Antispasmodics relax the muscles of the intestine. A systematic review of published studies concluded that pain and well-being improves in half of users. However, many of these studies have not been well-designed and additional studies are necessary to draw reliable conclusions. Antispasmotics (bowel relaxants) are less effective for bloating than for pain.

Side effects are common including dry eyes and mouth, sleepiness, constipation, and difficulty passing urine. Side effects may be milder with the use of dicyclomine (Bentyl).

Antispasmotics should be used with caution in individuals with constipation.

These medications should not be taken on a daily basis but should only be used for situations that are known to trigger or provoke symptoms.

These medications are most effective if taken before meals.

Fiber makes hard stools softer, bulkier and easier to pass. Fiber can also absorb water and add form to loose stools.

Available studies suggest that fiber supplements are more effective for constipation than for diarrhea. Fiber may not have an effect on the abdominal pain of IBS.

Side effects include gas and bloating. Gradually increasing fiber can reduce these side effects. Synthetic fiber supplements (polycarbophil and methylcellulose) may cause less bloating.

Newer capsule and dissolvable (non-gritty) formulations may be more convenient.

Certain foods can worsen the symptoms of irritable bowel syndrome. However, foods do not cause IBS.

Avoidance of foods known to produce intestinal gas such as beans, carbonated beverages, and certain fruits and vegetables can reduce abdominal bloating and discomfort.

Some people cannot adequately digest lactose, the sugar in dairy products (lactose intolerance). Consuming dairy products (milk, yogurt, cheese) can then result in gas, bloating and/or diarrhea. Avoidance of dairy products in lactose-intolerant individuals may reduce or eliminate symptoms. If dairy is eliminated from the diet, a calcium supplement should be taken.

Caffeine and artificial sweeteners (sorbitol, fructose) can produce or worsen diarrhea.

Small studies suggest that a variety of psychosocial therapies including behavioral therapy (a type of "talking therapy" which teaches practical behaviors including social skills, self-control, and practical problem solving) may be beneficial for irritable bowel syndrome (IBS). Improvement in irritable bowel syndrome (IBS) frequently follows improvement in anxiety and depression. Behavioral or psychological therapies (counseling) may be expensive, time-consuming and require a level of committment.

Antidepressants can relieve pain as well as alter mood. Tricyclic agents are the best studied antidepressants in irritable bowel syndrome (IBS). These agents may be most effective at relieving pain. The doses used in irritable bowel syndrome (IBS) are generally lower than those used for depression. Several weeks may be needed before improvement is noted.

Common side effects of the tricyclics include drowsiness, dizziness, fatigue, dry mouth, and constipation. Tricyclics should be used with caution in individuals with pre-existing constipation to avoid exacerbating this problem.

Another type of antidepressant, the SSRI's (Prozac, Paxil, Zoloft, etc.) are less well studied for irritable bowel syndrome (IBS). Diarrhea is relatively common in those who are taking the SSRI's.

Antidiarrheals are used to treat diarrhea from a variety of causes including irritable bowel syndrome (IBS). Loperamide (Imodium) is the best studied and reduces diarrhea but not abdominal discomfort and bloating. Constipation is a major side effect.

Pepto-Bismol results in dark/black stools and should not be used if kidney function is abnormal.

Avoid anti-diarrhea drugs and seek medical attention if diarrhea is bloody or accompanied by a fever and/or abdominal pain.

Antidiarrheals are generally recommended on an as-needed, rather than a daily, basis.

Cholestryamine is primarily a cholesterol-lowering drug that is sometimes used for other conditions. It may be used to treat diarrhea occurring after removal of the gall bladder. It can also improve diarrhea due to a variety of other causes including irritable bowel syndrome (IBS), though it has not been well-studied for this condition.

Cholestryamine is usually taken at meals, but should be taken several hours apart from other medications because it can affect their absorption into the digestive system and, therefore, their effectiveness.

The dose of cholestryamine may need to be adjusted to avoid constipation.

The gritty texture may be unappealing to some.

Lotronex (alosetron) improves diarrhea and abdominal pain in approximately 40% of women with irritable bowel syndrome (IBS). Studies did not find a reduction in bloating. Lotronex has not been well-studied in men with IBS.

Serious constipation-related complications and ischemic colitis (damage to the intestines due to low blood flow) have been reported with this medication. Initially, this medication was removed from the market. It is now available only from specially-trained doctors and only for women with severe diarrhea and IBS who have failed other therapies; who are also at low risk of complications (those who don't have vascular/blood vessel disease or diabetes).

Other medications of the same class as Lotronex are commonly used to treat severe nausea but are not currently used for irritable bowel syndrome (IBS).

Many laxatives are available over-the-counter. Laxatives have not been well-studied in irritable bowel syndrome (IBS) but are known to improve constipation. These medications may have less of an effect on abdominal pain. Certain types of laxatives are safer for long-term use while others are only recommended for a short duration. See the "Constipation" Quicklook for laxative comparisons.

Tegaserod (Zelnorm) is a medication that has been effective for some people with Irritable Bowel Disease. Until recently, it was primarily prescribed for women for brief periods of time. The drug was recently taken off the market by the drug manufacturer because there was evidence that it might increase the risk of serious side effects including heart attack, stroke, and angina (heart-related pain that can lead to a heart attack). This increased risk seems to mostly affect people who have heart disease.

Prokinetics increase the force of the intestinal muscles and stimulate intestinal movement. These medications are mostly used for people with symptoms such as nausea and inability to eat adequate amounts due to a sensation of abdominal fullness. They may result in diarrhea. Other common side effects include dry mouth, drowsiness, agitation and stiff movements.

Domperidone is available in Canada but not in the US, and may have fewer side effects. A recent small study showed it to be no more effective than placebo (fake pills). Cisapride was a prokinetic available in the past. This agent was removed from the market due to serious side effects, but may be available to your physician for compassionate use only, in rare cases, directly from the manufacturer. People taking this drug are at increased risk of developing a serious irregular heart rhythm called "Torsade de Pointes" and should be followed closely with EKG (electrocardiogram) monitoring.

Metoclopramide can cause a serious side effect called "Tardive Dyskinesia" (involuntary uncontrollable jerking movements of the face, trunk and limbs) and is not recommended.

A few small studies suggest that antibiotics may be helpful for some individuals with irritable bowel syndrome (IBS). More studies are needed before these medications can be routinely recommended for IBS. A recent study showed some benefit for an antibiotic, Rifaxamin (Xifaxan), that stays in the intestine and does not get into the bloodstream.

There is concern that antibiotic resistance (failure of antibiotics to work against infections) will develop with overuse of these medications.

Common side effects of antibiotics are rash, stomach upset, diarrhea, and others.