Fidaxomicin: the newest addition to the armamentarium against Clostridium difficile infections.

BACKGROUND: Fidaxomicin, a macrolide antibiotic, was the first medication for the management of Clostridium difficile infections (CDI) to be approved by the US Food and Drug Administration in more than 20 years.

OBJECTIVE: This article reviews published literature on fidaxomicin for management of CDI, including its chemistry, spectrum of activity, pharmacokinetic properties, pharmacodynamics, therapeutic efficacy, adverse events, dosing, administration, and pharmacoeconomic considerations.

METHODS: Pertinent English-language literature was reviewed through searches of MEDLINE, EMBASE, and BIOSIS from 1975 through September 2011. Reference lists of identified publications and published abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy meetings were also reviewed. Search terms included, but were not limited to, fidaxomicin, difimicin, lipiarmycin, tiacumicin B, OPT-80, Clostridium spp, and diarrhea.

RESULTS: A total of 79 publications were identified and 10 were excluded; 6 review articles and 4 abstracts that were later published as articles. Fidaxomicin's in vitro profile is favorable compared with oral metronidazole and vancomycin, with minimum inhibitory concentrations against C difficile that are 2 dilutions lower. From the 2 published Phase III trials, fidaxomicin was deemed to be noninferior in the treatment of mild to moderate CDI compared with oral vancomycin. Recurrence rates for all strains of CDI were lower with fidaxomicin than vancomycin. Adverse events associated with fidaxomicin were similar to placebo, with nausea and vomiting being the most common. Although no pharmacoeconomic studies have compared fidaxomicin with metronidazole or vancomycin, the current price exceeds $2500 (US) per treatment course.

CONCLUSIONS: Reports suggest that fidaxomicin is noninferior to oral vancomycin in the treatment of mild or moderate CDI, although no published comparisons with metronidazole exist to date. Additionally, fidaxomicin improved outcomes compared with oral vancomycin in terms of rates of relapse and recurrent CDI, and in patients who might require concomitant antibiotics. Prospective, randomized studies comparing fidaxomicin with metronidazole in the treatment of mild or moderate CDI, as well as against vancomycin for severe CDI, should be undertaken to clarify the exact role of fidaxomicin in clinical practice.