title: Thioguanine: a potential alternate thiopurine for IBD patients allergic to 6-mercaptopurine or azathioprine.
abstract: OBJECTIVE
  Approximately 10% of inflammatory bowel disease (IBD) patients receiving 6-mercaptopurine (6-MP) or azathioprine (AZA) develop drug hypersensitivity reactions necessitating early discontinuation of these traditional thiopurines. These allergic reactions typically reoccur upon rechallenge. Our recently published pilot study suggested that thioguanine (6-TG), a closely related thiopurine, was efficacious and well tolerated in IBD patients resistant to 6-MP/AZA. The aim of this study was to determine if hypersensitivity reactions to 6-MP/AZA reoccur with 6-TG therapy.
  
  
  METHODS
  IBD patients allergic to 6-MP and/or AZA were treated with 6-TG as an alternate thiopurine. Hypersensitivity reactions to 6-MP/AZA must have been documented within 6 wk of 6-MP/AZA initiation.
  
  
  RESULTS
  6-TG was initiated in 21 IBD patients at a median (range) dose of 20 (10-40) mg/day. 6-TG hypersensitivity reaction occurred in only four of 21 (19%) patients after a median time interval of 9 days. Pancreatitis did not reoccur with 6-TG. Eighty-two percent of 6-TG tolerant patients were assessed as improved at last follow-up.
  
  
  CONCLUSIONS
  These results suggest that 6-TG may be considered as a possible alternate thiopurine in patients allergic to traditional 6-MP/AZA. Despite these favorable results, candidates for 6-TG should be selected with caution, and its use should be reserved for IBD patients well informed about potential toxicities.
authors.affiliation: Department of Medicine, Division of Gastroenterology, Cedars-Sinai Medical Center, UCLA, Los Angeles, California 90048, USA.
authors.forename: Marla C
authors.initials: MC
authors.lastname: Dubinsky
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Feldman
authors.forename: Maria T
authors.initials: MT
authors.lastname: Abreu
authors.forename: Stephan R
authors.initials: SR
authors.lastname: Targan
authors.forename: Eric A
authors.initials: EA
authors.lastname: Vasiliauskas
mesh_terms: D000328:Adult; D001379:Azathioprine / Q000009:adverse effects*; D004342:Drug Hypersensitivity / Q000209:etiology*; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects*; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy*; D007413:Intestinal Mucosa; D008297:Male; D015122:Mercaptopurine / Q000009:adverse effects*; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D012449:Safety; D013866:Thioguanine / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D007166:Immunosuppressive Agents; D015122:Mercaptopurine; D013866:Thioguanine; D001379:Azathioprine