Quantitative analysis of favipiravir and hydroxychloroquine as FDA-approved drugs for treatment of COVID-19 using synchronous spectrofluorimetry: application to pharmaceutical formulations and biological fluids

Fluorometric and colorimetric platforms for rapid and sensitive hydroxychloroquine detection in aqueous samples

The detection of pharmaceuticals has been an active area of research with numerous application areas ranging from therapeutic and environmental monitoring to pharmaceutical manufacturing and diagnostics. And, the emergence of COVID-19 pandemic has increased the demand for detection of certain active pharmaceutical ingredients such as Hydroxychloroquine (HCQ) mainly due to their increased manufacturing and usage. In this study, we present two optical, fluorometric and colorimetric, detection platforms for the rapid and sensitive detection of HCQ. These platforms take advantage of the interactions between the highly fluorescent dye Thioflavin T (ThT) and Tel24 G-quadruplex (G4) DNA structure, as well as the salt-induced aggregation behavior of negatively charged citrate-capped silver nanoparticles (Cit-AgNPs) in the presence of HCQ. In the fluorometric method, the addition of HCQ led to a significant and rapid decrease in the fluorescence signal of the ThT + Tel24 probe. In the colorimetric method, HCQ induced the aggregation of Cit-AgNPs in the presence of NaCl, resulting in a noticeable color change from yellowish-gray to colorless. Under the optimized conditions, the colorimetric platform exhibited a linear range of 18.0-240.0 nM and a detection limit of 9.2 nM, while the fluorometric platform showed a linear range of 0.24-5.17 μM and a detection limit of 120 nM. The selectivity of the proposed optical methods towards the target analyte was demonstrated by evaluating the response to other structurally similar small molecules. Finally, the practical applicability of both detection systems was confirmed by analyzing HCQ-spiked human urine samples that yielded average recoveries ranging from 75.4 to 110.2 % for the fluorometric platform and 86.9-98.2 % for the colorimetric platform. These results indicate the potential of the developed methods for HCQ detection in complex matrices.

Luminescence of favipiravir in skin appendages and sclera. A controlled study and literature review

BACKGROUND/OBJECTIVES

Favipiravir is an antiviral agent, recently used for COVID-19 infections. Several reports associate favipiravir intake with Wood's lamp fluorescence of hair, nails, and sclera. The present study was designed to elucidate the positivity rates, and sites of favipiravir-related fluorescence and to unravel the site-specific changes in fluorescence positivity rates by a function of time past exposure.

METHODS

The study population comprised 50 patients and 50 control individuals. All patients in the patient group had received a full dose of favipiravir for COVID-19 infection. Fifty volunteers served as the control group. Wood's lamp examination was performed in a completely darkened room, and the positivity rate, extent, pattern, and distribution of fluorescence were recorded.

RESULTS

Wood's light revealed fluorescence of the fingernails, toenails, sclera, and hair in 35 (70%), 35 (70%), 22 (44%), and 8 (16%) patients, respectively. No control individual tested positive by Wood's lamp. Statistical analysis revealed significant differences between patient and control groups in terms of Wood's light luminescence in the fingernails (p = .000), toenails (p = .000), sclera (p = .000) and hair (p = .003). Although fingernail, toenail, and hair fluorescence positivity rates declined or ceased at or after 91 days of favipiravir exposure, ocular fluorescence positivity rates were prolonged up to 188 days.

CONCLUSIONS

These findings confirm that favipiravir may produce fluorescence of nails, sclera, and hair, detectable by Wood's light starting from the initial month and peaking at second- and third months following exposure to the medication. Although nail and hair fluorescence tend to abate after 3 months, ocular fluorescence may persist even longer than 6 months after cessation of the medication.

A solvent-free HPLC method for the simultaneous determination of Favipiravir and its hydrolytic degradation product

During COVID-19 pandemic, Favipiravir (FPV) showed a great efficacy against COVID-19 virus, it produced noticeable improvements in recovery of the patients. The aim of this study was to develop a new, green and simple method for the simultaneous determination of FPV and its acid-induced degradation product (ADP) in its pure and pharmaceutical dosage forms. This method will be key for the inevitable development of FPV solution and inhaler formulations. A green micellar RP-HPLC method was developed using an RP-VDSPHERE PUR 100 column (5 µm, 250 × 4.6 mm) and an isocratic mixed micellar mobile phase composed of 0.02 M Brij-35, 0.1 M SDS and 0.01 M potassium dihydrogen orthophosphate anhydrous and adjusted to pH 3.0 with 1.0 mL min-1 flow rate. The detection was performed at 280 nm with a run time of less than six min. Under the optimized chromatographic conditions, linear relationship has been established between peak area and concentration of FPV and its ADP in the range of 5-100 and 10-100 µg mL-1 with elution time of 3.8 and 5.7 min, respectively. The developed method was validated according to the ICH guidelines and applied successfully for determination of FPV in its pharmaceutical dosage form.

