ANTIMICROBIAL THERAPY OF INFLAMMATORY BOWEL-DISEASE - IMPLICATIONS FOR PATHOGENESIS AND MANAGEMENT

Universally accepted indications for the use of antibiotics in bowel d isease include treatment of septic complications such as abscesses, ba cterial overgrowth and toxic megacolon. The role of antibiotics as pri mary or secondary therapeutic agents for active intestinal inflammatio n is more controversial. Tetracycline, trimethoprim-sulphamethoxazole and ampicillin are used empirically by some experienced clinicians as alternatives to corticosteroids in patients with Crohn's disease but h ave not been subjected to well designed clinical trials. Only anecdota l reports suggest a benefit of broad spectrum antibiotics and bowel de contamination in patients with active ulcerative colitis. However, met ronidazole (10 mg/kg) is equal to sulphasalazine and superior to place bo in well designed studies of patients with active Crohn's disease, w ith a particular benefit to those patients with colonic involvement. H igh dose metronidazole (20 mg/kg) is widely used for perianal complica tions of Crohn's disease, although its utility has never been document ed by controlled trials. Reduction of luminal bacterial concentrations by intestinal lavage and nonabsorbable antibiotics induces remissions of Crohn's disease in uncontrolled trials but have not been used clin ically. Long term use of antibiotics is tempered by the risk of compli cations, notably Clostridium difficile toxin-induced colitis with broa d spectrum antibiotics and peripheral neuropathy after high dose metro nidazole. The author advocates use of metronidazole 250 mg tid or qid (10 mg/kg) in patients with Crohn's colitis or ileocolitis who do not respond to sulphasalazine or 5-ASA, and treatment of perianal complica tions of Crohn's disease with metronidazole 500 mg tid (20 mg/kg), wit h immediate cessation of the drug if peripheral neuropathy occurs.