Antidiarrheal agents, specifically loperamide or diphenoxylate, are often useful in patients with mild disease. The goal is to reduce the number of bowel movements and help to relieve rectal urgency. Anticholinergics including hyoscyamine and dicyclomine hydrochloride often are helpful. Powder opium, an antidiarrheal, combined with an antispasmodic (belladonna alkaloid), is another option for refractory disease. Antispasmodic agents have anticholinergic agents as the primary ingredient, and compliance may be a problem because side effects include dry mouth, visual disturbances, and constipation. These agents can precipitate toxic megacolon, which may result in severe colitis. Toxic megacolon is a medical and potential surgical emergency, in some cases requiring colectomy. Even though these patients may be extremely difficult to treat, judicious use of symptom-based pharmacologic approaches, reassurance, and patient insight may be helpful. The quality of life for some individuals with IBS is extremely compromised, requiring intense counseling. It may be difficult to treat them in a busy primary care practice. Those with a concurrent psychiatric disease, such as depression, will often benefit from psychiatric consultation and pharmacologic treatment of the underlying disease in the overall management.
Individuals with chronic, debilitating irritable bowel syndrome should be referred to a gastroenterologist. Any suspicion of organic disease with systemic changes, including weight loss and bloody diarrhea, should be considered for referral.
Studies suggest a relationship between IBS symptoms and an imbalance of central nervous system neurotransmitters related to stress in the environment (58,59). Serotonins (5hydroxytryptamine or 5-HT) are important in the development of gut disorders. Only 5% of total body serotonin is found in the central nervous system, while 95% is found in the gastrointestinal tract. Other neurotransmitters associated with gastrointestinal disorders include calcitonin, neurotensin, substance P, nitric oxide, vasoactive intestinal peptide, and acetylcholine. These neurotransmitters function at the level of the bowel and the central nervous system.
Several compounds were studied that interact with serotonin receptors in the bowel (5 HT-3 and 5 HT-4). The 5-HT-3 antagonist, alosetron, was introduced to treat patients with diarrhea. Patients with other symptoms, including alternating diarrhea and constipation, and individuals with primary constipation received the drug, resulting in severe constipation in approximately one-third of patients. There were reports of ischemic colitis with the use of this drug. Although the drug was withdrawn for a time period, the U.S. Food and Drug Administration allowed its reintroduction. Tegaserod is a 5-HT-4 receptor (serotonin receptor) agonist that is approved for short-term use in patients with constipation. It has gastrointestinal stimulatory effects facilitated by intercolonergic transmission as its primary mode of action. There are many 5-HT drugs under development that will be introduced over the next 2 to 5 years.
The term gastroesophageal reﬂex disease (GERD) is a commonly used label for many forms of indigestion and heartburn. The American College of Gastroenterology defines it as symptoms or mucosal damage produced by the abnormal reﬂux of gastric contents into the esophagus (60). The term “abnormal” is key because some reﬂux is physiologic, usually occurring postprandial and typically being asymptomatic. Given the variation in definition, its prevalence is hard to determine, but it is clear that GERD is more common in the Western world.