STORY BY:

Scott Merville

This summer, your south-of-the-border vacation may not have to be sidelined by stomach upset and diarrhea. In fact, you may not have to wait for symptoms to appear at all.

An antibiotic can be safely used to prevent attacks of diarrhea that plague millions of globe-trotting vacationers and business travelers, a Houston research team reports this week in the Annals of Internal Medicine.

“Our findings show that rifaximin is an ideal drug for prevention of travelers’ diarrhea, an illness that affects an estimated 20 million international travelers each year,” says lead author Herbert DuPont, M.D., director of the Center for Infectious Diseases at the University of Texas School of Public Health at Houston and chief of internal medicine at St. Luke's Episcopal Hospital.

“This medication's effectiveness, lack of side effects, and its ability to avoid development of resistant strains of bacteria will allow us to change the way we manage this disease,” DuPont says.

The clinical trial studied 210 U.S. students studying Spanish in Mexico during the summer of 2003. Only 14.74 percent of those who took a daily dose of rifaximin for two weeks suffered from diarrhea, while 53.7 percent of those who took placebos came down with the illness, which also includes nausea, vomiting and stomach pain.

No danger of antibiotic resistance

Travelers’ diarrhea has been treated for years by antibiotics because it is caused by bacteria found mainly in local food. DuPont's group previously showed that rifaximin is safe and effective therapy for the illness in studies carried out in Mexico, Peru, India and Kenya.

Originally an Italian drug, the antibiotic has been available in Europe and elsewhere for years to treat diarrhea. The U.S. Food and Drug Administration approved the antibiotic for treatment of traveler's diarrhea a year ago.

But would the treatment also prevent the whole unpleasant experience? And, more importantly, would it do so without provoking development of a drug-resistant response by the targeted bacteria?

This last point is crucial, DuPont says, because using other antibiotics such as Cipro as a broad preventive measure would hasten development of bacterial resistance, reducing the future value of the antibiotic to treat pneumonia and other life-threatening diseases.

Lab analysis in the study showed rifaximin did not stimulate resistance in the Escherichia coli (E. coli) bacteria that causes the illness in Mexico, a finding consistent with earlier studies. Unlike other antibiotics, which are absorbed and dispersed throughout the body, rifaximin lingers almost exclusively in the gastrointestinal tract, limiting its ability to stimulate resistance.

Co-author Charles Ericsson and travel medicine expert at UT Medical School says the very fact that it is non-absorbable is also what makes it safe for children and pregnant travelers. However, by its very nature, it will not be useful for other diseases, like pneumonia, that need the absorbability factor.

“It matches well with the profile for travelers,” Ericsson says.

Researchers are following up with studies of the drug in Asia, where travelers’ diarrhea is caused by other bacteria, such as Shigella, Salmonella and Campylobacter. And they are following up an earlier finding that 10 percent of those who get traveler's diarrhea develop the more serious irritable bowel syndrome. “If it is found that this drug prevents irritable bowel syndrome, then rifaximin prevention of travelers’ diarrhea will go from a good idea to a critical health safeguard,” DuPont says.

UPDATED: 5-20-2005

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