Azathioprine in the therapy of paediatric inflammatory bowel disease – part II: pharmacodynamics, pharmacokinetics, and the possibilities of measuring its metabolites in clinical practice

Summary Background: Thiopurines (predominantly azathioprine and mercaptopurine) are widely used in paediatrics to maintain remission in the treatment of inflammatory bowel disease. After its absorption from the gastrointestinal tract, azathioprine is converted into 6 mercaptopurine in approximately 90%. Several enzymes (such as thiopurine methyltransferase, xanthine oxidase and hypoxanthine-guanine phosphoribosyl transferase) participate in its further metabolism, producing non-active methylated metabolites (6 methylmercaptopurine) and thiouric acid and active 6-thioguanine nucleotide. The concentration of these metabolites can be measured in red blood cells. Aim: To map the benefits and possibilities of thiopurine metabolites measurements in patients suffering from inflammatory bowel disease. Conclusion: The measurement of active and non-active metabolites can help evaluate the bioavailability of those drugs, identify some causes of adverse effects and reveal non-adherence. Keywords Crohn’s disease, merkaptopurin, pediatrie, thiopuriny, ulcerative colitis