It is not clear what causes irritable bowel syndrome, or IBS, but certain factors seem to make some people more vulnerable than others. Risk factors for IBS include:
Sex. About twice as many women as men suffer from IBS, reports the American College of Gastroenterology. Researchers aren't sure why this is so, but they suspect that changing hormones in the female menstrual cycle may have something to do with it.
Age. IBS can affect people of all ages, but it is more likely to occur...
This all makes it difficult for researchers to find a single drug treatment that will relieve all the symptoms of IBS. Different medications work for IBS with constipation and for IBS with diarrhea. Doctors will usually tailor an individual treatment regimen for people who have IBS with alternating symptoms.
People with alternating IBS symptoms should not try to treat themselves, says J. Patrick Waring, MD, a gastroenterologist at Digestive Health Care of Georgia.
"They should not take something for their constipation on their own, and then when they get diarrhea, take something for their diarrhea, and go back and forth," he says. "That can actually exacerbate the problem."
J. Patrick Waring, MD, gastroenterologist, Digestive Health Care of Georgia.
Medscape.com: "Diagnosis, Pathophysiology, and Treatment of Irritable Bowel Syndrome," and "Consensus Report: Clinical Trial Guidelines for Pharmacological Treatment of Irritable Bowel Syndrome."
American College of Gastroenterology.