title: Thiopurine metabolite monitoring in paediatric inflammatory bowel disease.
abstract: BACKGROUND
  Measurement of thiopurine metabolite levels may be useful as a clinical tool to optimize thiopurine treatment of paediatric inflammatory bowel disease (IBD).
  
  
  OBJECTIVE
  The authors evaluated correlations between 6-thioguanine nucleotide (6-TGN) and therapeutic response, metabolite levels and drug toxicity.
  
  
  METHODS
  Fifty-six paediatric IBD patients treated with thiopurines had 326 metabolite level measurements and were retrospectively reviewed. Clinical status and laboratory parameters were compared with metabolite levels.
  
  
  RESULTS
  There was significant correlation between 6-TGN levels and therapeutic response, with higher median 6-TGN levels among patients with therapeutic response than those with non-therapeutic response (194 vs. 146 pmol/8 x 10(8) RBC; P = 0.0004). Patients with 6-TGN levels >235 pmol/8 x 10(8) RBC were more likely to achieve therapeutic response than those below the cut-off (odds ratio, 2.5; 95% CI, 1.5-4.1). Patients who developed leukopenia tended to have higher median 6-TGN levels than those without leukopenia (261 vs. 160 pmol/8 x 10(8) RBC) but the difference was not statistically significant. There was no correlation between 6-methylmercaptopurine levels and hepatotoxicity. Two patients developed acute pancreatitis. Metabolite level measurements were helpful in identifying non-compliance in nine patients.
  
  
  CONCLUSIONS
  Monitoring of thiopurine metabolite levels is useful to guide and optimize dosing, as an adjunct to clinical judgement, blood count and liver biochemistry measurements to minimize the risk of drug toxicity and to confirm non-compliance.
authors.affiliation: Department of Gastroenterology, and Sydney Children's Hospital and School of Women's & Children's Health, University of New South Wales, Sydney, NSW, Australia.
authors.forename: C Y
authors.initials: CY
authors.lastname: Ooi
authors.forename: T D
authors.initials: TD
authors.lastname: Bohane
authors.forename: D
authors.initials: D
authors.lastname: Lee
authors.forename: D
authors.initials: D
authors.lastname: Naidoo
authors.forename: A S
authors.initials: AS
authors.lastname: Day
mesh_terms: D000293:Adolescent; D001379:Azathioprine / Q000378:metabolism / Q000627:therapeutic use*; D056486:Chemical and Drug Induced Liver Injury; D002648:Child; D002675:Child, Preschool; D004342:Drug Hypersensitivity / Q000209:etiology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000378:metabolism / Q000627:therapeutic use*; D007223:Infant; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy* / Q000378:metabolism; D007970:Leukopenia / Q000139:chemically induced; D008297:Male; D015122:Mercaptopurine / Q000378:metabolism / Q000627:therapeutic use*; D010195:Pancreatitis / Q000139:chemically induced; D012189:Retrospective Studies; D013866:Thioguanine / Q000378:metabolism*; D013921:Thrombocytopenia / Q000139:chemically induced; D016312:Treatment Refusal
chemical_list: D007166:Immunosuppressive Agents; D015122:Mercaptopurine; D013866:Thioguanine; D001379:Azathioprine