Analytical Method Development and Validation and Forced Degradation Stability-Indicating Studies of Favipiravir by RP-HPLC and UV in Bulk and Pharmaceutical Dosage Form

Aims: To develop and validate a new, simple, rapid, precise, and accurate An Eco-friendly RPHPLC and UV-Method Development and Validation for an estimation of Favipiravir in Bulk and pharmaceutical dosage form followed by Forced Degradation Studies. Study Design: This was employed for UV-visible (200-400 nm and 400-800 nm respectively) and RP-HPLC method development using C 18 inertsil column and optimization of variables for Favipiravir estimation in bulk and formulations. Place and Duration of the Study: The present work was carried out at Ali-allana College of Pharmacy, Akkalkuwa between the duration of November-2020 to February-2021. Methodology: UV-Spectroscopic method was developed for the estimation of Favipiravir in the bulk and pharmaceutical dosage form. The solvent selected for the Favipiravir UV analysis was water, the solution in a range of 2-10μg/ml was scanned in the UV region from 200-400 nm and the λmax value was determined. The RP-HPLC method was developed on inertsil ODS-3V C18 150 mm x 4.6mm x 5μ column using buffer pH 3.5: acetonitrile [90:10] as mobile phase at flow rate 1.0 ml/min and PDA detection at 358 nm. Original Research Article Ali et al.; JPRI, 33(48B): 254-271, 2021; Article no.JPRI.76358 255 Results: The maximum absorbance was observed at 358 nm. The wavelength 358 nm was selected for further analysis of Favipiravir. The calibration curve was determined using drug concentrations ranging from 2-10 μg/ml. The % recovery for accuracy was 100.50-100.76%. The method was to be precise with a % RSD value 0.51-1.37 and 0.77-1.78 for intraday and Interday respectively. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 0.0723 &0.219 μg/ml respectively by UV method. The RP-HPLC method was shown to be linear in the 50250 μg/ml concentration range. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 2.186 & 6.626 μg/ml respectively. The method was to be precise with a % RSD value 0.25-1.53 and 0.86-1.68 for intraday and inter-day respectively. Conclusion: Here we conclude that the developed UV and RP-HPLC methods are precise, accurate, sensitive, and reproducible for the quantitative estimation of Favipiravir bulk and its formulation. The developed method can be used by the pharmaceutical industries for the routine analysis of Favipiravir, in particular by UV and RP-HPLC. The main features of the proposed method are economic and eco-friendly with less retention time around 5.0 min.


