A systemic approach to estimate and validate RP-HPLC assay method for remdesivir and favipiravir in capsule dosage form

The implementation of quality by design offer quality and safety product to patients, efficient processes for continuous improvements to manufacturers, negligible amount of batch failures and robust product quality attributes. This study was designed to establish a simple, specific, precise, and accurate reverse phase-high performance liquid chromatographic (RP-HPLC) method for the quantitative determination of remdesivir and favipiravir in Capsule dosage forms. The RP-HPLC method was performed on a Kromasil 100A C18 column (250 mm x 4.6 mm, 5 μm particle size) with a mobile phase containing (50 mL of acetonitrile, 350 mL methanol, 100ml of water and 0.5 mL of Phosphoric acid). The flow rate was 1.0 mL/min. The ultraviolet (UV) detection wavelength was 300 nm, and the column temperature was set at ambient. Linearity and range stock solutions were prepared as 50% to 150%. The calibration curves showed a good linear response ranged from 0.02 to 0.06 mg/ml (r=1.0000) for favipiravir and 0.022 to 0.066 mg/ml (r=1.0000) for remdesivir, and the average recoveries were 99.9% for favipiravir and 99.8% for remdesivir in assay test. The retention time of favipiravir was RT 11.5 minutes and remdesivir 20.95 minutes, tailing factor was not more than 1.5 and resolution of more than 2.0 respectively. The extended run time was supported by high concentration of favipiravir and uneven peak behavior of remdesivir in single run, which disturb resolution, retention times, injection repeatability. Reducing runtime on HPLC will lead to coelution of peaks, poor resolution, and loss of sensitivity during degradation profiling. This issue may be overcome with future UHPLC technique. The method was validated in accordance to International Council for Harmonization of Technical Requirements of Pharmaceuticals for Human Use (ICH) guidelines. The limit of detection (LOD) for Favipiravir was 0.104mg/ml and Remdesivir was 0.052mg/ml and limit of quantification (LOQ) for Favipiravir was 0.316mg/ml and Remdesivir was 0.158mg/ml respectively. In stress conditions, this product undergoes degradation and was considered sensitive to Acid, Alkali, Oxidation, reduction, hydrolysis, high temperature and humidity. The assay methods was simple, rapid, sensitive, repeatable, eco-friendly, stability indicating and can be used cost-effectively for the testing of these two drug substances in capsule dosage form. Due to the emergent need of antivirals for flu management, this coloaded combination was considered as dire need of society. Also, we reported that the product must be stored under ambient temperature, low humidity, and protected from light exposure.