BACKGROUND AND PURPOSE: Although 6-mercaptopurine and azathioprine are effective treatments in inflammatory bowel disease (IBD), many patients discontinue treatment because of side effects. 6-Thioguanine (6-TG) may be an alternative rescue therapy in these intolerant patients but the pharmacokinetics of 6-TG are not fully described. Here we have measured the pharmacokinetics of the biotransformation of 6-TG into the pharmacologically active metabolites, 6-thioguanine nucleotides (6-TGN), in IBD patients. EXPERIMENTAL APPROACH: In 12 patients with IBD, levels of 6-TGN and activities of thiopurine S-methyltransferase, xanthine oxidase and hypoxanthine guanine-phosphoribosyl-transferase were measured in a two-stage (i.v. and p.o. administration of 0.3 mg·kg(-1) 6-TG), prospective study. Median exposure of 6-TGN in red blood cells (RBC) was expressed as the ratio of the area under the curve (AUC) per mg 6-TG after i.v. dosing and that after p.o. dosing. KEY RESULTS: The median AUC per mg 6-TG was 1068 (p.o.) and 7184 (i.v.) pmol·h (8 × 10(8) RBC)(-1) . Median exposure of 6-TGN in RBC was 15% (9-28). Hypoxanthine guanine-phosphoribosyl-transferase activity correlated with peak 6-TGN and with AUC per mg (r= 0.7, P= 0.02 and r= 0.6, P= 0.03 respectively). Thiopurine S-methyltransferase activity was inversely related to AUC per mg (r=-0.8, P= 0.001), whereas that of xanthine oxidase was correlated with a lower peak 6-TGN (r=-0.7, P= 0.02). CONCLUSIONS AND IMPLICATIONS: The great variability of the AUC per mg for 6-TG observed after p.o. and i.v. administration of 6-TG, was partly explained by variability in activities of metabolizing enzymes. Exposure of 6-TGN was low in all patients.
BACKGROUND AND PURPOSE: Although 6-mercaptopurine and azathioprine are effective treatments in inflammatory bowel disease (IBD), many patients discontinue treatment because of side effects. 6-Thioguanine (6-TG) may be an alternative rescue therapy in these intolerant patients but the pharmacokinetics of 6-TG are not fully described. Here we have measured the pharmacokinetics of the biotransformation of 6-TG into the pharmacologically active metabolites, 6-thioguanine nucleotides (6-TGN), in IBD patients. EXPERIMENTAL APPROACH: In 12 patients with IBD, levels of 6-TGN and activities of thiopurine S-methyltransferase, xanthine oxidase and hypoxanthine guanine-phosphoribosyl-transferase were measured in a two-stage (i.v. and p.o. administration of 0.3 mg·kg(-1) 6-TG), prospective study. Median exposure of 6-TGN in red blood cells (RBC) was expressed as the ratio of the area under the curve (AUC) per mg 6-TG after i.v. dosing and that after p.o. dosing. KEY RESULTS: The median AUC per mg 6-TG was 1068 (p.o.) and 7184 (i.v.) pmol·h (8 × 10(8) RBC)(-1) . Median exposure of 6-TGN in RBC was 15% (9-28). Hypoxanthine guanine-phosphoribosyl-transferase activity correlated with peak 6-TGN and with AUC per mg (r= 0.7, P= 0.02 and r= 0.6, P= 0.03 respectively). Thiopurine S-methyltransferase activity was inversely related to AUC per mg (r=-0.8, P= 0.001), whereas that of xanthine oxidase was correlated with a lower peak 6-TGN (r=-0.7, P= 0.02). CONCLUSIONS AND IMPLICATIONS: The great variability of the AUC per mg for 6-TG observed after p.o. and i.v. administration of 6-TG, was partly explained by variability in activities of metabolizing enzymes. Exposure of 6-TGN was low in all patients.
Authors: P Deibert; K Dilger; C Fischer; U Hofmann; S Nauck; S Stoelben; W Kreisel Journal: Aliment Pharmacol Ther Date: 2003-07-15 Impact factor: 8.171
Authors: Jenneke J Keizer-Garritsen; Connie Brouwer; Lambert H J Lambooy; Patricia Ter Riet; Jos P M Bökkerink; Frans J M Trijbels; Ronney A De Abreu Journal: Ann Clin Biochem Date: 2003-01 Impact factor: 2.057
Authors: Ahmed B Bayoumy; Femke Crouwel; Nripen Chanda; Timothy H J Florin; Hans J C Buiter; Chris J J Mulder; Nanne K H de Boer Journal: Eur J Drug Metab Pharmacokinet Date: 2021-09-06 Impact factor: 2.441