Tioguanine in patients with Crohn's disease intolerant or resistant to azathioprine/mercaptopurine

Background: Tioguanine (TG) is an antimetabolite which may be regarded as an alternative to azathioprine (AZA)/mercaptopurine (MP) in patients with inflammatory bowel diseases. Aims: To evaluate the tolerance and efficacy of TG in patients with Crohn's disease, intolerant or resistant to AZA/MP. Methods: An open prospective study was made on Crohn's disease patients treated with TG. Intolerance to AZA/MP was defined as a reaction occurring within 1 month after introduction of AZA/MP, including pancreatitis, abdominal pain, fever, arthralgia, myalgia, cutaneous rash, fatigue, alopecia, hepatitis and digestive intolerance. Resistance to AZA/MP was defined as the persistence of activity after at least 3 months of AZA/MP therapy. Results: Forty-nine Crohn's disease patients (36 women, 13 men; intolerance: n = 39; resistance: n = 10) were treated with TG (20 mg/day). Clinical pancreatitis did not recur under TG. Five patients (10%) had to stop TG due to intolerant reactions observed 13-21 days after TG was started. No haematological side-effects were observed under TG. The probability of clinical remission without corticosteroids or infliximab at 6 and 12 months was 46% and 79%, respectively, in the 40 patients with active disease at baseline. The probability of clinical relapse during maintenance TG therapy at 6 and 12 months was 29% and 53%, respectively, in the 28 patients in remission at baseline or who had achieved remission on TG. Conclusions: TG is a possible alternative treatment in Crohn's disease patients, intolerant (especially for pancreatitis) or resistant to AZA/MP.