INTRODUCTION
Favipiravir (6-fluoro-3-hydroxypyrazine-2carboxamide), a purine nucleic acid analog developed by Toyama Chemical in Japan for the treatment of viral infections, including influenza. This has recently been evaluated and found to be a promising option in the management of COVID-19. It works by inhibiting the RNAdependent enzyme RNA polymerase (Rd-Rp), a key enzyme that prevents the replication of RNA viruses [1].
Favipiravir (T-705; 6-fluoro-3-hydroxy-2-pyrazine carboxamide) is an antiviral agent that selectively and potently inhibits RNA-dependent RNA polymerase (RdRp) of RNA viruses. Toyama Chemical Co. Ltd. discovered Favipiravir by examining a chemical library for antiviral activity against the influenza virus. Recognized as a substrate by RdRp and inhibits RNA polymerase activity [1,2]. As the catalytic domain of RdRp is conserved among various types of RNA viruses, this mechanism of action supports a broader spectrum of antiviral activities than Favipiravir. Favipiravir is effective against a wide range of influenza virus types and subtypes, including strains resistant to existing influenza drugs. Of note, Favipiravir exhibits antiviral activity against other RNA viruses such as arenavirus, bunyavirus, and filovirus, all of which are known to cause fatal hemorrhagic fever. These unique antiviral profiles will make Favipiravir a potentially promising drug for specifically intractable viral RNA infections [1,3].
Favipiravir has great utility for treating patients with COVID-19. However, research examining the efficacy and safety of Favipiravir for COVID-19 patients is limited. Favipiravir induces viral spread after 7 days and contributes to clinical improvement in 14 days. The results indicated that Favipiravir has a strong ability to treat COVID-19, especially in patients with mild to moderate disease. Further well-designed studies, including examinations of dose and duration of treatment, are critical to reaching firm conclusions [3,4].
Jyothi and Kavya developed only and single UV method on Favipiravir and concluded that given spectrophotometric method for the estimation of new antiviral repurposing drug Favipiravir as there is no reported simple UV spectrophotometric method for estimation. The efforts were made for development and validation of Favipiravir as per ICH guidelines, because drug has a wide scope for formulations to be developed for treating different viruses [5].
Dikma Technologies developed a simple HPLC-UV method for simultaneous analysis of ivermectin, molnupiravir, remdesivir, favipiravir and ritonavir Diamonsil® Plus C18 Column.Varma et al.concluded that developed RP-HPLC method is linear, accurate, precise, and robust. So, the developed method can be used for quality control, routine analysis and stability study of Favipiravir in single component without any interference from common excipients and impurity.Bulduk developed HPLC-UV method and revealed he ultraviolet (UV) detection and column temperature were 323 nm, and308C, respectively. The run time was 15 min under these chromatographic conditions. Excellent linear relationship between peak area and Favipiravir concentration in the range of 10-100mg/ml has been observed [6].
Nadendla and Patchala developed HPLC method by PDA detector concluded that The proposed method was successfully applied for the marketed formulations of Favipiravir tablets. In addition the main features of the proposed method are economic and eco-friendly with less retention time around 4.622 min [7].
A stability indicator test method can be defined as a "validated quantitative analytical method capable of detecting the change over time in the chemical, physical or microbiological properties of the pharmaceutical substance and specific pharmaceutical products so that the content of active ingredients and degradation products can be accurately measured without interference. The goal of this work is to develop and validate analytical methods for stability indicators for selected drugs and bulk formulations with forced degradation studies along with characterization [8].
Although many methods have been reported on the quantitative and qualitative estimation of Favipiravir in bulk and its commercial formulation, very little work has been done on its estimation by RP-HPLC followed by methods with stability indicators. The advantage of proposed method over other methods is that given method give less retention time (ecofriendly) with good resolution.Therefore, in the present work, we have developed and validated the selective stability indicated by the RP-HPLC and UV methods. The proposed methods were validated according to the ICH guidelines [1,8]. The structure of Favipiravir is depicted in Fig. 1.

Instruments
Shimadzu HPLC system [LC-20AD Multi-solvent delivery system, SPD-20A, PDA Detector, LC solution software] UV-Visible Spectrophotometer [Shimadzu-1800 double beam, with UV Probe 2.33].Labman sonicator was usedforsonication of the sample solution. Thermo scientific pH meter was used to measure pH. A vacuum pump filter was used for the filtration of mobile phase solvents.

Chemicals and Reagents
The drug was procured from Honour Lab, Hetero Limited with the certificate of analysis. The marketed formulation [Favipiravir tablet (Fabi flu) 200mg] was purchased from Blue Cross Laboratories Pvt. Ltd. Acetonitrile, HPLC grade water, Orthophosphoric Acid, Potassium Dihydrogen Phosphate, and Tri-ethylamine was procured from research lab fine chem industry.

SPECTROPHOTOMETRIC CONDITIONS
The stock solution was suitably diluted with distilled water, to get 10 μg/ml of Favipiravir. This solution was scanned in the UV region (200-400 nm) and found that Favipiravir exhibited maximum absorbance at about 358 nm as shown in Fig. 2.Hence 358 nm was selected for the proposed study [9,10].

Preparation of standard stock solution
The spectral pattern and absorbance maxima of Favipiravir were thoroughly analysed. It was found that significant spectra of Favipiravir appeared in distilled water and this solvent was selected for determining Favipiravir content in formulation by UV spectroscopic method. A stock solution of Favipiravir was prepared by dissolving 100mg of drug in 100ml of distilled water to obtain the concentration of 1000μg/ml. And from this 0.1ml was taken and transferred to a 100ml volumetric flask and diluted with distilled water to get 10µg/ml solutions [10,6].

Determination of standard calibration curve
Adequate dilutions were made from the stock solution to get a concentration ranging from 2-10 μg/ml for Favipiravir using distilled water. The absorbance of these solutions was measured at358nm. The absorbance values are tabulated. The measured absorbance was plotted against concentration. From the graph, it was found that the Beer's law concentration for Favipiravir lies between 2-10 μg/ml [6].

Chromatographic conditions
Chromatographic analysis was performed on a column of Inertsil ODS-3V C18. The mobile phase consisted of potassium dihydrogen phosphate 50 mM (pH 3.5) and acetonitrile (90:10, v/v). The mobile phase was filtered and degassed through a 0.45 mm membrane filter before use and then pumped at a flow rate of 1 ml/min.The run time was 10 min under these conditions as shown in fig.3 [11,12].

