Prospective Randomised Trial of Metronidazole Versus Vancomycin for Clostridium-difficile-associated Diarrhoea and Colitis

101 patients with Clostridium-difficile-associated diarrhoea or colitis were prospectively randomised to 10-day oral courses of metronidazole, 250 mg four times a day, or vancomycin, 500 mg four times a day. 7 did not complete the protocol and were dropped from analysis. Pseudomembranous colitis (PMC) was diagnosed after endoscopy in 33 patients. Of the remaining patients without PMC, 38 had both C difficile culture and cytotoxin and 23 had only culture evidence of C difficile. 52 evaluable patients received vancomycin and 42 received metronidazole. There were two treatment failures with metronidazole and none with vancomycin (p = 0.20); and two relapses with metronidazole versus six with vancomycin (p = 0.17). Treatment in 1 patient in each group was discontinued because of drug intolerance. Response and relapse rates of the 33 patients with PMC were no different from those of the remaining patients. Pharmacy cost for the dosage used was $387.48 to $520.00 for vancomycin and $11.84 for metronidazole. Metronidazole and vancomycin have equivalent efficacy and relapse rates and are tolerated to a similar extent by patients with C-difficile-related diarrhoea and colitis, but metronidazole is considerably more economical.