Smoking Status and Response to Thiopurines in Steroid-dependent Inflammatory Bowel Disease

Background: The influence of smoking on inflammatory bowel disease (IBD) susceptibility and on its clinical course is well known, but not its impact on drug efficacy. The aim of this study was to evaluate the response to thiopurines in patients with steroid-dependent IBD according to their smoking habits. Methods: The medical records of 163 IBD patients (103 Crohn's disease [CD], 60 ulcerative colitis [UC]) in whom thiopurines were started because of steroid-dependency were reviewed. Therapeutic response was defined by steroid-free clinical remission for at least 6 months after 12 months of starting thiopurines. Clinical data and smoking status at diagnosis, at the time thiopurines were started, and during the follow-up were registered. Results: A therapeutic response was obtained in 72% of CD and 61% of UC patients. Smoking habits did not influence the rate of response to thiopurines, the need for rescue therapies, or the development of penetrating/stricturing complications (CD) or proximal progression (UC). However, CD responders who continued smoking required new courses of steroids more often during follow-up. No influence of smoking was found when these outcomes were analyzed depending on gender or disease location. In the multivariate analysis, smoking status was the only predictive factor of drug tolerance. Conclusions: Active smoking does not influence the response to thiopurines in steroid-dependent IBD, but may decrease the likelihood of drug tolerance.