In-vivo implementation of the HPTLC methodology to rat plasma for the concurrent determination of a novel combination therapy for the management of COVID-19 (favipiravir and nitazoxanide).

The 2019 coronavirus outbreak has prompted scientists to investigate pharmaceuticals to prevent the spread of the disease. Favipiravir (FAV) has received Food and Drug Administration FDA approval for the treatment of various viral infections with notable efficacy in clinical trials for COVID-19. Nitazoxanide (NTZ) is a broad-spectrum antiparasitic and antiviral agent used for the treatment of parasitic illnesses. Recently, the antiviral medications FAV and NTZ have been utilized therapeutically as early antiviral combination therapy for COVID-19, highlighting their safety, efficacy, and immunomodulatory effects. Despite several clinical studies on both FAV and NTZ, no analytical method has been developed for their concurrent detection. The objective of this study is to develop a TLC-densitometric method for their assessment and application to rat plasma. FAV, NTZ, and tizoxanide (the active metabolite of nitazoxanide (TZM)) were simultaneously determined using an HPTLC method embracing sulfasalazine as an internal standard (IS). Silica gel 60 F254 used as the stationary phase for chromatographic separation, the mobile phase consisted of chloroform-methanol-formic acid (9.5:0.5:0.2, v/v/v), with UV detection at 230 nm demonstrating linearity within the range of 0.5-5 μg/band. The proposed methodology has been shown to effectively measure the analyzed elements in both pure form and in-vivo rat plasma.