But vancomycin appears to have an edge in severe disease.
Metronidazole and vancomycin are generally thought to be equivalent for the treatment of Clostridium difficile–associated diarrhea (CDAD), although the evidence for this assumption is fairly limited. Chicago researchers now report results from the first blinded, controlled, head-to-head comparison of the two agents.
Over an 8-year period, 172 hospitalized patients with confirmed CDAD were stratified into those with mild disease and those with severe disease (based on a scale including age, temperature, serum albumin, white blood cell count, presence of pseudomembranous colitis on endoscopy, and ICU care). Both groups were separately randomized to receive either oral vancomycin (125 mg 4 times daily) or oral metronidazole (250 mg 4 times daily) for 10 days.
Overall, the cure rate at 6 days was slightly but significantly higher with vancomycin than with metronidazole (97% vs. 84%). This finding reflected vancomycin’s superiority among patients with severe disease (97% vs. 76%); the two drugs performed equivalently in patients with mild disease. Overall rates of relapse were slightly but not significantly higher in the metronidazole group. Adverse reactions to treatment were rare in both groups.
Comment: Although metronidazole is generally favored as first-line treatment for CDAD for its good performance and low cost, infectious diseases consultants often feel oral vancomycin is still superior, possibly because of its high levels in the gut lumen. This study confirms that assumption. However, it was completed in 2002, before the current epidemic of disease caused by hypervirulent C. difficile strains. We can assume its findings still hold, but they deserve reconfirmation.
Published in Journal Watch General Medicine August 7, 2007
Zar FA et al. A comparison of vancomycin and metronidazole for the treatment of Clostridium difficile-associated diarrhea, stratified by disease severity. Clin Infect Dis 2007 Aug 1; 45:302-7.