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New Oral Antibiotic Superior to Oral Vancomycin in Controlling C Difficile Diarrhea

Fidaxomicin is superior to vancomycin in treating recurrences of gastrointestinal Clostridium difficile infection, according to a blinded randomized trial presented here at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

"Over 20 years, vancomycin has been the best drug for efficacy [in the treatment of C difficile infection. The problem is that the recurrence rate in sick people, like those we included in the study, is about 30%. Now we know we can prevent recurrences after vancomycin with fidaxomicin. Fidaxomicin was also superior as first-line treatment in phase 3 studies. In my view, this is a dramatic change," said Oliver A. Cornely, MD, from the University Hospital of Cologne in Germany.

Fidaxomicin is a first-in-class oral macrocyclic antibiotic developed by Optimer Pharmaceuticals. The drug has a narrow spectrum of activity against normal gut flora, with potent bactericidal activity against C difficile. It attacks the pathogenic bacteria while sparing normal protective gastrointestinal flora. In contrast, vancomycin, which is approved for this indication, and metronidazole, which is often used as treatment, suppress the growth of normal endogenous flora.

The study presented at ICAAC focused on a prespecified nested population of 178 patients with a first recurrence within 90 days of a previous episode. Patients were then randomized to receive either fidaxomicin or vancomycin. These 178 patients came from 2 randomized phase 3 trials of 1164 patients with acute C difficile infection. In both phase 3 trials, fidaxomicin was noninferior to oral vancomycin in preventing symptom recurrence within 30 days of completing 10 days of therapy.

Recurrence was defined as 3 or more unformed bowel movements in the 24 hours prior to randomization and the presence of C difficile toxin A or B in the stool within 48 hours of randomization; this definition was used in the original phase 3 trials and in the nested trial.

For 10 days, patients received oral fidaxomicin 200 mg twice daily or oral vancomycin 125 mg 4 times daily. More than 90% of both groups responded to initial therapy in the phase 3 trials.

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