A newly developed high-performance thin layer chromatographic method for determination of remdesivir, favipiravir and dexamethasone, in spiked human plasma: comparison with the published methods.

Co-administration of COVID-19 RNA polymerase inhibitors, remdesivir and favipiravir, has synergistic benefits. Together they reduce viral load and inflammation more effectively than either drug used alone. Corticosteroids like dexamethasone are used alongside antivirals in multidrug combination regimens. A new HPTLC method was utilized to isolate and quantitatively determine the three medicines of the COVID-19 therapeutic protocol, remdesivir, favipiravir and dexamethasone, using the anticoagulant apixaban as an internal standard in human plasma. The mobile phase system used a solvent mixture of ethyl acetate, hexane, and acetic acid (9:1:0.3, by volume). At 254 nm, well-resolved spots with Rf values of 0.3 for remdesivir, 0.64 for dexamethasone, and 0.77 for favipiravir have been observed. To ensure compliance with FDA regulations, a validation study was conducted. Quantitation limits as low as 0.1 µg/band have been achieved with remdesivir and dexamethasone, and 0.2 µg/band with favipiravir, demonstrating excellent sensitivities. From 97.07% to 102.77%, the drugs were recovered from human plasma that had been artificially spiked. The whiteness of the method has been assessed using RGB 12 algorithm and a percentage of whiteness of 95.6% has been obtained.