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Irritable Bowel Syndrome: An MD’s Perspective Symptoms, Diagnosis, and Treatment

Irritable Bowel Syndrome (IBS) is the most commonly diagnosed gastrointestinal condition in this country, estimated at 10-15 % of the population, with a 2:1 female predominance. IBS is a group of symptoms without a known cause. The current medical criteria are chronic abdominal pain and altered bowel habits, lasting at least three months, without a verifiable diagnosis (e.g. appendicitis, ulcerative colitis, diverticulitis).

There are two diagnoses that should be ruled out from IBS. The first is celiac sprue, due to gluten sensitivity, a protein found in wheat, barley and rye. The diagnosis is suspected with positive blood tests (IgA anti-tissue transglutaminase and IgA endomysial antibody) and confirmed with small bowel biopsy, both while on a high-gluten diet. The second is lactose intolerance and the diagnosis can be suspected with a lactose absorption test or lactose breath hydrogen test. I recommend a trial of gluten and lactose avoidance before making the diagnosis of IBS.

The pain is usually described as crampy or gassy of variable intensity with periodic exacerbations. Diverse upper gastrointestinal symptoms are common. Altered bowel habits are always present, but of no specific type, ranging from diarrhea to constipation to both. Weight loss, rectal bleeding and pain that awaken the patient from sleep are very uncommon. There is no known cure for IBS.

Non-pharmacologic treatment is often more effective than prescription drugs. The establishment of a therapeutic physician-patient relationship is a critical component of care. Next is dietary modification, especially avoidance of carbohydrates. The role of fiber supplementation is controversial, and there is no reliable way to diagnose food allergies. Increased physical activity has been suggested as helpful but the research evidence is weak.

Drugs are only an adjunct to treatment, and the choices vary widely depending upon the symptoms. Chronic use of drugs is discouraged because of the lifelong nature of IBS and the lack of convincing long term benefit. Also, the placebo effect confuses matters.

The most common drug categories include:

Antispasmodics–Dicylomine (Bentyl), hyoscyamine alone (Levsin) or with belladonna and phenobarbital (Donnatal) are sometimes helpful. Peppermint oil is an anti-spasmodic and is discussed by Dr. Sinsheimer.

Antidepressants–Tricyclic agents (e.g., Elavil, Tofranil, Pamelor, Norpramin) have some evidence of benefit, given at doses less than for depression. However, side effects limit their use, particularly constipation. The results with SSRIs (e.g., Prozac, Zoloft, Paxil) are inconsistent.

Benzodiazepines–These drugs (e.g., Xanax, Valium, Ativan) are of limited value, except for the short term therapy of acute situational anxiety that may be contributing to symptoms.

Antibiotics–Rifaximin (Xifaxan) is the only antibiotic reported to be effective, and should only be considered in patients with constipation after failure of other treatments.

Others–Information is sketchy (lubiprostone (Amitiza) or the drug is not available in the U.S. (linaclotide, ketotifen, tegaserod (Zelnorm)), or has severe side effects leading to very tight FDA control (alosetron (Lotronex)).

Patients with IBS should establish a good relationship with their doctor, try non-pharmacologic therapy first, and use prescription medications only with severe and prolonged symptoms.

Dr. Thomas Reynolds is a board-certified internist and oncologist. His practice focuses on integrative and comprehensive medical care, particularly for older adults. Dr. Reynolds can be reached at 760.773.3200 

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