The researchers investigated the efficacy of azathioprine for the treatment of inflammatory bowel disease (IBD) over a period of 30 years.
They reported their results in the April issue of Gut.
The notes of patients attending the Oxford IBD clinic in England, from 1968 to 1999, were reviewed.
Remission was defined as no need for oral steroids for at least 3 months, and relapse was defined as active disease requiring steroids.
A total of 622 of 2205 patients were treated with azathioprine (272 Crohn's disease, 346 ulcerative colitis, and 4 indeterminate colitis).
Mean duration of the initial course of treatment was 634 days.
The overall remission rates were 45% for Crohn's disease and 58% for ulcerative colitis. For the 424 patients who received more than 6 months of treatment, remission rates were 64% and 87%, respectively.
The investigators found that the factors favoring remission were ulcerative colitis, lower white blood cell (WBC) or neutrophil counts, higher mean cell volume, and older age.
For Crohn's disease, colonic disease favored remission.
|IBD patients in remission with azathioprine:|
1 year: 95%
3 years: 69%
5 years: 55%
Factors that were not significant were age, sex, lymphocyte count, and dose (mg/kg).
The proportion of patients remaining in remission at 1, 3, and 5 years was 95%, 69%, and 55%, respectively.
The chance of remaining in remission was found to be higher if WBC was less than 5x109 and in male patients (Crohn's disease only).
There was no difference in relapse rates between Crohn's disease and ulcerative colitis.
After stopping azathioprine, the proportion of patients remaining in remission at 1, 3, and 5 years was 63%, 44%, and 35% (222 patients).
The authors found that duration of azathioprine treatment did not affect the relapse rate after stopping treatment.
Author A. G. Fraser, of the University of Auckland, New Zealand, concluded on behalf of the group, "Azathioprine is effective treatment for ulcerative colitis and Crohn's disease.
"The efficacy of azathioprine is reasonably well sustained over 5 years."