Best Evidence Analyses and Commentary

New drug approved for C. diff
Gabriella Lucarelli, PharmD Candidate, 2012

On May 27, 2011 the FDA announced approval for Dificid (fidaxomicin), a new macrolide antibiotic for the treatment of Clostridium difficile (C. diff) [1] .

In a head-to-head, non-inferiority trial with oral vancomycin (125 mg) four times a day for ten days, Dificid was found to be non-inferior to vancomycin.  This study also concluded that Dificid was superior to vancomycin at sustained clinical response at the end of a 4 week follow-up [2], [3].

The treatment course of Dificid is one (1) 200 mg tablet by mouth twice a day for ten days [1].  The main side effects of Dificid are: nausea, vomiting and upset stomach.  Dificid and its main metabolite are substrates for the PGP efflux transporter.  Any inducers or inhibitors of PGP will affect the level of drug [4] . To prevent resistance emerging to Dificid it is only indicated when the infection has been proven or strongly suspected to be caused by C. diff [1].

The new drug comes at a good time to offer clinicians an additional treatment option as a number of C. diff strains with decreased susceptibility are emerging. Pelaez and colleagues reported that 26 of 415 tested strains of C.diff  had decreased susceptibility to metronidazole. Thirteen of the 415 tested isolates had decreased susceptibility to vancomycin.  The highest rate of susceptibility came from HIV infected patients in both cases [5].     


1.        "FDA Approves Treatment for Clostridium Difficile Infection." U S Food and Drug Administration Home Page. US Department of Health and Human Services, 27 May 2011. Web. 08 Aug. 2011.

2.        "Dificid: 14 Clinical Studies." New Drug Review: Original New Drug Approvals. 1 June 2011. Web. 8 Aug. 2011.

3.        Louie, Thomas J., Mark A. Miller, Kathleen M. Mullane, et. al. "Fidaxomicin versus Vancomycin for Clostridium Difficile Infection." NEJM. 3 Feb. 2011. Web. 8 Aug. 2011.

4.        "Dificid (fidaxomicin)." DailyMed. NIH, May 2011. Web. 08 Aug. 2011.

5.        Shah, Dhara, Minh-Duc Dang, Rodrigo Hasbun et. al. "Clostridium Difficile Infection: Update on Emerging Antibiotic Treatment Options and Antibiotic Resistance." Expert Review of Anti-Infective Therapy 8.5 (2010): 555-64. Print.

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