Objective: The aim of this study is to assess the relationship between TPMT activity and 6-thioguanine nucleotide
(6-TGN) and 6-methylmercaptopurine ribonucleotide (6-MMPN) levels in patients with 11313 in clinical practice.
Differences in nucleotide hydrolysis contribute to the differences between erythrocyte 6-thioguanine nucleotide
concentrations determined by two widely used methods.
Azathioprine metabolism: pharmacokinetics of 6-mercaptopurine, 6-thiouric acid and 6-thioguanine nucleotides in renal transplant patients.
Analysis of 6-mercaptopurine, 6-thioguanine nucleotides, and 6-thiouric acid in biological fluids by high-performance liquid chromatography.
If patients with a homozygous deficiency of TPMT are given thiopurine derivatives at a standard therapeutic oral dosage, 6-thioguanine nucleotides will accumulate, usually within 4-6 weeks, to toxic concentrations.
Pharmacokinetics of 6-thioguanine nucleotides under i.v.
 Nonstandard abbreviations: 6-TGN, 6-thioguanine nucleotide
; Me6-MP, 6-methylmercaptopurine; LC-MS, liquid chromatography--mass spectrometry; IR, infrared; NMR, nuclear magnetic resonance; and Me6-MPR, 6-methylmercaptoribonucleoside.
6-MP is further converted in the liver and gut to 6-thioguanine nucleotides
, the pharmacologically active metabolites, by several enzymes, including hypoxanthine guanine phosphoribosyltransferase.