The Food and Drug Administration on May 27 approved the orally administered macrolide antibiotic fidaxomicin for the treatment of Clostridium difficile–associated diarrhea.
In two phase III studies of patients with mild to severe Clostridium difficile–associated diarrhea (CDAD), the clinical cure rates at the end of 10 days of treatment were similar among those treated with fidaxomicin (88%) and among those treated with oral vancomycin (86%-87%). The clinical cure rate was defined as having three or fewer unformed bowel movements for 2 consecutive days or a marked reduction in the number of unformed bowel movements at the end of treatment, plus no further treatment required within 2 days of stopping medication.
More patients treated with fidaxomicin had a lower recurrence rate after treatment ended, compared with those treated with vancomycin, according to the FDA.
Previously, vancomycin was the only other drug treatment approved specifically for treating C. difficile; oral metronidazole is used off label for this indication.
Fidaxomicin – which is taken twice a day for 10 days – has a narrow spectrum of activity, with bactericidal activity against C. difficile, and is poorly absorbed and locally active in the gastrointestinal tract, according to its manufacturer, Optimer Pharmaceuticals Inc. The company will market the drug as Dificid.
"To maintain the effectiveness of Dificid, and to reduce the development of drug-resistant bacteria, the drug should be used only to treat infections that are proven or strongly suspected to be caused by C. difficile," the FDA statement said.
The most common side effects reported with fidaxomicin included nausea, vomiting, headache, abdominal pain, and diarrhea, according to the FDA statement.
At a meeting in April, an FDA advisory panel unanimously agreed that the trials indicated that fidaxomicin was a safe and effective treatment for CDAD. The panel recommended that leukopenia, neutropenia, and GI bleeding in patients treated with the antibiotic should be followed after approval, because the rates of these adverse events were slightly higher among fidaxomicin-treated patients in the studies.
At the meeting, company officials said the company was developing an oral suspension formulation and was planning pediatric studies of the drug.