Advancements in Antiviral Therapy: Favipiravir Sodium in Nasal Formulation

Favipiravir (FPV) is an Active Pharmaceutical Ingredient (API) known to have lower solubility in aqueous solvents. In the current study, efforts were made to generate a crystalline Favipiravir Sodium Salt (NaFPV) for enhanced solubility in aqueous media. The in-house generated NaFPV was characterized by NMR studies and its sodium content was determined by Flame Emission Spectroscopy (FES) as a confirmation of salt formation. Its solubility was determined where-in the solubility of NaFPV in water was about 100 times greater than FVP. FPV and NaFPV nasal spray formulations were prepared and its activity was determined against human coronavirus (hCoV) 229E strain. In the anti-hCoV assay as compared to FPV, NaFPV showed almost threefold higher anti-viral activity than its unmodified counterpart. Accelerated stability and spray pattern characteristics of both the formulations were studied. Interestingly, NaFPV showed higher physical stability during storage at conditions 40 ± 2 °C/ 75% ± 5% RH. The nasal spray formulations of both FPV and NaFPV showed ideal plume geometry and spray pattern of acceptable specifications. Due to its improvement in terms of solubility, NaFPV will have higher rate and extent of absorption, and faster onset of the therapeutic effect and may appear to be a feasible alternative to regular favipiravir for use in solid dosage forms.