A drug already used to treat that tourist nightmare — traveler's diarrhea — may also prevent it without causing the antibiotic resistance that can eventually make medicines ineffective, new research suggests.
The study showed that the antibiotic rifaximin prevented the troublesome condition in about 85 percent of the people who took it.
The experiment involved 210 American students studying Spanish in Guadalajara, Mexico, during the summer of 2003. Just under 15 percent of the students who took rifaximin for two weeks suffered from diarrhea, while nearly 54 percent of those who took placebos came down with the illness, which also includes nausea, vomiting and stomach pain.
Antibiotics have been used for years to treat traveler's diarrhea because it is caused by bacteria found in local food and water. Last year, the Food and Drug Administration approved rifaximin as a treatment for the illness.
But the study to be published Tuesday in the Annals of Internal Medicine suggests it's an effective preventive step as well.
"People who get decked all the time (by traveler's diarrhea) tend not to travel," said lead author Dr. Herbert DuPont, of the University of Texas Health Science Center in Houston and chief of internal medicine at St. Luke's Episcopal Hospital. "This would allow these people to enjoy a traveling life."
Traveler's diarrhea affects about 20 million international travelers a year, Herbert said. And about 40 percent of those have an extra genetic susceptibility that means they get no relief from over-the-counter treatments such as Pepto-Bismol.
Dr. Phyllis Kozarsky, a professor of medicine and infectious diseases at Emory School of Medicine in Atlanta, said doctors generally don't like to prescribe antibiotics as a preventive measure.
But, she said, rifaximin would be a good idea for people whose immune systems are compromised, who are traveling to developing countries for special events and can't afford the risk of being downed by diarrhea, and for people "who travel frequently to Mexico and once they get on the plane, think, 'Oh, gee, it's just a matter of time.'"
A future study will focus on Thailand, where the bacteria that can cause diarrhea is more invasive than that found in Mexico, Herbert said.
"We have every reason to think it'll work in Asia," he said.
While a germ can become resistant to an antibiotic that is overused, the researchers believe rifaximin has properties that make it unlikely to cause resistance.
Rifaximin is marketed by Salix Pharmaceuticals of Raleigh, N.C., under the name Xifaxan. Salix helped fund UT's study, and Herbert and some of his colleagues on the study have worked as consultants to the drug maker.