New antibiotic may thwart travelers' tummy troubles

Prescribing a newer antibiotic that only acts in the gut may prevent cases of the dreaded diarrhea that frequently strikes people who travel to less-developed countries -- and it might achieve this end without the adverse events associated with broader-spectrum drugs, according to a study published in the May 17 Annals of Internal Medicine.

"It's very effective," said Herbert L. DuPont, MD, lead author and chief of internal medicine at St. Luke's Episcopal Hospital in Houston. "And there are no reported side effects."

Researchers randomized 210 American students attending a course in Guadalajara, Mexico, to receive, beginning upon arrival, two weeks of twice-daily doses of rifaximin, three-daily doses or a placebo. Rifaximin is a nonabsorbable antibiotic approved by the Food and Drug Administration in May 2004 for treatment of travelers' diarrhea.

Overall, only about 15% of those who took it developed symptoms, while about 54% in the placebo arm did. Also, those who took the medication and did not develop travelers' diarrhea were less likely to have other related intestinal problems, and any such complaints tended to be more mild. The conclusion: This drug may be a good choice for prevention as well as treatment.

What about resistance?

"It would be wonderful to be able to use a nonabsorbable antibiotic that doesn't tend to interact with other medications and has a low side-effect profile for prophylaxis," said Phyllis Kozarsky, MD, professor of medicine and infectious disease at Emory University School of Medicine in Atlanta.

Several travel medicine experts, however, expressed significant concern about the possible impact of having millions of people -- the multitudes who travel from industrialized counties to less-developed areas of the world every year -- using rifaximin. Prophylactic treatment for travel diarrhea is not a new idea, but has long fallen out of favor because, with such widespread utilization, several antibiotics used for serious conditions lost their power.

"We are talking 50 million potential users per year. This is a huge number of people," said Sherwood Gorbach, MD, professor of community health and medicine at Tufts University School of Medicine in Boston who wrote an accompanying, highly critical editorial. "It's safe to predict that, if it were to be released in this quantity, in a relatively short time resistance would develop."

The authors maintain, though, that resistance should be less important for this drug, because it's not used to treat more serious conditions. Also, unlike antibiotics previously used for prevention, it has no impact outside of the gut.

"Who cares if it develops resistance?" asked Dr. DuPont, who is also director of the Center for Infectious Diseases, University of Texas, Houston School of Public Health. "It's not going to promote resistance systemically, and this class has no value in other intestinal infections. We're not talking about a drug that's needed to treat pneumonia."

Another worry expressed by travel medicine experts is that, if given a prophylaxis, travelers would fail to take other necessary dietary precautions that could protect them against pathogens that this drug does not.

"People may have a false sense of security by taking an antibiotic and may not be as careful," said Gregory Juckett, MD, MPH, associate professor of family medicine at West Virginia University and coordinator of the institution's travel clinic.

Experts also questioned why a pharmacologic prophylaxis was necessary when the problem usually takes the form of a minor inconvenience treated quickly with available medications.

"I don't think it's justified," Dr. Gorbach said. "We have very rapid treatments, so you don't have to suffer that long."

Researchers responded that it was not clear that travelers' diarrhea is always such a benign self-limiting condition because some evidence suggests that it may be linked to the development of more serious gastrointestinal troubles, such as irritable bowel syndrome.

The authors plan to investigate further whether this strategy can prevent the condition and whether it will work for travelers going to other parts of the world.