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Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) affects more than one in ten people. Little is known about the causes of IBS. It can be worsened by stress or emotional upsets. There may be differences in the symptoms of IBS between patients. This means that, of the many different treatment approaches available, you and your healthcare provider will need to select those that are most likely to help your individual symptoms.

What nondrug measures can I use?

Many people say that changing their diet is helpful. Some common culprits thought to make IBS worse are caffeine; alcohol; sorbitol (the artificial sweetener); fried or fatty foods; and gas-forming foods like cabbage, broccoli, or beans. Make sure that, if you do exclude something from your diet, you aren’t risking any type of deficiency (calcium, for example, from eliminating dairy products).
Adding fiber might be helpful for reducing the symptoms of IBS. Soluble fiber is best (supplements like Metamucil and dietary sources like applesauce, oatmeal, potatoes, and rice). Insoluble fiber, like wheat bran, doesn’t seem to work. The downside of fiber is that it can increase your chances of having gas and bloating. Add fiber gradually to reduce these effects.
You may also benefit from eating smaller, more frequent meals. Large meals can sometimes worsen IBS symptoms.
While stress does not appear to cause IBS, it may make the symptoms worse. Some patients have found that techniques to reduce stress or a good exercise program are helpful. There’s no harm in trying, so do what works best for you.

Are there medications I can take?

Over the years a number of different medications have been tried for IBS. You should always consult with your healthcare provider before trying any medication, especially nonprescription ones. Listed below are the most commonly used medications for IBS. Some of these medications require a prescription.
Antidiarrheal agents. Loperamide (Imodium) can be used for diarrhea, but it doesn’t help with stomach pain and bloating.
Antispasmodics. Hyoscyamine (Levsin [U.S.]), dicyclomine (Bentyl [U.S.], Bentylol [Canada]), and hyoscine butylbromide (Buscopan [Canada]) can reduce pain and cramping by decreasing muscle spasms in your intestinal tract. They’re especially helpful if your IBS symptoms are worsened by meals. However, antispasmodics may have some unpleasant side effects such as dry mouth, sedation, and constipation.
Laxatives. Osmotic laxatives, like polyethylene glycol or PEG (Miralax [U.S.], Lax-A-Day [Canada]) and milk of magnesia (MOM), can be tried for constipation.
Antidepressants. Antidepressants can reduce IBS symptoms as well as relieve depression and anxiety.
Herbal products. Several products have been tried that are available without a prescription. For example, peppermint oil is an antispasmodic that may help. You should consult with your healthcare provider before trying any alternative medications as these are active compounds and may have other physical effects and drug interactions that need to be considered.
Probiotics. Some probiotics might help with the symptoms of IBS, like bloating and gas. Look for products that contain Bifidobacteria, as this probiotic seems to be the most beneficial. Some products that contain Bifidobacteria include Align (U.S.), Activia (U.S.), Bifidox (Canada), or VSL #3.
Other therapies. Lubiprostone (Amitiza [U.S.]) is a prescription drug that’s helpful for women with IBS who have constipation. Alosetron (Lotronex [U.S.]) is another prescription drug that’s sometimes used in women with severe IBS with diarrhea. These drugs are expensive and have some important side effects, so they are generally used when other treatments have failed.

Where can I go for information?

There are some very good places on the internet where patients with IBS can go to keep up with current information about this disorder. A listing of these sites is given for your reference. Remember to talk with your healthcare provider about any information you find so you can discuss which treatments are best for you.
International Foundation for Functional GI Disorders: www.iamibs.org
The UNC Center for Functional GI and Motility Disorders: www.med.unc.edu/medicine/fgidc
The IBS Page: www.panix.com/~ibs/
IBS Resource Center: www.healingwell.com/ibs/
Canadian Society of Intestinal Research: www.badgut.com/
May 2009

Treatments for Irritable Bowel Syndrome (IBS)  
Irritable bowel syndrome (IBS) affects about 7% of individuals in North America. It’s defined by abdominal pain and altered bowel habits for a period of at least three months. Patients can experience predominant constipation (IBS-C), predominant diarrhea (IBS-D), or mixed symptoms (IBS-M). Unlike organic bowel diseases (e.g., celiac sprue, colitis, inflammatory bowel disease, etc), there are no structural or biochemical abnormalities associated with IBS.1 A new systematic review of therapies for IBS was recently published. This document discusses the treatments for IBS and their evidence for effectiveness. Recommendations for managing IBS patients are also included.

Fiber and Laxatives

Increasing fiber is one of the most common recommendations made to IBS patients, with the intent of reducing pain and regulating bowel function. However, studies show that insoluble dietary fiber, like wheat bran, is unlikely to improve symptoms.1
Patients may get improvement in overall IBS symptoms with psyllium hydrophilic mucilloid (Metamucil, etc). This is a soluble fiber, which absorbs water and forms a gel that helps food move smoothly through the GI tract. One study also showed some benefit of using calcium polycarbophil (FiberCon [U.S.], Prodiem Bulk Fibre Therapy [Canada], etc) compared to placebo. Like psyllium, calcium polycarbophil is a hydrophilic bulk-forming laxative.1
The downside of adding fiber is the potential for an increase in bloating, abdominal distension, and flatulence. Gradually adding fiber might help avoid this.1
One small study suggests that the osmotic laxative polyethylene glycol (PEG) (Miralax [U.S.], Lax-A-Day [Canada]) can double the frequency of bowel movements in patients with IBS-C. However, pain intensity is not reduced by osmotic laxatives.


