Oral Metronidazole Equivalent to Vancomycin for C difficile

Daniel M. Keller, PhD

September 23, 2011

September 23, 2011 (Chicago, Illinois) — Oral vancomycin and oral metronidazole appear to be equally effective in treating patients with Clostridium difficile infection, regardless of the severity of infection, lead author Qamar Saleheen, MD, an infectious diseases fellow at the Hines Veterans Administration (VA) Hospital in Illinois, reported during a poster session here at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy.

The rate of recurrence and the complication rate were not statistically different between the 2 drugs, he announced.

Dr. Saleheen noted that the May 2010 guidelines of the Society for Healthcare Epidemiology of America (SHEA) recommend oral metronidazole for mild to moderate infections and oral vancomycin for more severe infections.

The investigators used a retrospective chart review to judge the response to treatment and the relation between the severity of illness and the response to each drug. From January 1, 2009 to March 31, 2010, 147 patients were enrolled in the study. C difficile infection was defined as the presence of diarrhea and a positive stool toxin test result or a finding of pseudomembranous colitis on colonoscopy. Only patients who had been treated solely with oral metronidazole and/or vancomycin were included. Exclusion criteria were HIV infection, no treatment received, no diarrhea, and the use of other drugs for C difficile infection.

According to SHEA criteria, illness was defined as severe if leukocytosis was 15,000 cells/μL or more or serum creatinine level was at least 1.5 times the premorbid level.

Clinicians chose the initial treatment drugs — either oral metronidazole (n = 122) or oral vancomycin (n = 25). Twenty-eight patients in the metronidazole group crossed over to the vancomycin group. No patient initially in the vancomycin group crossed over to the metronidazole group.

Of the 25 patients in the vancomycin group, 14 had severe disease, 3 of which were recurrences of C difficile infection (21%). There were no recurrences among the 11 patients with nonsevere disease (0%).

Among the 59 patients with severe disease in the metronidazole group, there were 16 recurrences (27%); among the 63 patients with nonsevere disease, there were 11 recurrences (17%).

The rate of complications (intensive care unit admission, shock, megacolon, colon perforation, or 30-day mortality) was 21% in the vancomycin group and 22% in the metronidazole group.

The investigators concluded that metronidazole and vancomycin were equivalent, regardless of the severity of illness (P = .14), the rate of disease recurrence (P = .41), or the rate of complications (P = .77). The data indicated that clinicians chose a treatment regimen irrespective of the severity of illness.

The study was limited by its retrospective nature, a relatively small study population, and the fact that only 2 of the patients were women, which was not unexpected, given that the study site was a VA hospital.

Clifford McDonald, MD, chief of the Prevention and Response Branch, Division of Healthcare Quality Promotion, US Centers for Disease Control and Prevention, in Atlanta, Georgia, told Medscape Medical News that for the study population, "it didn't really appear that clinicians were following the [SHEA] guidelines in the first instance. To them, it looked like it didn't make a difference." He noted that this is only one problem of confounding, and a study limitation "that you just can't get beyond" in a retrospective study like this.

He pointed out that findings from randomized controlled studies, on which treatment standards should be based, are more rigorous. "In several of those studies, where...you randomize people into the 2 treatments, that the more severe cases do better with the vancomycin than metronidazole. That's where the [SHEA] recommendation came from." Nonetheless, there is still an issue of how to define the severity of illness, he said, adding that studies have varied on this point.

In practice, Dr. McDonald said another important issue is the high cost of oral vancomycin. "Some hospital pharmacies have gotten around that by using intravenous vancomycin," which is much less expensive, he said.

The study had no commercial funding. Dr. Saleheen and Dr. McDonald have disclosed no relevant financial relationships.

51st Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Abstract K-197. Presented September 17, 2011.

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