Thiopurine effective for long-term use in ulcerative colitis but less so in Crohn’s disease

Thiopurine appears beneficial for long-term treatment of patients with ulcerative colitis (UC) but not for those with Crohn’s disease (CD) especially where there is perianal involvement, a study has found.

The analysis included 4,968 UC patients (median age, 33 years; median time from diagnosis, 10 years) and 6,960 CD patients (median age, 26 years; median time from diagnosis, 12 years) treated with thiopurine monotherapy in real-world settings. Overall, 11,239 patients (94.2 percent) received azathioprine (AZA) and 2,698 (22.6 percent) 6-mercaptopurine (6MP); these included 2,009 patients (16.8 percent) who received both drugs at different time points.

Median duration of thiopurine was 8 years for CD and 9 years for UC, with treatment initiated a median of 2 years after diagnosis for both groups. Adverse events were consistent with those reported previously, with nausea, vomiting, and deranged liver function tests being the most common. More CD patients permanently discontinued treatment due to pancreatitis (2.7 percent vs 1.2 percent; p<0.0001), whereas a greater number of UC patients had treatment-limiting hepatotoxicity (3.2 percent vs 2.1 percent; p=0.0003).

Thiopurine monotherapy was effective throughout the duration of treatment in 52.7 percent of UC patients as compared with only 34.2 percent of those with CD (p<0.0001). Multivariable logistic regression models confirmed that the drug was less effective in CD than UC (odds ratio, 0.47, 95 percent confidence interval, 0.43–0.51; p<0.0001).

Intolerance to treatment was associated with a significantly greater risk of surgery in UC (hazard ratio [HR], 2.44; p<0.0001) and in CD albeit at a lesser magnitude (HR, 1.23; p=0.0015).