Prophylactic metronidazole in appendectomy: a double-blind controlled trial.

Ninety-eight patients with suspected nonperforated acute appendicitis have to date been entered into a continuing, prospective, blinded randomized trial to determine the role of prophylactic metronidazole in postoperative wound infection. Twenty-six patients were excluded for the following reasons: diagnosis other than acute appendicitis (16), perforation of the appendix (8), administration of other antibiotics (1), and refusal to enter study (1). Seventy-two patients, 47 men and 25 women, with a mean age of 27.5 years (range 15 to 60 years), underwent appendectomy and were studied. Thirty patients received 1 gm intravenous metronidazole preoperatively and five intravenous doses of 500 mg metronidazole postoperatively. Forty-two patients received placebo only. Cultures of the appendiceal stump grew aerobic cultures in 45 (62%) and anaerobic organisms in 29 (40%): Escherichia coli and Bacteroides fragilis, respectively. Six of the 72 patients (8.2%) developed postoperative wound infections: four of 42 (9.5%) who received placebo and two of 30 (6.6%) who received metronidazole (P = 0.54 by Fisher exact test). No toxicity from metronidazole was observed. The postoperative wound infection rate is insufficient to demonstrate the efficacy of metronidazole for prophylaxis in nonperforated acute appendicitis, although there appears to be a tendency of to assume its efficacy in this regard.