title: Measurement of thiopurine methyltransferase activity and azathioprine metabolites in patients with inflammatory bowel disease.
abstract: BACKGROUND
  Measurement of 6-thioguanine nucleotide concentrations may be useful for optimising treatment with azathioprine and 6-mercaptopurine.
  
  
  METHODS
  We conducted a study of 170 patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine to determine the relationship between 6-thioguanine nucleotide concentrations and both disease activity, as measured by the inflammatory bowel disease questionnaire (active disease < 170, remission > or = 170) and leucopenia. Blood was submitted for whole blood 6-thioguanine nucleotide concentration and leucocyte count.
  
  
  RESULTS
  Mean (SD) inflammatory bowel disease questionnaire score was 176 (32). There was no correlation between inflammatory bowel disease questionnaire scores and 6-thioguanine nucleotide concentrations (r(s) = -0.09, p = 0.24). Median 6-thioguanine nucleotide concentrations in 56 patients with active disease and 114 patients in remission were similar (139 v 131 pmol/8 x 10(8) red blood cells; p = 0.26). There was no correlation between 6-thioguanine nucleotide concentrations and leucocyte counts.
  
  
  CONCLUSIONS
  In patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine, 6-thioguanine nucleotide concentrations did not correlate with disease activity, as measured by the inflammatory bowel disease questionnaire, or leucocyte count. These findings are discrepant with most previous studies, possibly due to selection of responding patients who tolerated the medications. A prospective, randomised, dose optimisation trial using 6-thioguanine nucleotide concentrations is warranted.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA.
authors.forename: P W
authors.initials: PW
authors.lastname: Lowry
authors.forename: C L
authors.initials: CL
authors.lastname: Franklin
authors.forename: A L
authors.initials: AL
authors.lastname: Weaver
authors.forename: M G
authors.initials: MG
authors.lastname: Pike
authors.forename: D C
authors.initials: DC
authors.lastname: Mays
authors.forename: W J
authors.initials: WJ
authors.lastname: Tremaine
authors.forename: J J
authors.initials: JJ
authors.lastname: Lipsky
authors.forename: W J
authors.initials: WJ
authors.lastname: Sandborn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001379:Azathioprine / Q000097:blood* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood* / Q000627:therapeutic use; D015212:Inflammatory Bowel Diseases / Q000097:blood / Q000188:drug therapy*; D007970:Leukopenia / Q000139:chemically induced; D008297:Male; D015122:Mercaptopurine / Q000097:blood / Q000627:therapeutic use; D008780:Methyltransferases / Q000097:blood*; D008875:Middle Aged; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric
chemical_list: D007166:Immunosuppressive Agents; D015122:Mercaptopurine; D008780:Methyltransferases; C022745:thiopurine methyltransferase; D001379:Azathioprine