Preparation of buffer, mobile phase, and diluents
1.36gm of potassium dihydrogen phosphate and 2ml of triethylaminewere transferred into a beaker containing 1000ml of water and sonicated to dissolve the contents completely. The pH was adjustedto 3.5±0.05 with Orthophosphoric acid and mixed and filtered through 0.45µ filter paper [13].

Preparation of diluent
The degassed mixture of buffer and acetonitrile in50:50%v/v ratio was prepared.

Mobile phase
Select the Binary method in HPLC and select the pump B ratio as 90.

Preparation of standard stock solution
One hundred milligrams pure drug was accurately weighed, dissolved in about 30 mL of diluent, and transferred to a 100 mL volumetric flask. Then the volume was completed to 100 mL with diluent to obtain1000 mcg/mL of stock solution.

Preparation of stock for the stability study
For forced degradation 10mg of Favipiravir standard drug were weighed and transferred to 100 ml volumetric flask containing 70 ml of diluents, sonicated for 5 min, and the volume was made up to the mark with diluents [10, 14-15].

Linearity
Favipiravir was found to be linear in a concentration range of 2-10μg/ml. The absorbance of this solution was measured at 358 nm and a calibration graph was plotted using absorbance versus concentration.

Precision
The reproducibility was determined by repeating the above methods at different time intervals (morning, afternoon, and evening) on the same day (Intraday precision) and on three consecutive days (Interday precision). The intraday and inter-day variation for the estimation of Favipiravir was carried out at three different concentration levels of 2, 8, and 12 g/ml.

Accuracy
Accuracy was determined by performing recovery studies by spiking different concentrations of pure drug in a pre-analyzed sample solution of 4μg/ml. To pre-analyzed sample solution, a known amount of working standard solution of Favipiravir (0.33, 0.42, and 0.48 ml of 100 μg/ml) was added in 10 ml volumetric flask and made up to mark with diluent which was at different level i.e. 80%, 100%, and 120%. The solutions were analyzed by the proposed method. Calculate the mean % recovery from peak areas obtained.

Repeatability
It was determined by analyzing the same solution of 8 μg/ml of Favipiravir standard solution repeatedly.

LOD
The LOD was estimated from the set of five calibration curves used to determine method linearity. The calibration curve was repeated for 6 times and the SD of the intercept was calculated then LOD was calculated as follow: Where, SD= the standard deviation of the y-intercept of 5 calibration curves. Slope= the mean slope of the 5 calibration curves

LOQ
The LOQ was estimated from the set of five calibration curves used to determine method linearity.
The LOQ may be calculated as: Where, σ = Standard deviation of the Yintercepts of the five calibration curves. S = Mean slope of the five calibration curves [14,15].

Quantification of Favipiravir in Formulation
Ten Favipiravir tablets were accurately weighed and transferred to a dry and clean mortar, then grind into a fine powder, weighed tablet powder equal to 100mg transferred to 100ml of the volumetric flask containing distilled water of 30ml and sonicated for 15 min to dissolve the drug and volume made up to the mark with water (1000µg/ml), then 10ml from this solution was transferred to 100ml of volumetric flask and diluted up to the mark with water this gives 100 µg/ml. From the above solution, 2 ml of contents was transferred to 10ml of the volumetric flask to make 20µg/ml.
The data of the Favipiravir assay is tabulated, Beer-Lamberts law will be expressed as:

A= abc
Where, A=specific absorbance =358nm a=absorptivity or extinction coefficient b=path length of radiation through the sample (cm) c=concentration of solute in solution [15 , 2].

Linearity
Standard calibration has been prepared using 5 standard solutions within the concentration range of 50-250 μg/ml. In optimized chromatographic conditions, each standard solution was chromatograph for 10 min three times. Least squares linear regression analysis of theaverage peak area versus concentration data were used to evaluate the linearity of the method.The linearity for Favipiravir was assessed by analysis of standard solution in a range of 50-250 μg/ml [15,2,16].

Precision
Precision was analyzed by calculating variations of the method in intraday (repeatability performed by analyzing standard solution on the same day) and inter-day (repeatability carried out by analyzing standard solution on three different days). A precision study was performed by injecting six times of standard solution at three different concentrations 50, 100, and 150µg/ml on the same day and three consecutive days.
Results are expressed as relative standard deviation (RSD) or the coefficient of variance.

