title: Role of thiopurine metabolite testing and thiopurine methyltransferase determination in pediatric IBD.
abstract: Thiopurines have been used in inflammatory bowel disease (IBD) for >30 years, and measurements of both thiopurine methyltransferase (TPMT) and thiopurine (TP) metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP), have been readily available. The North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) Committee on Inflammatory Bowel Disease thought it appropriate to review the present indications for use of TPMT and TP metabolite testing. Substantial evidence demonstrates that TP therapy is useful for both Crohn disease and ulcerative colitis. Review of the existing data yielded the following recommendations. TPMT testing is recommended before initiation of TPs to identify individuals who are homozygote recessive or have extremely low TPMT activity, with the latter having more reliability than the former. Individuals who are homozygous recessive or have extremely low TPMT activity should avoid the use of TPs because of concerns for significant leukopenia. TMPT testing does not predict all cases of leukopenia and has no value to predict hypersensitivity adverse effects such as pancreatitis. Any potential value to reduce the risk of malignancy has not been studied. All individuals taking TPs should have routine monitoring with complete blood cell count and white blood cell count differential to evaluate for leukopenia regardless of TPMT testing results. Metabolite testing can be used to determine adherence with TP therapy. Metabolite testing can be used to guide dose increases or modifications in patients with active disease. Consideration would include either increasing the dose, changing therapy or for those with elevated transaminases or an elevated 6-MMP, using adjunctive allopurinol to help raise 6-thioguanine metabolites and suppress formation of 6-MMP. Routine and repetitive metabolite testing has little or no role in patients who are doing well and taking an acceptable dose of a TP.
authors.affiliation: Mount Sinai School of Medicine, New York, NY 10029, USA. keith.benkov@mssm.edu
authors.forename: Keith
authors.initials: K
authors.lastname: Benkov
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.forename: Ashish
authors.initials: A
authors.lastname: Patel
authors.forename: Riad
authors.initials: R
authors.lastname: Rahhal
authors.forename: Gary
authors.initials: G
authors.lastname: Russell
authors.forename: Jonathan
authors.initials: J
authors.lastname: Teitelbaum
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001711:Biotransformation; D003093:Colitis, Ulcerative / Q000097:blood / Q000188:drug therapy* / Q000378:metabolism; D032921:Consensus; D003424:Crohn Disease / Q000097:blood / Q000188:drug therapy* / Q000378:metabolism; D004347:Drug Interactions; D016903:Drug Monitoring; D019317:Evidence-Based Medicine; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000097:blood / Q000188:drug therapy / Q000378:metabolism; D008780:Methyltransferases / Q000097:blood / Q000378:metabolism*; D017410:Practice Guidelines as Topic; D011687:Purines / Q000009:adverse effects / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D012958:Societies, Scientific; D013438:Sulfhydryl Compounds / Q000009:adverse effects / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D013872:Thionucleosides / Q000009:adverse effects / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D011687:Purines; D013438:Sulfhydryl Compounds; D013872:Thionucleosides; D008780:Methyltransferases; C022745:thiopurine methyltransferase