Pooled data from studies of both tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) (n=789) show that these drugs are likely to improve overall symptoms of IBS, regardless of IBS type. About one in four patients treated will have some benefit.
The largest individual trial with a TCA (n=216) looked at desipramine. The dose was started low, and then titrated up to a dose recommended for the treatment of depression. (However, most trials used low doses of TCAs, and using antidepressant doses don’t appear to be necessary).2 The presence of depression did not predict a response to treatment for IBS symptoms. A high incidence of side effects resulted in a dropout rate of almost one-third of subjects.1
SSRIs have a better side effect profile than TCAs. Unlike TCAs, good evidence for efficacy in improving IBS symptoms from individual trials of SSRIs is lacking.1
The SSRIs have a prokinetic effect, so they might work better in patients with IBS-C. Since TCAs are more likely to cause anticholinergic side effects like constipation, they might be better for individuals with IBS-D.1 Experts say that TCAs might be best for improving pain.


Antispasmodics (e.g., dicyclomine [Bentyl-U.S., Bentylol-Canada], hyoscyamine [Levsin-U.S. only], hyoscine butylbromide [Buscopan-Canada only]) as a class can provide short-term relief of symptoms like abdominal pain and discomfort from IBS. The reason for this might be that pain with IBS is caused by colonic smooth muscle spasms.1
Systematic review (n=1,778) suggests that about one patient will have symptom relief for every five patients treated with an antispasmodic. However, most of the antispasmodics that have been studied for IBS are not available in the U.S. or Canada. In addition, studies typically have not specified the type of IBS treated.1
The most common side effects with antispasmodics are anticholinergic in nature. These include dry mouth, dizziness, and blurred vision. About one in 18 patients treated will experience a side effect, according to available data.
Limited data suggest that peppermint oil, thought to relax smooth muscle in the GI tract, might improve symptoms of IBS in about one out of three patients treated. Side effects reported in studies were rare.1
The usual dose of peppermint oil for adults with IBS is 0.2 to 0.4 mL given three times daily, in enteric-coated liquid-filled capsules.
Antispasmodics should be considered especially when IBS symptoms are exacerbated by meals. In this case, they can be taken about 30 minutes before a meal, on an as-needed basis.


Since patients with IBS-D have a faster colonic transit than healthy patients, drugs that slow colonic transit might be beneficial. There is some data on loperamide. Loperamide (Imodium, etc) doesn’t help for IBS symptoms like pain, but it does reduce frequency and improve stool consistency in almost all patients who are treated.1
Alosetron (Lotronex)
There’s good evidence that alosetron (Lotronex, available in U.S. only), a serotonin 5HT-3 antagonist, is better than placebo at improving IBS symptoms in patients with IBS-D.1,5
The majority of the body’s serotonin is found in the GI tract. Serotonin plays a major role in GI motor and secretory function and visceral sensation. Antagonism at the 5HT-3 receptor specifically delays GI transit, reduces colonic tone, decreases the gastrocolic reflex, and decreases visceral sensation.1
Data from eight placebo-controlled trials (n=5,000) show that about eight patients will need to be treated with alosetron for one patient to experience adequate relief from discomfort and urgency. However, alosetron has serious side effects that include constipation and colon ischemia. The number needed to harm (NNH) for one adverse event with alosetron is ten. About one patient for every 1,000 patient-years of alosetron treatment will have ischemic colitis.1
The benefit vs. risk is most favorable in women who have not responded to other therapies. Several years ago, alosetron was pulled from the market for a period of time. However, it was subsequently returned to the U.S. market, and has since been available through a special prescribing program for women with chronic, severe IBS-D who have failed other therapies.5
A 30-day supply of 1 mg twice daily of Lotronex costs over $1,000.
Tegaserod (Zelnorm)
Tegaserod (Zelnorm) is better than placebo at relieving IBS symptoms in women with IBS-C and IBS-M. However, cardiovascular events like stroke and heart attack are more common with tegaserod compared to placebo. It was withdrawn from the U.S. market in 2007.1
For a period of time, tegaserod was available through FDA under a treatment investigational new drug application (T-IND) protocol. However, it is no longer available under the T-IND, and is only available for emergency use in life-threatening situations.
Tegaserod is no longer available in Canada.
Lubiprostone (Amitiza)
Lubiprostone (Amitiza), available in the U.S. but not Canada, is more effective than placebo at relieving IBS symptoms in women with IBS-C. Its efficacy in men has not been conclusively demonstrated.6
Lubiprostone is derived from prostaglandin. It’s a C-2 chloride channel activator. Lubiprostone works topically from the luminal surface of the GI tract to promote chloride secretion into the intestine. Sodium then enters the lumen as a result of the negative charge of the chloride ions, and water follows passively.6
The most common side effects with lubiprostone are nausea, diarrhea, and abdominal pain. Lubiprostone is contraindicated in patients with mechanical bowel obstruction.6
Lubiprostone was first approved for the treatment of chronic constipation. The recommended oral dose for constipation is 24 mcg twice daily. Note that the dose of lubiprostone for IBS is lower, at 8 mcg twice daily.6
A 30-day supply of lubiprostone will cost cash-paying patients around $220.


