Rifaximin is a rifamycin antibacterial that irreversibly binds to the beta subunit of RNA-polymerase, inhibiting the synthesis of bacterial RNA. Less than 1% of the dose is absorbed from the GI tract, resulting in negligible plasma levels (<10 nanogram/ml).1
The efficacy of rifaximin for treating non-invasive travellers’ diarrhoea was established in 2 randomised, double-blind studies: rifaximin was compared with placebo in the first study2 and with ciprofloxacin or placebo in the second.3 In both studies, time to last unformed stool (TLUS) was used as the primary efficacy endpoint.
In the first study (n=380), rifaximin 200mg 3 times daily for 3 days was compared with placebo. Median TLUS was significantly shorter in the treatment arm than in the placebo arm (32.5 hours vs 60.0 hours; p=0.0001).2
In the second study (n=399), the median TLUS for patients treated with rifaximin 200mg 3 times daily for 3 days was less than half that of the placebo group (32.0 hours vs 65.5 hours; p=0.001). Additionally, rifaximin demonstrated non-inferiority to ciprofloxacin 500mg twice daily for 3 days (28.8 hours; p=0.35).3
Owing to the poor systemic absorption of rifaximin, adverse effects are restricted to headache and gastrointestinal disturbances including abdominal pain, nausea and diarrhoea. However, in both studies the adverse event profile in the rifaximin group did not significantly differ from that observed in the placebo groups.1-3
- Xifaxanta Summary of Product Characteristics, June 2011.
- Steffen et al. Am J Gastroenterol 2003; 98: 1073–8.
- Taylor DN et al. Am J Trop Med Hyg 2006; 74: 1060–6.
Further information: Norgine Pharmaceuticals Ltd