Metronidazole is an effective method of analgesia following haemorrhoidectomy: a systematic review and meta-analysis

Background: Haemorrhoids are one of the most frequently encountered benign anorectal conditions that negatively impact patients’ quality of life. Excisional haemorrhoidectomy (closed or open) is a surgical procedure reserved for the treatment of third- and fourth-degree haemorrhoids, with considerable post-procedure pain reported. The aim of this study was to clarify the association between post operative metronidazole use (both oral and topical) and post-haemorrhoidectomy pain scores through systematic review and meta-analysis of randomised controlled trials (RCTs). Methods: This study was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Prospective registration was performed on PROSPERO (CRD42024580928). A systematic review was performed for RCTs reporting post-haemorrhoidectomy pain scores between patients who received metronidazole and patients who received placebo. Meta-analysis was performed using RevMan version 5.4. Results: Seventeen RCTs including 1297 participants were eligible for inclusion. Metronidazole administration was associated with significantly lower post-operative visual analogue scores (VAS) on day 1 (−1.18, p < 0.00001), day 2 (−1.15, p = 0.003), day 3 (−0.86, p < 0.00001), and day 7 post-operatively with a mean pain score difference of −1.72 (95% CI −2.27 to −1.18) (p < 0.00001). A significant difference in pain scores was seen on day 3 favouring topical metronidazole in comparison to the oral route (1.38, 95% CI [0.44, 2.32], p = 0.004). Conclusion: This review synthesises the best available evidence to support the use of metronidazole to reduce pain after excisional haemorrhoidectomy. While both oral and topical forms appear to be beneficial, topical administration appears to have a more effective analgesic effect from post-operative day 3.