Usefulness of thiopurine methyltransferase and thiopurine metabolite analysis in clinical practice in patients with inflammatory bowel diseases

Thiopurines (TP) are widely used in the management of inflam- matory bowel diseases. Side-effects and inefficacy are a major con- cern as they lead to withdrawal of the drug. Tools investigating TP metabolism are useful to avoid inadequate cessation of TP thera- py. TP metabolism is complex and many enzymes are involved. Among them, Thiopurine methyltransferase (TPMT) is the only one routinely measured by pheno- or genotyping. In this review, the rationale for TPMT and thiopurine metabolites, 6-thioguanine nucleotides and 6-methylmercaptopurine, determination in clini- cal practice is discussed, specifically in case of thiopurine failure and recommendations are given about their interpretation and potential dose optimization of TP drugs. (Acta gastroenterolog. belg., 2010, 73, 331-335).