Sensitive high performance liquid chromatographic assay for nitazoxanide metabolite in plasma

A sensible and specific HPLC analytical method for the determination of tizoxanide (TZO), the active metabolite of nitazoxanide (NTZ) in rat plasma was developed and validated. Samples of 200 microL were efficiently deproteinized with acetonitrile. Assay was performed using a C18 CC with a ternary gradient elution of 50 mmol x L(-1) KH2PO4 : acetonitrile : methanol and UV/Vis detection at 416 nm. The analytical method was linear in a range of 10-1280 ng x mL(-1), precise (RSD % > 2.2), accurate (RE % < 7.8) and with high recovery (% > 95%). Stability studies showed that TZO was stable in plasma for short and long-time period (45 days) and proved to be suitable for pharmacokinetic studies of NTZ in rats. The method was also evaluated using human plasma samples and no statistical differences were found in the response-curve between rat and human samples.