.0 |
Pineapple |
1 cup |
1.9 |
Plums |
1 medium |
1.0 |
Prunes |
½ cup |
5.7 |
1 cup |
8.4 |
|
Strawberries |
1 cup |
3.4 |
Watermelon |
1 slice |
0.8 |
Grain Products and Nuts |
|
|
Bread |
|
|
Rye |
1 slice |
1.6 |
White |
1 slice |
0.6 |
Whole wheat |
1 slice |
2.0 |
Cereal |
|
|
Bran |
1 ounce |
9.7 |
Corn flakes |
1 ounce |
1.0 |
Oat bran (uncooked) |
1 ounce |
4.3 |
Oatmeal (uncooked) |
1 ounce |
3.0 |
Shredded wheat |
1 ounce |
2.8 |
Pasta |
2 ounces |
2.1 |
Popcorn |
1 cup (popped) |
1.0 |
Rice |
|
|
Brown (cooked) |
½ cup |
1.8 |
White (cooked) |
½ cup |
0.3 |
Almonds (roasted) |
½ cup |
6.4 |
Peanuts (roasted) |
½ cup |
6.1 |
In the past, treatment for IBS encouraged a low-fiber diet. The concern, before about 1970, was that additional fiber would “irritate” the GI tract and make symptoms of IBS worse. During the last 30 years, however, fiber has become a mainstay of therapy in the treatment of IBS. Especially in this era of “managed care,” in which insurance companies and health care plans try to carefully control the use of prescription medications, fiber products represent a safe, inexpensive dietary supplement that provides relief of constipation for some people. Despite its widespread use, however, the data do not agree about the effectiveness of fiber treatment in people who have IBS and constipation. Let’s begin by reviewing some of the research studies that have evaluated the potential benefits of fiber therapy.
One study, published in 1977, found that 14 patients who had IBS and were treated with a high-wheat-fiber diet noted an improvement in abdominal pain and bowel complaints, compared to 12 patients who had IBS and were placed on a low-wheat-fiber diet. Another study, published in 1980, followed a small group of patients who had IBS as they progressed from a “normal” diet (low in fiber) to a fiber-added diet (moderate in fiber) and then to a high-fiber diet. All patients noted an improvement in the transit of materials through the colon as fiber was added to the diet. Other small studies have also shown that fiber products (ispaghula husk, calcium polycarbophil [Equalactin], psyllium [Metamucil], methyl-cellulose [Citrucel]) have improved symptoms of constipation in patients who have IBS. In addition, when the results of many studies that had investigated the effects of fiber in people who have IBS and constipation were analyzed as a group (a type of research called meta-analysis), there was a consistent improvement in colonic transit time and an increase in stool output for patients treated with fiber.
These results seem encouraging, and in fact, many patients who have IBS do note an improvement in their constipation symptoms when treated with fiber supplements. However, improvement in transit time through the GI tract and an increase in stool weight do not always translate into an improvement in the other clinical symptoms of IBS. In fact, most of these studies did not show any improvement in the chronic abdominal pain and discomfort that characterize IBS. In addition, at least 30 percent of patients noted a significant worsening of bloating and abdominal distention with these agents (especially with insoluble fiber products). One study found that as many as 55 percent of patients who had IBS and were treated with bran fiber experienced significant aggravation of abdominal pain and distention.
In summary, adding fiber to the diet is a reasonable treatment for people who have constipation and may improve symptoms of constipation in some individuals who have IBS. If you decide to start a fiber supplement, begin slowly. If you start at the maximum dose on the first day, you are virtually guaranteed to feel worse, not better, due to problems with gas, bloating, and abdominal discomfort. I generally ask patients to begin with a small amount of fiber each day (a half teaspoon of psyllium, or half of a fiber tablet), taken before the evening meal with a large glass of water. Every five to seven days the patient slowly increases the dose, so that by the end of the month, the person is on the maximum recommended dose. This gives the GI tract time to adjust to the added volume of fiber, minimizes side effects, and allows the patient time to make other changes in daily routine that might be needed because of changes in bowel behavior.
If a person who has IBS is already on a high-fiber diet, adding more fiber will not improve symptoms of constipation, although the additional fiber will undoubtedly worsen complaints of bloating, gas, and distention. Research studies have consistently shown that fiber products do not improve abdominal pain and, in fact, may actually worsen it, because they can cause more bloating and distention.
