ObjectiveMercaptopurine (MP) and pro-drug azathioprine are ‘first-line’ oral therapies for maintaining remission in IBD. It is believed that their pharmacodynamic action is due to a slow cumulative decrease in activated lymphocytes homing to inflamed gut. We examined the role of host metabolism, lymphocytes and microbiome for the amelioration of colitis by the related thioguanine (TG).DesignC57Bl/6 mice with or without specific genes altered to elucidate mechanisms responsible for TG's actions were treated daily with oral or intrarectal TG, MP or water. Disease activity was scored daily. At sacrifice, colonic histology, cytokine message, caecal luminal and mucosal microbiomes were analysed.ResultsOral and intrarectal TG but not MP rapidly ameliorated spontaneous chronic colitis in Winnie mice (point mutation in Muc2 secretory mucin). TG ameliorated dextran sodium sulfate-induced chronic colitis in wild-type (WT) mice and in mice lacking T and B lymphocytes. Remarkably, colitis improved without immunosuppressive effects in the absence of host hypoxanthine (guanine) phosphoribosyltransferase (Hprt)-mediated conversion of TG to active drug, the thioguanine nucleotides (TGN). Colonic bacteria converted TG and less so MP to TGN, consistent with intestinal bacterial conversion of TG to so reduce inflammation in the mice lacking host Hprt. TG rapidly induced autophagic flux in epithelial, macrophage and WT but not Hprt−/− fibroblast cell lines and augmented epithelial intracellular bacterial killing.ConclusionsTreatment by TG is not necessarily dependent on the adaptive immune system. TG is a more efficacious treatment than MP in Winnie spontaneous colitis. Rapid local bacterial conversion of TG correlated with decreased intestinal inflammation and immune activation.

The proven therapeutic efficacy of methadone in cancer pain is hindered by a challenging pharmacokinetic-pharmacodynamic profile, considerable interpatient variation, and increasing concern about the complexities of dosing. The objective of this study was to assess the evidence for the use of methadone in cancer pain management. The authors conducted a systematic literature search for randomized controlled trials (RCTs) published post the 2007 Cochrane review of methadone in cancer pain. Trial quality was assessed using the Oxford Quality Scoring System and Cochrane Handbook for Systematic Reviews of Interventions. Of the 152 abstracts found, 4 were RCTs (272 participants). Two RCTs compared the efficacy and safety of methadone with placebo or active control and two investigated rotation to methadone from other opioids. The studies used different routes of administration, dosing, initiation, and titration of methadone and distinct pain scoring tools and did not address the issues raised by the Cochrane review. Methadone has an important role in the management of cancer pain, with many advantages including low cost, high oral bioavailability, rapid onset of action, once-daily dosing, and postulated benefits in difficult pain control scenarios. However, due to limited research in this area, methadone dosing remains a challenge, with vigilant dose initiation, adjustment, and monitoring required. There is a need for further studies using standardized methodology to evaluate the optimal dosing strategy of methadone, the effect on different types of pain, and the role of pharmacokinetics and pharmacogenomics in clinical outcomes.