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Aliment Pharmacol Ther. 2003 Dec;18(11-12):1113-20.

Antibiotics and azathioprine for the treatment of perianal fistulas in Crohn's disease.

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Department of Internal Medicine IV, Division of Gastroenterology and Hepatology, Institute of Tumour Biology, University Hospital, Vienna, Austria.



Antibiotics and thiopurines have been employed in the management of fistulizing Crohn's disease, although evidence of their efficacy is rare.


To evaluate, in a prospective, open-label study, the influence of antibiotics and azathioprine on the clinical outcome of perianal fistulas in patients with Crohn's disease.


Fifty-two patients entered the study, starting with an 8-week regimen of ciprofloxacin (500-1000 mg/day) and/or metronidazole (1000-1500 mg/day). Seventeen patients had already received daily azathioprine (2-2.5 mg/kg) at enrollment, whereas in 14 patients azathioprine was initiated after 8 weeks of antibiotic treatment. Outcome was evaluated by Fistula Drainage Assessment and the Perianal Disease Activity Index at weeks 8 and 20.


Overall, 26 patients (50%) responded to antibiotic treatment, with complete healing in 25% of patients at week 8. The Perianal Disease Activity Index decreased significantly from 8.4 +/- 2.9 to 6.0 +/- 4.0 (P < 0.0001). At week 20, the outcome was assessed in 49 patients (94%), 29 of whom (59%) had received azathioprine. Response was noted in 17 of the 49 patients (35%), with complete healing in nine patients (18%). Patients who received azathioprine were more likely to achieve a response (48%) than those without immunosuppression (15%) (P = 0.03). The Perianal Disease Activity Index was closely associated with treatment response and perianal disease activity.


Antibiotics are useful to induce a short-term response in perianal Crohn's disease, and may provide a bridging strategy to azathioprine, which seems to be essential for the maintenance of fistula improvement.

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