Screening for variants in TPMT did not reduce the proportions of patients with hematologic ADRs during thiopurine treatment for IBD. However, there was a 10-fold reduction in hematologic ADRs among variant carriers who were identified and received a dose reduction, compared with variant carriers who did not, without differences in treatment efficacy. ClinicalTrials.gov number: NCT00521950.

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Immunohistochemistry of the S phase related proliferating cell nuclear antigen (PCNA) was studied as an alternative to ex-vivo bromodeoxyuridine (BrdU) immunohistochemistry for assessment of human colonic cell proliferation. From 16 subjects without colonic disease biopsy specimens were collected from five different sites along the colorectum and processed for BrdU Materials and methods BIOPSY SPECIMENSBiopsy specimens of endoscopically normal colonic mucosa were taken at five different sites from proximal to distal in the colorectum (ascending, transverse, and descending colon, sigmoid, and rectum) of 16 subjects who had had diagnostic colonoscopy because of abdominal complaints and who were found not to have any organic colonic disorders (seven men, nine women, mean age 49 years, range 17 to 76). All specimens were taken by one endoscopist (LGJBE) and completely processed by the same technician (AP-H). Specimens were immediately placed in RPMI 1640 tissue culture medium containing 10% fetal calf serum, 20 [1M 5-fluoro-uracil, 20 FM bromodeoxyuridine (Serva, Heidelberg, Germany), and 0 9% hydrogenperoxide during one hour at 37°C.The composition of the tissue culture medium was based on a 3 x 3 experiment in which optimal conditions for ex vivo labelling of mouse and human tissue with BrdU were determined. Intestinal specimens were incubated in RPMI 1640 medium containing 10% fetal calf serum and concentrations of 1, 2 or 3x 10-) M BrdU and 0 5, 1 or 2 10-5) M 5-fluorouracil. We found that the addition of hydrogen peroxide seemed to improve the label uptake, therefore in this experiment hydrogen peroxide 30% was added to final concentrations of 0-3, 0-9, and 1-8% respectively. Specimens were immersion fixed in 70% ethanol for at least 24 hours. Best results with regard to immunoreactivity and morphology, were obtained by incubation with RPMI 1640 medium containing 10% fetal calf serum, 2x 10-) M 5-fluoro-uracil, and 0-9% hydrogen peroxide.As maximum incorporation of BrdU can be expected after depletion of the endogenous pool 530 on 12 May 2018 by guest. Protected by copyright.

Proper prospective pharmacokinetic studies of 6-mercaptopurine (6-MP) in inflammatory bowel disease (IBD) patients are lacking. As a result, conflicting recommendations have been made for metabolite monitoring in routine practice. The authors have evaluated 6-MP pharmacokinetics in IBD patients, including the genetic background for thiopurine methyltransferase (TPMT). Red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) and 6-methylmercaptopurine ribonucleotide (6-MMPR) concentrations were measured in 30 IBD patients at 1, 2, 4, and 8 weeks after starting 6-MP, 50 mg once daily. Outcome measures included mean 6-TGN and 6-MMPR concentrations (+/- 95% confidence interval, CI95%) and their associations with TPMT genotype, 6-MP dose, and hematologic, hepatic, pancreatic, and efficacy parameters during the 8-week period. Steady-state concentrations were reached after 4 weeks, indicating a half-life of approximately 5 days for both 6-TGN and 6-MMPR; the concentrations were 368 (CI95% 284-452) and 2837 (CI95% 2101-3573) pmol/8 x 10 RBCs, respectively. Large interpatient variability occurred at all time points. TPMT genotype correlated with 6-TGN concentrations (0.576, P < 0.01), and patients with mutant alleles had a relative risk (RR) of 12.0 (CI95% 1.7-92.3) of developing leukopenia. A 6-MMPR/6-TGN ratio less than 11 was associated with therapeutic efficacy. Based on this pharmacokinetic analysis, therapeutic drug monitoring is essential for rational 6-MP dosing.

SUMMARY BackgroundMicroscopic colitis causes chronic watery diarrhoea. Recent studies have suggested an aetiological role for various medications, including proton pump inhibitors, in the pathogenesis of microscopic colitis.