FDA Approves Fidaxomicin for the Treatment of C Difficile

May 27, 2011 ( UPDATED May 31, 2011 ) — The US Food and Drug Administration (FDA) on Friday approved the macrolide antibacterial fidaxomicin (Dificid, Optimer Pharmaceuticals Inc) for the treatment of Clostridium difficile–associated diarrhea (CDAD).

Approval of fidaxomicin tablets was based on 2 trials involving 564 patients with CDAD. In those trials, fidaxomicin was shown to have efficacy and safety similar to those of vancomycin.

The trials also showed that more patients treated with fidaxomicin had a sustained response 3 weeks after treatment ended than patients treated with vancomycin. The most common adverse effects included nausea, vomiting, headache, abdominal pain, and diarrhea.

In April this year, upon reviewing results of the 2 studies, the FDA's Anti-Infective Drugs Advisory Committee unanimously recommended fidaxomicin for the treatment of life-threatening C difficile–associated diarrhea.

"In recent years, many in the infectious disease community have seen an increase in the number of cases of people with a C difficile infection," noted Edward Cox, MD, MPH, director of the Office of Antimicrobial Products in the FDA’s Center for Drug Evaluation and Research, in a news release. "[Fidaxomicin] is an effective new treatment option for patients who develop Clostridium difficile–associated diarrhea."

Fidaxomicin should be taken 2 times a day for 10 days with or without food and should be used to treat only infections that are proven or strongly suspected to be caused by C difficile.

According to the FDA, C difficile is a bacterium that can cause diarrhea and result in serious intestinal conditions, such as colitis and in some cases death. "C. difficile bacteria are found in the stool of an infected person, and others can become infected if they touch items or surfaces contaminated with the bacteria or spores and then touch their mouths," the FDA states.

"Fidaxomicin is the second drug (after vancomycin) approved by the FDA for C difficile-associated diarrhea," said John Bartlett, MD, chief of the Division of Infectious Diseases at Johns Hopkins University School of Medicine in Baltimore, Maryland. "The special advantage of fidaxomicin is that it reduces the frequency of relapses, which is a big problem with [C difficile infection]" Dr. Bartlett told Medscape Medical News.

According to Dr. Bartlett, the biologic basis of fidaxomicin is that it is not absorbed, so all that is put in the mouth goes right to the colon. "It is very active against [C difficile infection] since there are no resistant strains with in vitro testing — and it is unlikely that there ever will be resistance," he said.

Vancomycin has the same properties, but it also has a major effect on fecal flora, causing relapse when the drug is stopped. "Vancomycin both causes and cures C difficile diarrhea and colitis. By contrast, fidaxomicin has much less impact on the fecal flora, so it makes sense that relapses would be less frequent," Dr. Bartlett said.

The 2 drugs are comparable with respect to initial treatment, however, and cost will be an issue, as fidaxomicin is substantially more expensive than vancomycin, which is available as a generic, although the more expensive parvule form is sold in drug stores. "Fidaxomicin should largely replace that product, at least until the vancomycin parvule patent comes off." Dr. Bartlett said.