Physicians often recommend exercise to their patients as a matter of course during a routine check-up or office visit. Certainly, exercise has been shown to improve many health conditions, including high blood pressure, diabetes, osteopenia (mild bone loss) and osteoporosis, obesity, and a variety of heart conditions. In addition, routine exercise can reduce stress, tension, and anxiety, improve mental health, and possibly lead to an improvement in the immune system. Limited data support the view that regular exercise improves motility in the GI tract. Patients who routinely exercise (jogging, walking, playing tennis, biking) often find that when they get out of their regular exercise pattern, they become constipated. This may reflect a direct effect of exercise on the GI tract, or the increase in constipation may be due to the change in daily routine or an accompanying change in diet. Because many patients find that some exercise seems to alleviate constipation, we often recommend that exercise be incorporated into a person’s weekly routine. Many people find that a brisk walk after breakfast or after dinner seems to stimulate the colon and ease evacuation of stool, especially when coupled with routine, scheduled bathroom time (see “Bowel Training” below). No large scientific study has evaluated the effects of exercise on IBS and constipation, however.
Having a bowel movement is normally an easy task routinely accomplished. As mentioned previously, there is a wide range of what can be considered normal bowel habits. Many people simply fall out of their natural habits, for a variety of reasons, and so become constipated. One of the most common reasons is ignoring the urge to have a bowel movement. In many people this urge occurs when awakening, and in others it typically occurs after eating. People who ignore this urge (sometimes described as a “crampy” sensation or a sensation of “pressure” or “fullness” in the rectum) can quickly become constipated. For example, office workers, teachers, truck drivers, or operating room nurses may get up, have breakfast and their morning cup of coffee or tea, and then go to work. They may then develop the urge to have a bowel movement, but the phone begins ringing, the fax machine has to be attended to, classes begin, the truck is on the highway, or the surgical case takes longer than expected. The urge to have a bowel movement is then ignored or actively suppressed. This urge may then disappear until the next day, when the same activities again prevent going to the bathroom to evacuate stool. All of a sudden, people who used to routinely have a bowel movement each morning are now doing so once each weekend.
Normally, the GI tract is very quiet at night but “wakes up” each morning with a wave of peristaltic activity at approximately four or five o’clock in the morning. This is one reason why some people have a bowel movement first thing in the morning. Eating food or drinking warm liquids stimulates the stomach and sets up a reflex with the colon, called the gastrocolic (or gastrocolonic) reflex. In many people, 15 to 45 minutes after food stimulates their stomach, they will feel the urge to have a bowel movement. (This is the same reflex that is so highly exaggerated in patients who have IBS and diarrhea that they can barely finish a meal before they are running to the bathroom.) This is an important reflex that should be taken advantage of by patients with constipation.
When we talk about bowel training, we basically mean listening to the normal signals that the body sends us every day and trying to accommodate them. The gut loves routines. This means getting up at approximately the same time each day, having breakfast (to help initiate the gastrocolic reflex), possibly drinking a large mug of caffeinated coffee or tea or taking a walk (to further stimulate the GI tract), and then setting aside time to use the bathroom at a scheduled time each day, typically 30 to 45 minutes after the morning meal. Ideally, this should be the same time each day. This simple routine, easy to incorporate in most people’s daily schedule, is a safe and very effective approach to improving constipation. Finally, some people find that it is easier to have a bowel movement if they place their feet on a small stool; this technique changes the shape of the pelvic floor (it helps widen the anorectal angle—see Chapter 6) and makes it easier to evacuate.
When patients first see a physician for treatment of IBS symptoms, they often have tried various medicines without adequate relief. As part of history taking, we review not only which medications have been tried and the dose of each (in milligrams, number of pills per dose, number of times per day), but also how the medication was taken (liquid, tablet, capsule; by mouth, suppository, injection), and for how long it was tried. Table 16.2 lists many of the medications, both prescription and nonpre-scription, that are used to treat constipation.
As we introduce new medications in a treatment program, I generally recommend that each be tried for a minimum of four weeks, so that the results can be properly evaluated (unless a side effect or adverse drug reaction occurs, requiring earlier cessation of use). Since many patients who have IBS have symptoms that have lasted for months or years, it is unfair to judge the value of any single medication after a trial of only a few days or a week.
