Synopsis

Rifaximin (Xifaxan) is a nonabsorbed antibiotic for the treatment of adult traveler's diarrhea caused by enterotoxigenic strains of Escherichia coli. It is not effective for diarrhea with fever or blood in the stool or diarrhea caused by Campylobacter jejuni.

Safety

Rifaximin is minimally absorbed (less than 4 percent), making systemic effects unlikely. It has not been found to interact with drugs metabolized by the microsomal cytochrome P450 isoenzyme system.¹ Rifaximin is contraindicated in patients who are allergic to rifampin (Rifadin) because it is structurally related to rifampin and has caused skin reactions in sensitive patients.¹ Rifaximin is pregnancy category C. It has not been studied in children younger than 12 years.

Tolerability

Rifaximin is well tolerated. In clinical studies the dropout rate caused by adverse effects was 1 percent.² Adverse effects such as headache, abdominal cramps, flatulence, constipation, nausea, and vomiting are difficult to separate from the symptoms of traveler's diarrhea.^2,3

Effectiveness

A randomized controlled trial³ involving travelers to Mexico or Kenya who had acute traveler's diarrhea showed that dosages of 600 and 1,200 mg rifaximin daily were more effective than placebo. Rifaximin reduced the median interval from initiation of therapy to passage of the last unformed stool by approximately one half (33 hours in both rifaximin groups compared with 60 hours in the placebo group).³ In another study,² rifaximin (400 mg twice daily) was found to be as effective as ciprofloxacin (Cipro; 500 mg twice daily) in relieving symptoms of traveler's diarrhea. When therapy was initiated after 24 hours of symptoms, diarrhea ceased in an average of one day with rifaximin and ciprofloxacin compared with an average of three days for placebo.² Rifaximin is less effective if E. coli is not the predominant pathogen. It has not been compared with other fluoroquinolones or bismuth subsalicylate (Pepto-Bismol) for treatment of traveler's diarrhea.

One published study ⁴ has evaluated rifaximin as a preventive therapy. In this trial, 210 college students traveling to Mexico were randomly assigned to receive rifaximin at dosages of 200 mg once, twice, or three times daily or placebo for two weeks.⁴ Diarrhea developed in 15 percent of participants receiving rifaximin compared with 54 percent of the placebo group (number needed to treat = 2.5).⁴ The cost for two weeks of prophylactic treatment would be approximately $50 to $150, and such usage is not currently approved by the U.S. Food and Drug Administration. Rifaximin has not been compared with other preventive treatments.

Price

A three-day supply of rifaximin (three 200-mg tablets daily) is similar in price to a three-day course of ciprofloxacin, costing around $32.

Simplicity

Rifaximin should be taken three times daily, without regard to meals, for three days. Ciprofloxacin is administered twice daily for three days.

Bottom Line

Rifaximin is safe and effective for treatment in most patients with traveler's diarrhea, but it offers no advantages over ciprofloxacin. At the same cost, it has a less convenient dosage interval than ciprofloxacin and has more limitations.