1. Irritable Bowel Syndrome (IBS) Slideshow Pictures
2. Digestive Disease Myths Slideshow Pictures
3. Diverticulitis (Diverticulosis) Slideshow Pictures

Medical Author:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Medical Editor:

Bhupinder Anand, MD

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Irritable bowel syndrome (IBS) facts
• What is irritable bowel syndrome (IBS)?
• What causes irritable bowel syndrome (IBS)?
• What are symptoms of irritable bowel syndrome (IBS)?
• What are the complications of irritable bowel syndrome (IBS)?
• How is irritable bowel syndrome (IBS) diagnosed?
• How is irritable bowel syndrome (IBS) treated?
• Constipation medications
• Diarrhea medications
• Abdominal pain medications
• Psychotropic drugs
• Psychological treatments
• IBS Diet
• Is there a relationship between IBS and small intestinal bacterial overgrowth?
• What is a reasonable approach to irritable bowel syndrome (IBS)?
• What is in the future for irritable bowel syndrome (IBS)?
• Patient Comments: Irritable Bowel Syndrome - Diagnosis
• Patient Comments: Irritable Bowel Syndrome (IBS) - Treatments
• Patient Comments: Irritable Bowel Syndrome (IBS) - Symptoms
• Find a local Gastroenterologist in your town
• Irritable Bowel Syndrome Index

The most widely studied drugs for the treatment of abdominal pain are a group of drugs called smooth-muscle relaxants.

The gastrointestinal tract muscle is composed of a type of muscle called smooth muscle. (By contrast, skeletal muscles, such as the biceps, are composed of a type of muscle called striated muscle.) Smooth muscle relaxing drugs reduce the strength of contraction of the smooth muscles but do not affect the contraction of other types of muscles. They are used in IBS with the assumption (not proved) that strong or prolonged contractions of smooth muscles in the intestine-spasms-are the cause of pain in IBS. There are smooth muscle relaxants that are placed under the tongue, like nitroglycerin for treatment of angina, so that they may be absorbed rapidly. Smooth muscle relaxants are approximately 20% more effective than a placebo in reducing abdominal pain. It is not clear if smooth muscle relaxants have a beneficial effect on constipation or diarrhea.

Some commonly used smooth muscle relaxants are hyoscyamine (for example, Levsin) and methscopolamine (for example, Pamine). Other drugs combine smooth muscle relaxants with a sedative (for example, hyoscyamine sulfate, atropine sulfate, scopolamine sulfate and phenobarbital [Donnatal]), but there is no evidence that the addition of sedatives adds to the efficacy (effectiveness) of the treatment.

Patients with IBS are frequently found to be suffering from depression, but it is unclear if depression is the cause of IBS, the result of the IBS, or unrelated to the IBS. Several trials have shown that antidepressants are effective in IBS in relieving abdominal pain and, perhaps, diarrhea. The antidepressants work in IBS, however, at relatively low doses that have little or no effect on depression. It is believed therefore, that they are working not by combating depression, but in different ways (through different mechanisms). For example, these drugs have been shown to adjust (modulate) the activity of nerves and to have analgesic (pain-relieving) effects as well. Commonly used psychotropic drugs include the tricyclic antidepressants, amitriptyline (Elavil, Endep), desipramine (Norpramine), and trimipramine (Surmontil). Although studies are encouraging, it is not yet clear whether the newer class of antidepressants, the serotonin-reuptake inhibitors, such as fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil) are effective.