Topical Metronidazole for Post-Anal Surgery Pain

Objective metronidazole is a widely used antibiotic against anaerobic micro-organisms. It& #039, s efficacy in reducing post-anal surgery pain was evaluated in this study. Design A randomized, single blind placebo-control study was conducted prospectively using 60 female patients with 4th grade hemorrhoids and low-lying anal fistulae, who were divided into two equal groups, both received topical three times a day applications of ointments (10 % metronidazole versus placebo) for two weeks. Patients were provided with a chart to record their pain at 6hr, 12hr, 4d, 7d, 10d and 14d post-operatively (and the use of injectable non-narcotic analgesic, post-operative complications were also reported). All patients were reviewed 14 days after the surgery. Results Twelve hours post-operatively, significant number of patients in both groups complained of severe pain. Twenty four hours postoperatively, a statistically significant reduction in post-operative pain among metronidazole group was noticed. This pain reduction became more from the 4th post-operative day and on. A statistically-significant reduction in on-defecation pain was noted from the 1st post-operative day among the metronidazole group while more than half of those treated with placebo remained symptomatic even after 2 weeks of surgery. A statistically significant difference in the need for non-narcotic parenteral analgesia was noted between the two studied groups whereby 80 % of metronidazole-treated patients needed single daily injection while about 97 % of the placebo group needed 2-3 injections per day. Foul smell discharge and pruritus were reported much less in the metronidazole-group than in placebo group (P=0.0003 and P=0.0009 respectively). Within the metronidazole-treated group, there was no difference in the reduction of post-operative pain, on-defecation pain and other post-operative complications between patients of hemorroidectomy and fistulectomy. Conclusion Topical 10 % metronidazole is effective in reducing post-operative pain in anal surgeries, reducing on-defecation pain, decreasing analgesic requirements, and minimizing foul smell discharge and pruritus.