Accuracy
Accuracy was determined by performing recovery studies by spiking specific concentrations of pure drug in a pre-analyzed sample solution of 50μg/ml of Favipiravir. To preanalyze the sample solution, a known amount of standard stock solution was added which was at different levels 50, 100, and 150%. The solutions were analyzed by the proposed method. The mean % recovery was calculated.

Repeatability
It was determined by analyzing the same solution of 150 μg/ml of Favipiravir standard solution repeatedly.

Robustness
In the robustness study, the following parameters have been changed one by one and observed their effect on system suitability test and assay. i.
Change mobile phase composition by ± 1.0mL of organic solvent. ii.

Change in mobile phase composition
Standard the working solution was injected three times by change in the mobile phase composition by ±1.0 mL of organic solvent (phosphate buffer pH 3.5: acetonitrile) (89:11v/v and 91:09v/v) of the developed method.

Change in pH
Standard the working solution was injected three times by change in the pH by ± 1 of the sample (3.4, 3.5 and 3.6) of the developed method.
Calculate the % RSD of the mean area for change in the method parameter.

Change in flow rate
Standard the working solution was injected three times by change in the flow rate by ± 0.1 mL/min (0.9 mL/min and 1.1mL/min) of the developed method. Calculate the %RSD of mean area for change in method parameter [17][18][19].

Preparation of Standard Solution for Assay
Accurately weigh and transfer about 48mg of Favipiravir API into a 100ml volumetric flask.Add about 80ml of diluent and sonicate to dissolve. Dilute to volume with the diluent and mix. Transfer 5ml of above solution into a 50ml volumetric flask,dilute to volume with diluent, and mix.

Solution Stability of Favipiravir
The stability of the analytical solution was verified by analyzing the standard and filtered sample solution initially and also at different time intervals as mentioned below by storing it in the sample compartment of the HPLC instrument at ambient conditions. Calculated the cumulative percentage RSD for peak areas of Favipiravir for both the sample and standard solution [10, 15, and 19,20,3,4].

Acid degradation
From the test stock solution, 1 ml was taken in a 10 ml volumetric flask, adds 1 ml of 1N HCl, and heated at 60 0 C for 30 min on a water bath. The flask was removed from the water bath and allowed to cool at room temperature. Add 1 ml of 1N NaOH to neutralize the solution and diluted to volume with diluents and mix 10 ml solution were injected into the system and the chromatograms were recorded to assess the stability of the sample [10].

Alkali degradation
From the test stock solution, 1 ml was taken in a 10 ml volumetric flask, adds 1 ml of 1 N NaOH, and heated at 70 0 C for 1 h on a water bath. The flask was removed from the water bath and allowed to cool at room temperature. Add 1 ml of 1N HCl to neutralize the solution and diluted to volume with diluents and mix 10 ml solution were injected into the system and the chromatograms were recorded to assess the stability of sample [10].

Peroxide (oxidation) degradation studies (3%v/v of H 2 0 2 )
From the test stock solution, 1 ml was taken in a 10 ml volumetric flask add 1ml of 3% H 2 O 2 , and heated at 70 0 C for1 an hour on a water bath. The flask was removed from the water bath and allowed to cool at room temperature and diluted to volume with diluents and mixed, 10 ml solution were injected into the system and the chromatograms were recorded to assess the stability of the sample [15].

Photolytic degradation
From the test stock solution, 1 ml was taken in a 10 ml volumetric flask, add 5 ml of water, and sonicated to disperse, dissolve, and heated at 70 0 C for 3 h on a water bath. The flask was removed from the water bath and allowed to cool at room temperature and diluted to volume with diluents and mixed. 10 ml solution was injected into the system and the chromatograms were recorded to assess the stability of the sample [15].

Thermal degradation studies
For the Thermal Degradation 10 mg, Favipiravir, and drug samples were weighed accurately and transfer to the petridish Heat the sample in the oven for about 24h at 70 0 C and transfer the sample into a 100 ml volumetric flask dissolve and dilute to volume with diluents. Filter the solution using a 0.45m Nylon filter. Transfer 1ml of above stock solution to 10 ml volumetric flask and make up the volume with diluents to get the concentration of 10 mcg Favipiravir solution was injected into the system and the chromatograms were recorded to assess the stability of the sample [10,15].

