title: Clinical Value of Mercaptopurine After Failing Azathioprine Therapy in Patients With Inflammatory Bowel Disease.
abstract: Thiopurines have been widely accepted as immunosuppressive therapy in inflammatory bowel disease. However, many patients have to discontinue thiopurines due to intolerance or ineffectiveness. A therapeutically beneficial effect of switching from azathioprine (AZA) to mercaptopurine (MP) after developing adverse events (AEs) has been reported. The authors assessed the clinical value of MP therapy after AZA discontinuation due to intolerance and, secondary, due to ineffectiveness.
  
  
  
  In this retrospective single-center study, the authors analyzed data from patients in whom AZA therapy had failed and who were subsequently treated with MP.
  
  
  
  Thirty-eight patients initiated MP therapy after intolerance to AZA. Intolerance reoccurred in 22 (58%) patients and the remaining 16 (42%) tolerated MP. In 18 out of 48 patients (38%), the AEs that led to discontinuation of MP were similar to those of AZA. A longer duration of prior AZA use was more common in patients who were subsequently tolerant for MP (5.3 versus 1.2 months; P = 0.04). Twenty-two patients discontinued AZA due to ineffectiveness. Eight (36%) patients had clinical benefit from a switch to MP. Six out of these 8 (75%) patients used allopurinol alongside MP, due to ineffectiveness based on a skewed thiopurine metabolism. Patients were more likely to have clinical benefit if the interval between both thiopurines was longer (4.4 versus 0.01 months; P < 0.05).
  
  
  
  The authors showed that a noteworthy number of patients benefitted therapeutically from a switch from AZA to MP when failing due to intolerance or ineffectiveness; however, the percentage was lower than previously reported in literature.
authors.affiliation: *Department of Gastroenterology and Hepatology, VU University Medical Center, Amsterdam; and †Department of Gastroenterology, Geriatrics, Internal and Intensive Care Medicine (Co-MIK), Zuyderland Medical Center, Heerlen-Sittard-Geleen, the Netherlands.
authors.forename: Berrie
authors.initials: B
authors.lastname: Meijer
authors.forename: Margien L
authors.initials: ML
authors.lastname: Seinen
authors.forename: Niek N W
authors.initials: NN
authors.lastname: Leijte
authors.forename: Chris J J
authors.initials: CJ
authors.lastname: Mulder
authors.forename: Adriaan A
authors.initials: AA
authors.lastname: van Bodegraven
authors.forename: Nanne K H
authors.initials: NK
authors.lastname: de Boer
mesh_terms: D000293:Adolescent; D000328:Adult; D000493:Allopurinol / Q000627:therapeutic use; D001379:Azathioprine / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy*; D008297:Male; D015122:Mercaptopurine / Q000627:therapeutic use*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D007166:Immunosuppressive Agents; D000493:Allopurinol; D015122:Mercaptopurine; D001379:Azathioprine