title: Mercaptopurine metabolite results in clinical gastroenterology practice.
abstract: BACKGROUND
  Azathioprine (AZA) and its active metabolite mercaptopurine (MP) are frequently used in the management of inflammatory bowel disease. Measurement of the AZA/MP metabolites, thioguanine (TG) and methylmercaptopurine (MMP), has been suggested as a means to optimize therapy with AZA/MP in inflammatory bowel disease.
  
  
  OBJECTIVE
  To evaluate the results of initial AZA/MP metabolite panels sent by gastroenterologists during the first year of its widespread availability.
  
  
  METHODS
  Initial AZA/MP metabolite panels sent by gastroenterologists to a single laboratory were reviewed and the metabolite panels were interpreted.
  
  
  RESULTS
  Initial metabolite levels were reviewed for 9187 patients. Noncompliance was detected in 263 patients (3%) and under-dosing in 4260 patients (46%). 534 patients (6%) had levels that were consistent with preferential metabolism via the TPMT pathway. The therapeutic goal was achieved in 2444 patients (27%) and an additional 552 patients (6%) had appropriate TG levels but potential hepatotoxicity. 936 patients (10%) had potential TPMT deficiency, and 58 patients (1%) had potential TPMT absence and were at risk for leukopenia. 140 patients (2%) had too high a dose.
  
  
  CONCLUSIONS
  Measurement of AZA/MP metabolites can be used by practising gastroenterologists to identify potential reasons for nonresponse to AZA or MP, and to identify patients at risk for certain drug-related toxicities.
authors.affiliation: Section of Gastroenterology, Wake Forest University Baptist Medical Center, Medical Center Boulevard, Winston-Salem, NC 27157, USA. rbloomfe@wfubmc.edu
authors.forename: R S
authors.initials: RS
authors.lastname: Bloomfeld
authors.forename: J E
authors.initials: JE
authors.lastname: Onken
mesh_terms: D001379:Azathioprine / Q000378:metabolism*; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy* / Q000378:metabolism; D015122:Mercaptopurine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000627:therapeutic use*; D010349:Patient Compliance; D012307:Risk Factors; D013866:Thioguanine / Q000378:metabolism*
chemical_list: C010240:6-methylthiopurine; D015122:Mercaptopurine; D013866:Thioguanine; D001379:Azathioprine