Linearity
The linearity studies have been performed by scanning the solution of different concentrations from 2-10 μg/ml. The absorbance, standard deviation, and % RSD were calculated as shown in Table 1. The linearity curve suggests the perfect variation in absorbance value as increased in concentration. A calibration curve was plotted using absorbance versus concentration [ Fig. 4]. The correlation coefficient value was found to be 0.990 [10,15].

Precision
A precision study has been performed to check the reproducibility of the results of the developed method. In precision, the solution of Favipiravir (2, 8, and 12 μg/ml) was scanned at 358 nm on the same day but at a different time and on different three days. The results obtained are tabulated in Table 2. From the precision study, it was confirmed that the method is reproducible and selective enough [6].

Accuracy
The accuracy of the method was checked by a recovery experiment performed at three different levels, i.e., 80%, 100%, and 120%. The % recovery was found to be in the range of 99.99-100.76%. The low values of % RSD are indicative of the accuracy and reproducibility of the method in Table 3.

Repeatability
The low values of % RSD are indicative of the accuracy and reproducibility of the method. The repeatability of the method was determined by analyzing the same solution of 8 μg/ml of Favipiravir standard solution repeatedly in Table  4 [6].

Limit of Detection [LOD] and Limit of Quantification [LOQ]
Limit of Detection [LOD] and Limit of Quantification [LOQ] of the developed method has been studied in Table 5. It was found in the permissible range i.e. LOD, 0.0723, and LOQ, 0.219μg/ml.

Quantification of Favipiravir in Formulation
The λmax was observed exactly at 358 nm and the % assay was found to be 102% [Fig. 5]. The label claim of the Favipiravir was 200 mg and we found it to be 204 mg in the tablet assay of Favipiravir using this developed method in Table  6 [6,2].

Linearity
The linearity has been performed by determining a standard calibration curve using a concentration range of 50-250 μg/ml.Least squares linear regression analysis of the average peak area versus concentration data were used to evaluate the linearity of the method. The values obtained were linear correlation coefficient for calibration curve was found to be 0.996 in Fig. 6 and Table 7.

Precision
Precision was analyzed by calculating variations of the method in intraday (repeatability performed by analyzing standard solution on the same day) and inter-day (repeatability carried out by analyzing standard solution on three different days). The precision study showed the very closeness of the results in Table 8.

Accuracy
Accuracy was determined by performing recovery studies by spiking specific concentrations of pure drug in a pre-analyzed sample solution of 50μg/ml of Favipiravir. To preanalyze the sample solution, a known amount of standard stock solution was added which was at different levels 50, 100, and 150%. The % recovery was found to be between 99.99-100.42% [Table 9], which is the acceptable limit as per the ICH guidelines.

Repeatability
The low values of % RSD are indicative of the accuracy and reproducibility of the method. The repeatability of the method was determined by analyzing the same solution of 150 μg/ml of Favipiravir standard solution repeatedly in Table  10.

Limit of Detection (LOD) and Limit of Quantification (LOQ)
Limit of Detection (LOD) and Limit of Quantification (LOQ) of the developed method has been studied. It was found in the permissible range i.e. LOD, 2.186 and LOQ, 6.626μgm/ml tabulated in Table 11.

Robustness
The robustness of the developed method has been studied by changing mobile phase composition, altering the pH of the solvent system, and changing the flow rate. The % RSD of the robustness was found to be within permissible amount i.e. 0.28 to 1.46 in Table 12.

