Assay of 6-mercaptopurine and its metabolites in patient plasma by high-performance liquid chromatography with diode-array detection

A reversed-phase high-performance liquid chromatography (HPLC) method was d eveloped to determine 6-mercaptopurine (MP) and seven of its metabolites (6 -thioguanine, 6-thioxanthine, 6-mercaptopurine riboside, 6-thioguanosine, 6 -thioxanthine riboside, 6-methylmercaptopurine and 6-methylmercaptopurine r iboside) simultaneously in human plasma. A volume of 100 mu l of plasma was used. Protein was removed from the sample by a simple and easy ultrafiltra tion step and ultrafiltrate was directly injected onto the HPLC system. Ana lytes were detected and confirmed with a diode-array detector before quanti tation at 295 and 330 nm. The limit of detection for the analytes ranged fr om 20 to 50 nM. For the majority of patients receiving a 1 g/m(2) MP intrav enous infusion, MP and all metabolites except 6-thioguanine and 6-methylmer captopurine riboside were present. This method serves as useful tool to cha racterize pharmacokinetics and pharmacodynamics of MP in oncology patients, and the small volume of plasma lends itself to pediatric studies. (C) 1999 Published by Elsevier Science BN. All rights reserved.