We are all aware that medications are a two-edged sword. They can certainly improve the symptoms of medical conditions, whether the symptoms are acute or chronic in nature. However, all medicinal preparations have the potential for causing side effects—responses that are not the intended effect, are usually unwanted, and can be either benign or harmful. These potential side effects do not come only with prescription medications; they may be caused by over-the-counter products, dietary supplements (recall the controversy with ephedra in weight loss supplements), and complementary and alternative medications, including herbal preparations. Some medications can cause constipation or make it worse. Table 16.3 lists several of these substances. If you are taking one of these medications, at your next visit with your physician you may want to discuss whether the medicine is really needed or whether there is an alternative medication that would not be constipating.
Table 16.2. Medications Used to Treat Constipation
Chloride channel activators Lubiprostone (Amitiza) Combination agents Docusate sodium and sennoside (Senokot-S) Docusate sodium and casanthrol (Peri-Colace) Fiber Methylcellulose (Citrucel) Psyllium (Metamucil) Calcium polycarbophil (Equalactin, FiberCon) Guar gum, partially hydrolyzed (Benefiber) Coarse bran or ispaghula husk Guanylate cyclase C activators Linaclotide (Linzess) Herbal agents Aloe vera (Aloe barbadensis) Buckthorn (Rhamnus catharticus) Cascara sagrada (Rhamnus purshianus) Chinese rhubarb (Rheum palmatum) Frangula (Rhamnus frangula) Manna (Fraxinus ornus) Senna (Cassia senna) Miscellaneous Mineral oil Colchicine Misoprostol (Cytotec) Osmotic agents and unabsorbed sugars Magnesium hydroxide (Phillips Milk of Magnesia, Freelax) Magnesium citrate Polyethylene glycol (Miralax) Lactulose (Chronulac, Kristalose) Lactitol Sorbitol Stimulant laxatives Bisacodyl (Dulcolax, Gentlax) Senna, sennosides (Senokot, Ex-Lax, Swiss-Kriss) Aloe Cascara Stool softeners Docusate sodium (Colace) |
Stool softeners. Stool softeners are considered emollients because they act to soften and lubricate the stool, to a small degree. Docusate sodium (one brand name is Colace) is the best known of this type of medication. In usual doses, docusate (one pill twice a day) may increase the fluid content of stool by 3 to 5 percent, thereby softening the stool and allowing easier evacuation. No research study has demonstrated that stool softeners are any better than a placebo at treating symptoms of constipation. So, although stool softeners are safe and relatively inexpensive, they are rarely helpful for people who have constipation.
Osmotic agents. Osmotic agents act by drawing water into the intestinal tract. The increased fluid load in the GI tract helps to accelerate the movement of materials through the GI tract and helps to soften stool. Osmotic agents function differently from the stool softeners described above. Many agents in this class are sold over the counter. They are sometimes described as “salts” because they typically contain large amounts of magnesium or sulfate. Use of these agents for longer than two weeks can lead to elevated levels of magnesium in the bloodstream, which can be dangerous, especially in people with kidney problems such as renal insufficiency or renal failure. Typical osmotic agents are magnesium hydroxide (milk of magnesia), magnesium sulfate, or magnesium citrate. These medications are best used only intermittently to treat mild cases of constipation. They generally do not cause abdominal bloating or distention but may cause abdominal cramps and spasms.
Table 16.3. Medications That May Cause Constipation
Anticholinergic agents (hyoscyamine, dicyclomine, Detrol) Anticonvulsants (phenytoin, phenobarbital) Antidiarrheal agents (Imodium, Lomotil) Antihistamines (either alone or in cold remedies) Anti-Parkinsonian agents (L-Dopa) Antipsychotics (thorazine) Calcium channel blockers (diltiazem) Cholestyramine (Questran) Diuretics (lasix) Fiber, if not taken with adequate fluids Narcotics (oxycodone, Percocet, Vicodin) Nonsteroidal anti-inflammatory agents (ibuprofen, Motrin, Aleve) Sucralfate (Carafate) Tricyclic antidepressants (Elavil, Norpramin) |
Sugars that cannot be absorbed within the GI tract may also act as osmotic agents. These large sugar molecules draw water into the GI tract, thus stimulating gut transit. A good example is sorbitol, commonly used to sweeten gums, candies, and mints. Products containing sorbitol are often labeled “dietetic” or “sugar free,” since, not being absorbed, sorbitol does not contribute to caloric intake.
