Metronidazole in Crohn's disease and ulcerative colitis

• antibacterials, such as metronidazole and ciprofloxacin, may be prescribed in the treatment of fistulating Crohn's disease to treat accompanying abscesses or in perianal Crohn's disease or sepsis (1)
• antibiotics, including metronidazole, are indicated in
  • the treatment of symptoms attributable bacterial overgrowth
  • septic complications
  • perineal disease
• significant side-effects of metronidazole include peripheral neuropathy if used long term (over three months), a bad taste in the mouth and a disulfiram-like interaction with alcohol
  

NICE suggest:

• to maintain remission in people with ileocolonic Crohn's disease who have had complete macroscopic resection within the last 3 months, consider azathioprine in combination with up to 3 months' postoperative metronidazole

The routine use of long term antibiotics in the absence of suspected sepsis is not supported by evidence. (2)

Reference

1. NICE. Crohn’s disease: management. NICE guideline NG129. Published May 2019
2. Townsend CM, Parker CE, MacDonald JK, et al. Antibiotics for induction and maintenance of remission in Crohn's disease. Cochrane Database Syst Rev. 2019 Feb 7;(2):CD012730.