Short courses of non-absorbable antibiotics are better than placebo for improving overall symptoms of IBS, and for reducing bloating specifically. There’s data for rifaximin (Xifaxan, available in U.S. only), with three RCTs (n=545) supporting its superiority over placebo. Duration of effect is variable. Symptom improvement can last after the antibiotic is stopped, for ten weeks or more in some cases. Most of the patients studied had IBS-D.1
Studies of rifaximin for IBS used higher doses than the FDA-approved dose for treatment of traveler’s diarrhea, which is 200 mg three times daily for three days. The dose of rifaximin studied for IBS was 1,100 to 1,200 mg divided two to three times daily for ten to 14 days.1
No severe adverse events were seen with these high doses of rifaximin. Two of the rifaximin studies reported individual side effects, and there was no significant difference between the rifaximin and placebo groups.


Nineteen trials evaluating the use of probiotics in IBS patients (n=1,668) were included in a systematic review. Eleven of these studies (n=936) looked at improvement in IBS symptoms as a dichotomous (benefit vs. no benefit) type of outcome. About one in four patients treated had symptom improvement. All of the different probiotics, including Lactobacillus, Bifidobacteria, Streptococcus, and combinations, showed a trend toward benefit.1
However, when the degree of improvement in IBS symptoms was considered as reported in fourteen trials (n=1,351), Lactobacillus did not have an effect on IBS symptoms. Probiotics with Bifidobacteria (e.g., Align, Activia, VSL #3 [all U.S. only]; Bifidox [Canada]) appear to be more effective.1 For more information about probiotics and their uses see our, “Comparison of Probiotic Products.”

Nondrug Therapies

Pooled data (n=1,278) show that psychological therapies (e.g., cognitive behavioral therapy, interpersonal psychotherapy, hypnotherapy) can improve overall symptoms of IBS. However, relaxation therapy alone does not offer any benefit. The mechanism for improvement of IBS symptoms might be stress reduction, empathic attitude of the provider, etc.1
There isn’t good evidence to support avoiding specific foods to help improve symptoms of IBS. However, the majority of patients relate symptoms to consumption of certain foods and as a result, avoid those foods. If this is the case, don’t discourage the patient unless exclusion of the particular food could lead to dietary deficiencies.


There are a wide variety of treatments for IBS, with varying degrees of effectiveness. Treatment decisions are often based on the severity of disease, and on the predominant IBS symptom of either constipation or diarrhea.3
For all patients with IBS, insoluble fiber like psyllium can be tried for regulating bowel movements and reducing pain.1 Be aware of the potential for gas and bloating. Introduce fiber gradually to minimize these side effects.1
Recommend antispasmodics or peppermint oil to reduce abdominal discomfort.1,2 Consider this especially for patients whose symptoms are worsened by meals.3 Antidepressants might also help with abdominal pain.1
Probiotics containing Bifidobacteria might help improve bloating and flatulence associated with IBS.1 SSRIs or TCAs can be tried for overall symptom improvement as well.1 Consider SSRIs for IBS-C, and TCAs for IBS-D.
Recommend loperamide to reduce the frequency of bowel movements for patients with IBS-D, but don’t expect it to help with abdominal cramping.1 Reserve alosetron (Lotronex) for women with severe IBS-D refractory to other therapies. It’s available through a restricted prescribing program because of the increased risk for ischemic colitis.1
Try osmotic laxatives like PEG for increasing stool frequency in patients with IBS-C.1 Reserve lubiprostone (Amitiza) for women with IBS-C who haven’t responded to other therapies. It’s prescription only and quite expensive.1
Psychotherapy can help improve symptoms of IBS, possibly by reducing stress.1 But relaxation therapy alone doesn’t offer any advantage over usual care.1
Project Leader in preparation of this Detail-Document: Stacy A. Hester, R.Ph., BCPS, Assistant Editor


1.Brandt LJ, Chey WD, Foxx-Orenstein AE, et al. An evidence-based systematic review on the management of irritable bowel syndrome. Am J Gastroenterol 2009;104:S1-S35.
2.Jellin JM, Gregory PJ, et al. Pharmacist’s Letter/Prescriber’s Letter Natural Medicines Comprehensive Database. http://www.naturaldatabase.com (Accessed April 15, 2009).
3.American Gastroenterological Association. American Gastroenterological Association medical position statement: irritable bowel syndrome. Gastroenterology 2002;123:2105-7.
4.Mertz HR. Irritable bowel syndrome. N Engl J Med 2003;349:2136-46.
5.Product information for Lotronex. Prometheus. San Diego, CA 92121. April 2008.
6.Product information for Amitiza. Takeda. Deerfield, IL 60015. April 2008.