Background: Thioguanine (TG) is a treatment for inflammatory bowel disease, but association with nodular regenerative hyperplasia has restricted its use. We conjectured that splitting a therapeutic daily dose of TG would be efficacious and should avoid liver toxicity.
Methods: We report on 62 patients with severe inflammatory bowel disease not responding to prednisolone, conventional thiopurines, biologics, or calcineurin inhibitors. Patients were prescribed oral split-daily TG to avoid individual doses >0.3 mg/kg. Data on concomitant medication, clinical efficacy measured by Harvey-Bradshaw Index for Crohn's, or Simple Clinical Colitis Score for ulcerative/indeterminate colitis (UC), and some paired endoscopies were available. Safety was followed clinically and with bloods at 2 centers. All patients at the U.K. center had a liver biopsy or magnetic resonance imaging after 6 months. Twenty-one patients had serial ultrasounds at the Australian center.
Results: At 6 months, 19/21 of patients with Crohn's disease and 27/38 with ulcerative colitis had improved clinical activity. At study end, 53% of patients maintained improved clinical activity of steroids. Median duration of TG was 8 (0.3-45) months, median dose was 0.6 (0.3-1) mg/kg per day. Previous thiopurine-related adverse reactions were not encountered. Twenty-nine patients withdrew because of loss to follow-up, medical adverse events, or surgery. Possible early nodular regenerative hyperplasia was found on liver biopsy in 1 patient who was heterozygote deficient for thiopurine methyltransferase; the TG dose was lowered. TG was discontinued in a patient with nodular regenerative hyperplasia and concomitant antiphospholipid syndrome. There was 1 successful term pregnancy; cord blood and breast milk TG were low.
Conclusions: Split-dose TG seemed well tolerated and efficacious in this retrospective study of patients with difficult inflammatory bowel disease.