Spectrophotometric determination of favipiravir in presence of its acid hydrolysis product

Favipiravir (FAV) has been approved as an antiviral drug used in pandemic corona virus to treat covid-19. It has an amide moiety susceptible to hydrolysis and degradation in acid medium. Therefore, four simple, sensitive, and accurate stability indicating spectrophotometric methods have been developed for the determination of FAV in presence of its acid induced degradation product. The first method describes direct determination of FAV at 323 nm. Dual wavelength method was the second developed one for FAV quantitation by recording the absorbance difference at 322.7 and 270 nm. The third method involves using first derivative peak to peak amplitude at 338.0 and 308.0 nm, while difference spectrophotometry was the fourth suggested method, and it was based on recording the spectral changes at 361.3 nm as pH changes. The obtained calibration curves were linear over 4.0-22.0 µg/mL. Accuracy of the suggested procedures ranged from 99.11 to100.06, while precision results were from 0.80 to1.68. The developed methods were used to determine FAV in pure powdered form, laboratory-prepared mixtures with their degradation product, and pharmaceutical formulation without interference from its acidic degradation product.The greenness was assessed based on GAPI and ACREE metric and was found to be compatible and in reconciliation with green analytical chemistry concepts.

Validated spectrofluorimetric assay of two co-administered drug mixtures containing hydroxychloroquine with either moxifloxacin or ofloxacin as a drug regimen for hospital-acquired pneumonia in patients with COVID-19

Moxifloxacin and ofloxacin are two broad-spectrum quinolone antibiotics. They are among the most widely used antibiotics, at this time, applied to control the COVID-19 pandemic. Hydroxychloroquine is an FDA-approved drug for the treatment of COVID-19. This work describes a simple, green, selective, and sensitive spectrofluorimetric method for the assay of moxifloxacin and ofloxacin in the presence of hydroxychloroquine, two co-administered mixtures used in the treatment of hospital-acquired pneumonia in patients with COVID-19. Simultaneous assay of hydroxychloroquine and moxifloxacin was carried out in methanol using a direct spectrofluorimetric method (method I) at 375 and 550 nm, respectively, after excitation at 300 nm. The direct spectrofluorimetric assay was rectilinear over concentration ranges 50.0-400.0 and 300.0-2500.0 ng/ml for hydroxychloroquine and moxifloxacin, respectively, with limits of detection (LOD) of 6.4 and 33.64 ng/ml and limits of quantitation (LOQ) of 19.4 and 102.6 ng/ml, respectively, for the two drugs. The assay for hydroxychloroquine and ofloxacin was carried out by measuring the first derivative synchronous amplitude for hydroxychloroquine at the zero crossing point of ofloxacin and vice versa at Δλ = 140 nm (method II). Hydroxychloroquine was measured at 266 nm, while ofloxacin was measured at 340 nm over the concentration range 4-40 ng/ml for hydroxychloroquine and 200-2000 ng/ml for ofloxacin with LOD of 0.467 and 25.3 ng/ml and LOQ of 1.42 and 76.6 ng/ml, respectively, for the two drugs. The two methods were validated following International Conference on Harmonization guidelines and were applied to the analysis of the two drugs in plasma with good percentage recoveries (109.73-93.17%).

