Development of a method by UPLC-MS/MS for the quantification of tizoxanide in human plasma and its pharmacokinetic application

Background: Nitazoxanide (NTZ) is used for the treatment of gastrointestinal tract colonization by anaerobic bacteria, viruses and other pathogens that represent a major cause of morbidity in Latin America. The aim of the present work was to develop and validate a UPLC-MS/MS method for the selective quantification of tizoxanide (TZN, the major metabolite of NTZ) in human plasma using niclosamide as internal standard; and examine its pharmacokinetic application in healthy volunteers. Nine male subjects received a single oral dose of a NTZ 500-mg tablet under fasting conditions. Results: The method was linear between 0.1 and 10 mu g/ml and capable of separating signals from free-TZN and those delivered by in-source collision-induced dissociation of TZN-glucuronide, quantifying it with accuracy and precision. Mean maximum plasma concentration was 6.79 mu g/ml and was reached at 2.4 h post-dose. Conclusion: The method was validated, fulfilling regulatory guidelines. Results suggest low pharmacokinetic variability in the assayed population.