Fidaxomicin: a new macrocyclic, RNA polymerase-inhibiting antibiotic for the treatment of Clostridium difficile infections.

Clostridium difficile infection is now a major concern throughout the developed world and its occurrence is a consequence of broad-spectrum antibiotic therapy primarily in the elderly in-patient population and high spore loads in hospitals in these regions. With the emergence of a hypervirulent, endemic strain, more severe disease is being recognized and is occurring in previously considered unusual patient groups. Vancomycin and metronidazole are the current mainstays for therapy of severe and nonsevere disease, respectively. Relapse is a major concern, with treatment options for these cases often difficult. Any new drug must be better than vancomycin for severe disease with fewer relapses. Fidaxomicin, a macrocyclic RNA polymerase inhibitor, has a narrow spectrum of activity, which is almost C. difficile specific. This drug appears to have a higher clinical cure rate than vancomycin, and fewer patients relapse following initial treatment. From the results of a recent Phase III trial, fidaxomicin appears to be an extremely promising drug for treating C. difficile infection and preventing relapses.