Oral metronidazole as antibiotic prophylaxis for patients with nonperforated appendicitis Original paper

What was studied?

This randomized controlled trial investigated the effectiveness of oral metronidazole as a prophylactic antibiotic compared to intravenous metronidazole in patients undergoing open appendectomy for nonperforated appendicitis. The researchers aimed to determine whether a single preoperative oral dose could provide the same protection against surgical wound infections as intravenous administration. The trial was conducted across two teaching hospitals affiliated with Mashhad University of Medical Sciences in Iran between June 2007 and July 2009.

Who was studied?

The study enrolled 204 pediatric and adult patients, aged between 7 and 57 years, who underwent open appendectomy and were confirmed intraoperatively to have nonperforated appendicitis. Researchers excluded patients with diabetes, those on steroids, pregnant women, individuals under 5 or over 60 years of age, and those with known metronidazole allergies or prior antibiotic use. The researchers randomized the participants into two groups: they administered oral metronidazole to 102 patients 2–3 hours before surgery and intravenous metronidazole to another 102 patients 30 minutes before the procedure.

What were the most important findings?

The findings showed no statistically significant difference in wound infection rates between the oral and intravenous groups—6% in the oral group and 4% in the intravenous group (P = 0.861). Likewise, the postoperative hospital stay was statistically similar between groups: 2.3 days for oral and 2.7 days for intravenous. These results suggest that oral metronidazole is just as effective as its intravenous counterpart in preventing postoperative infections for nonperforated appendicitis.

While the study did not directly evaluate microbiome profiles, its relevance to microbiome-targeted therapy is notable. Because metronidazole targets anaerobic bacteria, including Bacteroides and Clostridium species, its use in prophylaxis may temporarily disrupt microbial balance. Clinicians benefit from using oral metronidazole because it avoids intravenous administration, retains high bioavailability, and provides a more accessible and microbiome-conscious option when briefly prescribing a narrow-spectrum anaerobic antibiotic.

What are the implications of this study?

This study provides compelling evidence for clinicians that oral metronidazole can serve as an effective, cost-efficient, and microbiome-considerate alternative to intravenous antibiotic prophylaxis in nonperforated appendectomy cases. In resource-limited settings or outpatient surgical centers, where intravenous access may delay care or increase costs, this finding allows for streamlined surgical workflows and reduced healthcare expenses without compromising patient outcomes. Moreover, using a single oral dose limits prolonged exposure, which may help preserve anaerobic microbial diversity better than extended-spectrum regimens. While the study does not offer direct microbiome sequencing data, its antibiotic stewardship implications are significant.