Polyethylene glycol (PEG) is another type of osmotic agent, but its chemical structure is quite different from the over-the-counter osmotic agents described above. PEG is a large, inert molecule that is not absorbed in the GI tract. PEG preparations are commonly used to help prepare patients for colonoscopy or flexible sigmoidoscopy. These agents are now sold in prescription form as well as over the counter with a variety of trade names (Miralax, Nu-Lytely) and generically as glycolax. In smaller doses, PEG can be used daily or intermittently to treat constipation. At present, the FDA has not approved PEG for long-term use. Although several small studies of its efficacy have shown that patients often note an improvement in symptoms of constipation, PEG preparations do not improve abdominal pain or bloating associated with IBS.
Stimulant laxatives. Products in this group (for instance, Dulcolax) contain senna, cascara, aloe, or bisacodyl. Many of these ingredients are derived from plants. All stimulant laxatives have two major mechanisms of action. They increase colonic contractions and they stimulate the intestinal tract to secrete water, which hastens the movement of materials through the GI tract. Small research studies have shown that senna both increases stool frequency and improves stool consistency in people who have constipation. At present, there are no randomized, controlled studies evaluating any of these agents in people who have IBS and constipation. In general, these medications are recommended for intermittent use only. However, contrary to popular opinion, long-term use of stimulant laxatives does not cause people to become dependent on them.
Long-term utilization of these medications may lead to discoloration of the colon, a condition called melanosis coli. This discoloration of the lining of the colon (ranging from black to dark yellow) occurs because these laxatives appear to cause premature death of some of the cells that line the colon. These dead cells are then ingested by other cells (macrophages), which break down dead cells. The break-down products are deeply pigmented, leading to the discoloration of the colonic mucosa. This condition is not dangerous and will slowly resolve once the person stops taking the laxative.
Side effects are fairly common with all of these agents and include cramps, abdominal pain, and diarrhea. Stimulant agents are found in widely-used products sold at supermarkets, health food stores, and nutrition centers. Note that laxatives containing phenolphthalein are no longer sold, because of concerns about their safety after reports of allergic reactions came to light.
Enemas and suppositories. Some people with constipation occasionally use either enemas or suppositories to treat their problem. Enemas work by softening stool and by stimulating the colon to contract. When an enema is used, the liquid can travel as high up as the descending colon (see Figure 6.1 for a diagram of the intestinal tract). The descending and sigmoid colon are where stool is normally stored until it is an appropriate time to have a bowel movement. The enema solution softens the stool that is stored there, which may improve the ease of evacuation. In addition, insertion of the tip of the enema bottle or tube into the rectum stimulates sensory receptors in the rectum and initiates reflexive contractions of both the sigmoid colon and rectum, further assisting the evacuation of stool.
Although a variety of enemas are sold over the counter, there are no studies comparing the effectiveness of one versus the other. Warm water enemas (using a hot water bottle and the correct tubing and tip) are obviously the cheapest and are usually just as effective as commercial products. In the case of warm water enemas, the water should be only warm, not hot, and should be slowly instilled, not forced into the rectum at high pressure by vigorously squeezing the bag. The tip of the enema bottle or tube should be lubricated with K-Y Jelly and inserted gently into the rectum. Forcing the tip or inserting it too deep can lead to serious injury. Although rare, there are cases where people have perforated (poked a hole in) their rectum by forcing the tip of the enema bottle in too forcefully or too deep. Enemas typically work best if the liquid can remain in place for 30 to 45 minutes, preferably while the patient is lying on his or her left side. The liquid should then be evacuated and is expected to carry the softened stool with it.
Some commercial enemas contain a large amount of phosphate. People who have kidney problems should avoid these agents, because the phosphate can be absorbed from the colon, leading to dangerously high levels in the blood. Lastly, some enemas can cause the mucosal lining to become significantly irritated and inflamed or even bleed. If this occurs, the enema should be immediately stopped and no further ones attempted until the reaction has been evaluated and has healed. This will require a visit to your health care provider, but the examination will probably be quick. Enemas can help some patients but are appropriate only for short-term, intermittent use.
Suppositories (glycerin is the type most commonly used) work in a similar manner to enemas. Inserting the suppository stimulates sensory receptors in the rectum, which then causes the rectum to contract. The glycerin may lubricate the rectum and add a small amount of moisture. Bisacodyl (Dulcolax) suppositories stimulate muscular contractions in the colon using a direct irritative effect that may lead to more forceful contractions of the colon but also to more pain, cramping, and spasms.
Neither of these types of treatment for constipation has been evaluated in large-scale trials. Overall, they are considered safe if used appropriately, but they do not affect the underlying causes of chronic constipation.