Analysis of Marketed Formulation using Developed HPLC Method
This developed RP-HPLC method has been applied to the marketed formulation of Favipiravir. The % of the assay was found to be 100.1% which is permissible as per the ICH guidelines in Table 13.The chromatogram is shown in Fig. 7 and 8.
For the development of the Favipiravir UV spectroscopic method, distilled water was selected as the solvent. The solution of appropriate concentration was tested in a UV range of 200 to 400 nm. The maximum absorbance was observed at 358 nm and the same value was selected for further analysis. The UV spectra have been reported in fig. 6. The Favipiravir calibration curve was determined using concentrations of 2-10 µg / mL. The calibration curve increased absorbance as we increased the concentration and a standard slope was given. This developed UV spectroscopic method was validated according to ICH guidelines in terms of linearity, precision, accuracy, and repeatability and stability studies [1, 6, and 2].   [2]. Low RSD% values are indicative of the accuracy and reproducibility of the method. The repeatability of the method was determined by repeatedly testing the same 80 µg / ml Favipiravir standard solution. The limit of detection (LOD) and limit of quantification (LOQ) of the developed method were investigated. It was found in the allowable range, namely LOD, 0.0723, and LOQ, 0.219 μg/ml. The developed method was successfully applied for the estimation of Favipiravir in selected commercial formulations. The UV graph obtained is illustrated in Fig. 6. Λmax was observed at exactly 358 nm and the% dosage was found to be 102%. The label indication for Favipiravir was 200 mg and we found that it was 204 mg in the Favipiravir tablet study using this developed method [6].
A simple, accurate, precise, rapid, specific, sensitive, and selective method indicating the stability of RP-HPLC has been developed and validated for the estimation of bulk and tablet Favipiravir, according to ICH guidelines.
A wavelength of 358 nm was chosen for the development of the RP-HPLC method. The solvent system was optimized by testing different proportions of buffer pH 3.5: acetonitrile, after about 8 tests, the most optimized chromatogram buffer pH 3.5 was obtained: acetonitrile (90:10) at a flow rate of 1 ml/min with time retention of 5 minutes. The most optimized peak of Favipiravir is shown in Fig. 12. The optimized chromatographic conditions were the C18 column, with an injection volume of 20 µg/ml and a detection wavelength of 358 nm. This developed RP-HPLC method has been validated in terms of linearity, precision, accuracy, LOD, LOQ, and robustness.
Linearity was achieved by determining the standard calibration curve using a concentration range of 50-250 μg / mL. The precision was analyzed by calculating the variations of the method in intraday (repeatability carried out by analyzing the standard solution on the same day) and inter-day (repeatability carried out by analyzing the standard solution on three different days). The precision study showed a great closeness to the results. Accuracy was determined by performing recovery studies by adding a specific concentration of pure drug to a previously tested 50 µg/mL sample solution of Favipiravir. A known amount of standard stock solution was added to the previously analyzed sample solution which was at different levels 50, 100, and 150%. The recovery rate was found to be between 99.99 and 100.42%, which is an acceptable limit according to ICH guidelines. The LOD and LOQ were found to be 2,186 and 6,626 respectively. The robustness of the developed method was studied by modifying the composition of the mobile phase, altering the pH of the solvent system, and modifying the flow rate. The% RSD of robustness was found to be within the allowable amount, which is 0.28 to 1.46.
Solution stability studies were conducted with Favipiravir solution. The% RSD of the peak areas obtained was calculated against the standard and the Favipiravir sample solution. The% RSD of the standard solution was found to be between 0.44 and 0.87 and of the sample solution between 0.28 and 0.58. It indicates the stability of the analytical solution.
Stability indicator methods were studied for the developed method by applying forced degradation studies. Acid hydrolysis was performed using 1N HCl followed by neutralization using a 1N NaOH solution. 1N NaOH was used for alkaline hydrolysis and neutralized using a 1N HCl solution. The% degradation was calculated for forced degradation studies. Similarly, photolytic, thermal, and UV degradation was carried out. The lowest degradation of 3.57% was observed in water hydrolysis, while, for acid hydrolysis, it caused 39.64% degradation.
This developed RP-HPLC method was applied to the commercial formulation of Favipiravir. The% degradation of the study was found to be 100.1%, which is allowed under ICH guidelines. Therefore, we hereby conclude that the developed method is accurate, accurate, sensitive, and reproducible for the quantitative estimation of Favipiravir bulk and its formulation [6,11,12,15,2,16].

CONCLUSION
This developed UV spectroscopic method was validated according to ICH guidelines in terms of linearity, precision, accuracy, and repeatability and stability studies. All validation parameters were found to be within the allowable limit according to ICH guidelines. The developed method was successfully applied for the estimation of Favipiravir in selected commercial formulations. Here we conclude that the developed UV and RP-HPLC methods are precise, accurate, sensitive, and reproducible for the quantitative estimation of Favipiravir bulk and its formulation. The developed method can be used by the pharmaceutical industries for the routine analysis of Favipiravir, in particular by UV and RP-HPLC.

DISCLAIMER
The products used for this research are commonly and predominantly use products in our area of research and country. There is absolutely no conflict of interest between the authors and producers of the products because we do not intend to use these products as an avenue for any litigation but for the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by personal efforts of the authors.

CONSENT
It is not applicable.

ETHICAL APPROVAL
It is not applicable.