Quantitative analysis of two COVID-19 antiviral agents, favipiravir and remdesivir, in spiked human plasma using spectrophotometric methods; greenness evaluation

Favipiravir and remdesivir have been included in the COVID-19 treatment guidelines panel of several countries. The main objective of the current work is to develop the first validated green spectrophotometric methods for the determination of favipiravir and remdesivir in spiked human plasma. The UV absorption spectra of favipiravir and remdesivir have shown some overlap, making simultaneous determination difficult. Due to the considerable overlap, two ratio spectra manipulating spectrophotometric methods, namely, ratio difference and the first derivative of ratio spectra, enabled the determination of favipiravir and remdesivir in their pure forms and spiked plasma. The ratio spectra of favipiravir and remdesivir were derived by dividing the spectra of each drug by the suitable spectrum of another drug as a divisor to get the ratio spectra. Favipiravir was determined by calculating the difference between 222 and 256 nm of the derived ratio spectra, while calculating the difference between 247 and 271 nm of the derived ratio spectra enabled the determination of remdesivir. Moreover, the ratio spectra of every drug were transformed to the first order derivative using ∆λ = 4 and a scaling factor of 100. The first-order derivative amplitude values at 228 and 251.20 nm enabled the determination of favipiravir and remdesivir, respectively. Regarding the pharmacokinetic profile of favipiravir (C_max 4.43 µg/mL) and remdesivir (C_max 3027 ng/mL), the proposed methods have been successfully applied to the spectrophotometric determination of favipiravir and remdesivir in plasma matrix. Additionally, the greenness of the described methods was evaluated using three metrics systems: the national environmental method index, the analytical eco-scale, and the analytical greenness metric. The results demonstrated that the described models were in accordance with the environmental characteristics.

Synchronous spectrofluorimetric determination of favipiravir and aspirin at the nano-gram scale in spiked human plasma; greenness evaluation

Favipiravir and aspirin are co-administered during COVID-19 treatment to prevent venous thromboembolism. For the first time, a spectrofluorometric method has been developed for the simultaneous analysis of favipiravir and aspirin in plasma matrix at nano-gram detection limits. The native fluorescence spectra of favipiravir and aspirin in ethanol showed overlapping emission spectra at 423 nm and 403 nm, respectively, after excitation at 368 nm and 298 nm, respectively. Direct simultaneous determination with normal fluorescence spectroscopy was difficult. The use of synchronous fluorescence spectroscopy for analyzing the studied drugs in ethanol at Δλ = 80 nm improved spectral resolution and enabled the determination of favipiravir and aspirin in the plasma matrix at 437 nm and 384 nm, respectively. The method described allowed sensitive determination of favipiravir and aspirin over a concentration range of 10-500 ng/mL and 35-1600 ng/mL, respectively. The described method was validated with respect to the ICH M10 guidelines and successfully applied for the simultaneous determination of the mentioned drugs in pure form and in the spiked plasma matrix. Moreover, the compliance of the method with the concepts of environmentally friendly analytical chemistry was evaluated using two metrics, the Green Analytical Procedure Index and the AGREE tool. The results showed that the described method was consistent with the accepted metrics for green analytical chemistry.

Micellar-enhanced and green-assessed first-derivative synchronous spectrofluorimetric approach for concurrent determination of alfuzosin hydrochloride and solifenacin succinate in different matrices: Docking simulation

Alfuzosin hydrochloride (AZH) is co-formulated with solifenacin succinate (SOS) in Solitral® capsules for treating prostate hyperplasia in patients with overactive bladder syndrome. Herein and for the first time, an ultrasensitive synchronous spectrofluorimetric approach coupled with first-order derivative signal processing was designed for simultaneous determination of AZH and SOS in their pure forms, newly-released pharmaceutical capsules, and human biological fluids. AZH and SOS showed their conventional emission spectra in bi-distilled water at 382 nm and 294 nm after excitation at 325 nm and 250 nm, respectively. The native fluorescence intensities of AZH and SOS were greatly enhanced through micellar formation using sodium dodecyl sulfate surfactant (2%). The proposed approach included the use of synchronous mode at Δλ of 60 nm where the overlap between the studied analytes' fluorescence spectra wasn't completely resolved. The complete resolution was achieved by derivatization of the synchronized spectra to the first-order yielding two zero-crossing points which allowed the determination of AZH and SOS simultaneously without interference at 408 nm and 321 nm, respectively. Under optimum experimental circumstances, good linearities were accomplished over the concentration ranges of (1-24) ng/mL and (4-250) ng/mL with LOD of 0.26 ng/mL and 1.31 ng/mL for AZH and SOS, respectively. The proposed approach was validated successfully according to guidelines adopted by the ICH and compared statistically with the reported LC method with no discernible differences concerning accuracy or precision at p = 0.05. Successful application of the proposed approach achieved with excellent recovery percentages for analysis of the studied analytes in different matrices (pharmaceutical capsules and biological fluids) confirms its suitability for use in QC laboratories and other bioanalytical applications. The proposed approach's greenness was evaluated using two tools namely; penalty points scoring system and green analytical procedure index (GAPI) divulging excellent greenness of this approach relative to the reported LC method. The proposed approach relied chiefly on water as the cheapest and greenest solvent.

