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Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Rifaximin Therapy for Irritable Bowel

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Chemical structure of rifaximin. Chemical structure of rifaximin.Outdoor activities, particularly those that involve foreign (outside the United States) travel, and even more particularly those in underdeveloped countries, can be interrupted with unpleasant diarrhea. The most common causes are infectious (i.e., viral, bacterial, or parasitic), but there are other causes. One frequent cause of abdominal pain and bowel dysfunction, commonly attributed to emotional stress, is irritable bowel syndrome.

Irritable bowel syndrome (IBS, sometimes called spastic colitis, nervous colon, or irritable colon) is characterized by abdominal distention, the passage of flatus, cramping (pain) relieved by defecation, onset associated with change in frequency and/or form of the stool, and mucus-laden diarrhea. This can be debilitating. The sufferer may also complain intermittently of constipation. The onset of IBS is often associated with a change in the form of the stool (commonly loose or watery, but sometimes very hard pellets). It is more common in women than in men, and can be triggered by psychological stress. Many sufferers carry their own antidiarrheal or antispasmodic medication, such as loperamide (Lomotil), or clidinium bromide with chlordiazepoxide (Librax). Constipation may be treated with laxatives, such as lactulose or polyethylene glycol solution. Drugs that diminish hyperactivity of the bowel include dicyclomine hydrochloride and hyoscyamine sulfate. Diarrhea may be treated with loperamide. Alosteron is used only for severe diarrhea-predominant IBS that does not respond after six months to conventional therapies.

Irritable bowel is a diagnosis of exclusion that should be made by a physician. If a person is known to suffer from IBS with a constipation component, she or he should be encouraged to eat adequate fiber (indigestible plant carbohydrate: bran, steamed vegetables, or 20 to 30 grams of fiber supplement) and avoid coffee (and other caffeinated beverages), alcohol, fatty foods, and gas-producing vegetables. A useful prophylactic measure may be regular ingestion of a probiotic (e.g., Lactobacillus or Bifidobacterium infantis 35624) preparation. Regular exercise also appears to be helpful for some individuals. There are numerous therapies under investigation for persons with IBS that is refractory to all of these measures. These include antidepressants, serotonin-3 and serotonin-4 receptor antagonists, antibiotics, herbal therapy (including peppermint oil), and other agents to reduce the sensitivity and motility of the bowel.

With regard to antibiotics, an important article was recently published. Mark Pimentel MD and his colleagues published “Rifaximin Therapy for Patients with Irritable Bowel Syndrome without Constipation” in the New England Journal of Medicine 2011;364:22-32. The thesis of their investigation was that there has been evidence to suggest that the bacteria that inhabit and grow in the human digestive tract may play an important role in the abnormal physiology of IBS. So, they decided to evaluate rifaximin, a minimally absorbed (through the gut) antibiotic, as treatment for IBS. Rifaximin is an antibiotic that has shown effectiveness and great promise as a relatively new therapy for diarrhea, such as the “traveler’s diarrhea” that is caused by certain bacteria (including Escherichia coli).

In this study, patients who had IBS without constipation received either rifaximin in an oral dose of 550 milligrams, or they received a placebo (a pill with no active ingredient) three times daily for two weeks, and then were followed for an additional 10 weeks. The participants were evaluated for relief of all IBS symptoms, and also in particular for relief of IBS-related bloating. The results showed that significantly more participants in the rifaximin group than in the placebo group had adequate relief of global IBS symptoms during the first four weeks after treatment, as well as adequate relief of bloating and improvement in abdominal pain and stool consistency. The incidence of adverse effects was similar in each group.

This is a promising therapy, but this study did not look at the question of whether or not it is a therapy that can be repeated at frequent intervals, as can other (i.e., non-antibiotic) therapies that don’t have an impact on the types of bacteria that grow in the bowel. So, until a general clinical recommendation from experts is derived from this information, for the outdoor traveler, it should be considered preliminary information.

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About the Author

Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.

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