Other agents. One old-fashioned remedy for constipation is taking mineral oil or castor oil. In theory, the oil will soften the stool and lead to easier evacuation. However, taking these oils rarely helps constipation, and the oils pass through the GI tract without being absorbed and may seep out of the rectum, staining the clothes. Although an uncommon side effect, inflammation in the liver (hepatitis) may result from taking mineral oil, and chronic use has the potential to deplete the body of critical fat-soluble vitamins (vitamins A, D, K, and E). In addition, mineral oil should never be used by older people, because if it is inadvertently inhaled (aspirated), it can cause a life-threatening pneumonia.
Osmotic agents. Polyethylene glycol (PEG) is described above. It is now most commonly used in the over-the-counter form, although some insurance companies still pay for this medication if it is required for long-term use and is prescribed by a physician.
Unabsorbed sugars. Another class of prescription medication often used to treat patients who have IBS and constipation is unabsorbed sugars. These agents, which are sold under a variety of trade names, include lactulose, lactitol, mannitol, and sorbitol. We’ll look at lactulose as an example. Lactulose is made up of two sugar molecules (galactose and fructose) joined together. It is taken in the form of a sugary-sweet syrup that cannot be broken down and digested by the small intestine and instead passes into the colon, where it is broken down by the bacteria there. Because the sugar is not absorbed, it acts like an osmotic laxative, similar to milk of magnesia (see above), causing increased stool frequency and a softening of stool consistency. Because the sugars are not absorbed, they generally do not cause elevated blood sugar levels. Several small studies have shown that lactulose improves symptoms of constipation, but it has not been tested specifically in patients who have IBS and constipation.
A major side effect of the unabsorbed sugars is that they all have the potential to cause or worsen symptoms of gassiness, bloating, and distention, because they ferment in the colon, producing hydrogen gas and carbon dioxide. Although these products may improve constipation (increased frequency and softer stools), many patients find that the side effects far outweigh the benefits of these drugs. In my experience, these agents are not usually helpful for patients who have severe constipation.
Note that sorbitol is a common additive used by the food industry as a sweetener in sugar-free products. People who consume large amounts of sugar-free candies, gums, or mints that contain sorbitol often notice an increase in bloating, distention, and occasionally diarrhea.
Lubiprostone. Lubiprostone was approved by the FDA in 2008 for the treatment of IBS with constipation in women. It is sold under the brand name Amitiza. The recommended dose of lubiprostone is 8 micrograms (mcg) twice daily, although some patients who have IBS with constipation (IBS-C) just need 8 mcg once daily.
Lubiprostone is categorized as a chloride channel activator and works differently from all of the products described above. After being swallowed, lubiprostone stimulates the cells lining the small intestine and colon to secrete (release) small amounts of chloride followed by small amounts of sodium. The secretion of chloride and sodium (in effect, small amounts of salt) in turn causes water to enter the GI tract. The addition of water to the GI tract can help loosen stool and make it easier to pass. This active secretion of chloride followed by small amounts of water may stimulate the muscles and nerves of the GI tract, which can improve peristalsis.
Several large research studies have proven the effectiveness of lubiprostone in treating symptoms of IBS-C. One of the largest studies involved nearly twelve hundred men and women who had IBS-C. Patients in this study received either lubiprostone or a placebo for a 12-week period. Before and during the study, researchers measured the patients’ symptoms of IBS (abdominal pain, bloating, and constipation) so that the effectiveness and safety of lubiprostone could be determined. To be categorized as having responded to the treatment with lubiprostone, patients had to have most or all of their IBS-C symptoms improve for the majority of the 12-week study period. None of the medications described earlier in this chapter (over-the-counter or prescription) have been subjected to such a long study period or to such strict criteria. The results of this study showed that patients treated with lubiprostone were nearly twice as likely to have their IBS symptoms improve or resolve as compared to those patients who were given a placebo. Lubiprostone was also found to be very safe, without any significant side effects (other than mild nausea in some patients and diarrhea in others).
More recently, a similar study evaluated the long-term safety and efficacy of lubiprostone during a 48-week trial period. Lubiprostone remained both effective and safe during this prolonged period of use, which is important for patients who have IBS and typically have persistent symptoms that last months or years, thus requiring chronic medical therapy.
So why is lubiprostone currently approved only for women who have IBS and constipation, and not men? Although men were included in the research studies, there were far more women in the studies. The FDA did not have enough information to confidently state that men who have IBS and constipation would respond favorably to this medication. However, the FDA did approve lubiprostone for the treatment of chronic constipation in both men and women. This approval should be reassuring to men who have IBS and constipation, because symptoms of chronic constipation and IBS with constipation are similar, and because the underlying pathophysiology is often the same.
