Metronidazole is a chromatographic interference on a routine HPLC-UV assay for thiopurine metabolites.

Background Thiopurine metabolites, 6-thioguanine (6TG) and 6-methylmercaptopurine (6MMP), are monitored to aid therapeutic management of thiopurine drugs. At Manchester University NHS Foundation Trust (MFT), thiopurine metabolites are measured by high performance liquid chromatography with ultraviolet detection (HPLC-UV). Whole blood samples are lysed and subjected to hydrolysis with derivatisation of 6MMP before HPLC-UV detection at 304nm for the 6MMP-derivative and 342nm for 6TG.