title: Safety of azathioprine and 6-mercaptopurine in patients with inflammatory bowel disease naïve to thiopurine treatment .
abstract: OBJECTIVE
  To determine if 6-mercaptopurine (MP) is better tolerated than azathioprine (AZA) as the initial thiopurine treatment in patients suffering from inflammatory bowel disease (IBD). Switching patients with IBD from AZA to MP is advocated in patients intolerant to AZA. However, no study has determined if MP is more suited than AZA as a first-line treatment for patients who are naïve to thiopurine treatment.
  
  
  METHODS
  The tolerance of AZA and MP treatments in clinical practice was retrospectively evaluated from start to 12 months after initiating treatment in 113 patients with IBD who were all naïve to thiopurines (82 patients treated with AZA and 31 patients with MP).
  
  
  RESULTS
  65% of the patients treated with AZA and 61% of the patients treated with MP tolerated their treatment during 12 months (i.e., no group difference, p = 0.742). No difference in reported side effects between the two treatments was observed. The mean equivalent initial dose (0.92 vs. 0.61 mg/kg; p < 0.001) and the mean equivalent dose at 12 months (1.98 vs. 1.65 mg/kg; p = 0.014) was significantly higher in the MP group vs. the AZA group. The proportion of patients with ΔMCV ≥ 7 at 12 months was numerically higher in the MP group than in the AZA group (53% vs. 31%; p = 0.090).
  
  
  CONCLUSIONS
  In this retrospective observational study, no differences in tolerance or adherence between AZA and MP were observed in patients naïve to thiopurines. However, MP treatment was at a higher equivalent thiopurine dose than AZA treatment, which tended to be associated with better treatment response. .
authors.forename: Ram
authors.initials: R
authors.lastname: Alaish
authors.forename: David
authors.initials: D
authors.lastname: Lundgren
authors.forename: Ole B
authors.initials: OB
authors.lastname: Suhr
authors.forename: Mårten
authors.initials: M
authors.lastname: Werner
authors.forename: Pontus
authors.initials: P
authors.lastname: Karling
mesh_terms: D000328:Adult; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage* / Q000009:adverse effects; D001379:Azathioprine / Q000008:administration & dosage* / Q000009:adverse effects; D005260:Female; D005765:Gastrointestinal Agents / Q000008:administration & dosage* / Q000009:adverse effects; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000175:diagnosis / Q000188:drug therapy*; D008297:Male; D015122:Mercaptopurine / Q000008:administration & dosage* / Q000009:adverse effects; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000893:Anti-Inflammatory Agents; D005765:Gastrointestinal Agents; D015122:Mercaptopurine; D001379:Azathioprine