With regard to safety, lubiprostone has been proven safe to use in patients 65 years old and older who have symptoms of constipation. It has not yet been approved by the FDA in the pediatric population (younger than 18 years old), although studies to evaluate the safety and effectiveness of this medication for children and adolescents are ongoing. Even though less than 1 percent of lubiprostone is absorbed by a patient’s GI tract (this is one of the reasons it is so safe), it is always appropriate to be extra cautious with women who might become pregnant or who are breast-feeding. Thus, the FDA has recommended that this medication not be used for women who are breast-feeding or pregnant. But this recommendation does not apply just to lubiprostone—the vast majority of medications on the market should not be used by women who are pregnant or breast-feeding.
Linaclotide. Linaclotide is a new medication that was recently approved (August 30, 2012) by the FDA for the treatment of symptoms of IBS and constipation. It is sold under the trade name Linzess. Linaclotide, a small chemical that consists of only 14 amino acids, acts differently from all other available over-the-counter agents and prescription medications because it mimics the action of a natural chemical in the body. When ingested, linaclotide stimulates the production of a chemical called cGMP. When the level of this chemical is increased in the cells that line the GI tract, a series of reactions occur that ultimately result in an increased flow of electrolytes (bicarbonate and chloride) and water into the GI tract. Similar to lubiprostone, this increased flow accelerates movement of materials through the GI tract, which can improve symptoms of constipation.
The efficacy and safety of linaclotide has been proven in studies that included adult men and women with typical symptoms of IBS-C (lower abdominal pain and discomfort, bloating, and constipation). During the 12-week studies, patients were randomly placed into groups to receive either the study drug (linaclotide) or a placebo. Symptoms were measured at the beginning, middle, and end of the study to assess the effectiveness of linaclotide at improving symptoms of IBS and constipation. The studies clearly show that linaclotide improves symptoms of IBS-C, including symptoms of hard stool, straining, incomplete evacuation, and lower abdominal pain and bloating. Patients in the study tolerated linaclotide well; no serious side effects were identified. Some patients had symptoms of diarrhea (as with lubiprostone), although this may be more a sign of efficacy than a side effect of the medication. Linaclotide appears to be safe for long-term use. In a study of more than 800 patients for 26 weeks, linaclotide was effective at improving symptoms of IBS-C and was not found to have any serious side effects. Data on the use of linaclotide in elderly or pediatric populations are not yet available.
Medicine is constantly evolving, and researchers and clinicians are always searching for new medications and therapies to improve patients’ symptoms. Below is a brief list of medications that may become available in the future to help treat symptoms of IBS with constipation.
This medication helps stimulate serotonin receptors in the GI tract. It is approved for use in the European Union for the treatment of chronic constipation and has been shown to be safe and effective in both women and men. Its success at treating symptoms of chronic constipation means it probably also could improve symptoms in people who have IBS and constipation.
This medication also stimulates serotonin receptors in the GI tract. Preliminary studies have shown that it improves symptoms of constipation in both men and women. Additional studies are required to determine its efficacy and safety in people who have IBS.
This is a novel medication that is currently being developed. It acts differently from all the other agents described in this chapter by preventing the absorption of bile in the lower small intestine (ileum). If bile is not absorbed in the small intestine, more bile enters the colon, which acts to accelerate movement of materials through the colon. Preliminary studies have shown benefits for patients who have constipation. Additional trials are needed with patients who have IBS and constipation to determine its efficacy and safety.
• Contrary to popular opinion, simply drinking more water will rarely improve symptoms of constipation.
• Adding more natural or supplemental fiber to your diet will help with constipation if you are fiber deficient and if you take in enough fluid to hydrate the fiber supplement.
• Fiber does not treat the abdominal pain that characterizes IBS, and fiber can worsen symptoms of bloating.
• Osmotic agents (for example, milk of magnesia) and stimulant laxatives may temporarily improve constipation, but they usually are not effective for long-term use. In addition, these agents may worsen abdominal cramps, spasms, and pain, and they do not treat bloating.
• Lubiprostone (Amitiza) has been approved by the FDA for the treatment of IBS with constipation in women and for chronic constipation in both women and men.
• Linaclotide (Linzess), recently approved by the FDA, appears to be safe and effective at treating IBS-C symptoms.
• Other agents are currently under development for the treatment of IBS with constipation.