An Innovative Polymer-Based Electrochemical Sensor Encrusted with Tb Nanoparticles for the Detection of Favipiravir: A Potential Antiviral Drug for the Treatment of COVID-19

An innovative polymer-based electro-sensor decorated with Tb nanoparticles has been developed for the first time. The fabricated sensor was utilized for trace determination of favipiravir (FAV), a recently US FDA-approved antiviral drug for the treatment of COVID-19. Different techniques, including ultraviolet-visible spectrophotometry (UV-VIS), cyclic voltammetry (CV), scanning electron microscope (SEM), X-ray Diffraction (XRD) and electrochemical impedance spectroscopy (EIS), were applied for the characterization of the developed electrode TbNPs@ poly m-THB/PGE. Various experimental variables, including pH, potential range, polymer concentration, number of cycles, scan rate and deposition time, were optimized. Moreover, different voltammetric parameters were examined and optimized. The presented SWV method showed linearity over the range of 10-150 × 10-9 M with a good correlation coefficient (R = 0.9994), and the detection limit (LOD) reached 3.1 × 10-9 M. The proposed method was applied for the quantification of FAV in tablet dosage forms and in human plasma without any interference from complex matrices, obtaining good % recovery results (98.58-101.93%).

Spectrofluorimetric quantitative analysis of favipiravir, remdesivir and hydroxychloroquine in spiked human plasma

Favipiravir, remdesivir and hydroxychloroquine have been suggested in COVID-19 Treatment Guidelines Panel of many countries. Synchronous spectrofluorometric measurement provides sensitive tool for resolving the overlapped spectra of multicomponent drugs through converting the wider spectra to narrower sharp spectra. This work introduces the first fluorescence spectroscopic method for quantitative analysis of favipiravir, remdesivir and hydroxychloroquine in spiked human plasma. Testing the fluorescence spectra of favipiravir, remdesivir and hydroxychloroquine shows severe overlap, which hinders the direct quantification of the cited drugs. To overcome the overlapping issue, the drugs under the study have been measured in the synchronous mode at Δλ = 60 nm. Favipiravir could be measured directly at 423 nm without interference of remdesivir or hydroxychloroquine. Synchronous measuring the cited drugs at Δλ = 130 nm with mathematical transforming to the first order derivative spectra allowing remdesivir and hydroxychloroquine at 384 nm and 394 nm, respectively without interference from favipiravir. Different factors affecting the spectrofluorometric measurement process have been verified. The drugs under the study have been successfully quantitatively analyzed in the spiked plasma using the proposed method.

Analytical Performance and Greenness Evaluation of Five Multi-Level Design Models Utilized for Impurity Profiling of Favipiravir, a Promising COVID-19 Antiviral Drug

In 2018, the discovery of carcinogenic nitrosamine process related impurities (PRIs) in a group of widely used drugs led to the recall and complete withdrawal of several medications that were consumed for a long time, unaware of the presence of these genotoxic PRIs. Since then, PRIs that arise during the manufacturing process of the active pharmaceutical ingredients (APIs), together with their degradation impurities, have gained the attention of analytical chemistry researchers. In 2020, favipiravir (FVR) was found to have an effective antiviral activity against the SARS-COVID-19 virus. Therefore, it was included in the COVID-19 treatment protocols and was consequently globally manufactured at large-scales during the pandemic. There is information indigence about FVR impurity profiling, and until now, no method has been reported for the simultaneous determination of FVR together with its PRIs. In this study, five advanced multi-level design models were developed and validated for the simultaneous determination of FVR and two PRIs, namely; (6-chloro-3-hydroxypyrazine-2-carboxamide) and (3,6-dichloro-pyrazine-2-carbonitrile). The five developed models were classical least square (CLS), principal component regression (PCR), partial least squares (PLS), genetic algorithm-partial least squares (GA-PLS), and artificial neural networks (ANN). Five concentration levels of each compound, chosen according to the linearity range of the target analytes, were used to construct a five-level, three-factor chemometric design, giving rise to twenty-five mixtures. The models resolved the strong spectral overlap in the UV-spectra of the FVR and its PRIs. The PCR and PLS models exhibited the best performances, while PLS proved the highest sensitivity relative to the other models.