Evaluation of a rapid method for the simultaneous quantification of ribavirin, sofosbuvir and its metabolite in rat plasma by UPLC-MS/MS

A new fluorescence probe for sofosbuvir analysis in dosage form and spiked human plasma

A simple, rapid, and low-cost technique was developed to allow reliable analysis of the anti-hepatitis C drug sofosbuvir in bulk, tablet form, and spiked human plasma. This method depends on the ability of sofosbuvir to quench the fluorescence of the newly synthesized 2-amino-3-cyano-4,6-dimethylpyridine (reagent 3). Elemental analysis and spectral data were used to validate the structure of the synthesized reagent. The newly synthesized reagent exhibited a satisfactory level of fluorescence emission at 365 nm after excitation at 247 nm. All experimental variables that might affect the quenching process were analyzed and optimized. Linearity, range, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ) were all validated in accordance with the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines. The concentration range was shown to be linear between 0.1 and 1.5 μg/mL. The technique was effectively utilized for sofosbuvir analysis in both its tablet dosage form and spiked human plasma, with mean percentage recoveries of 100.13 ± 0.35 and 94.26 ± 1.69, respectively.

Determination of ribavirin by molecularly imprinted electrochemical sensors using pyrro-1-propionyl-alaninoyl-chitooligosaccharide and pyrrole as bifunctional monomers on Prussian blue-gold nanocomposite films

Herein, we developed a highly sensitive imprinted electrochemical sensor for the trace detection of ribavirin (RBV) using pyrrole (PYR) and pyrro-1-propionyl-alaninoyl-chitooligosaccharides (PPACO) as bifunctional monomers on Prussian blue-gold nanocomposite films. PPACO had strong molecular effect on RBV molecule and was selected by quantitative calculations. After the deposition of the Prussian blue-gold nanocomposite on a glassy carbon electrode (GCE) surface, a 4-aminothiophenol layer successfully self-assembled on the surface. Subsequently, the molecularly imprinted membrane (MIM) was subjected to electrochemical polymerization on the electrode surface using RBV as the template and PPACO and PYR as the two monomers. After eluting the RBV molecules from the MIM, the fabricated RBV-MIM/Fn-Au-PB/GCE exhibited the specific adsorption of RBV. Under optimal conditions, differential pulse voltammetry (DPV) was used to measure the performance of the synthesized sensor, which exhibited a linear relationship between the decreasing peak current and RBV concentration from 0.015 to 3.5 μM with a low detection limit of 3 nM (S/N = 3). As a proof of concept, RBV-MIM/Fn-Au-PB/GCE was also applied to monitor the RBV content in RBV granules. It showed a satisfactory recovery (96.5-99.2%) with a relative standard deviation of less than 3.5% (n = 5), and thus, we believe it has potential for practical applications.

Development and validation of LC-MS/MS methods for the simultaneous quantification of sofosbuvir and its major metabolite (GS-331007) in blood plasma and cerebrospinal and seminal fluid: Application to a pilot clinical trial with a focus on Zika

Zika still poses a threat to global health owing to its association with serious neurological conditions and the absence of a vaccine and treatment. Sofosbuvir, an anti-hepatitis C drug, has shown anti-Zika effects in animal and cell models. Thus, this study aimed to develop and validate novel LC-MS/MS methods for the quantification of sofosbuvir and its major metabolite (GS-331007) in human plasma and cerebrospinal (CSF) and seminal fluid (SF), and apply the methods to a pilot clinical trial. The samples were prepared by liquid-liquid extraction and separated using isocratic mode on Gemini C₁₈ columns. Analytical detection was performed using a triple quadrupole mass spectrometer equipped with an electrospray ionization source. The validated ranges for sofosbuvir were 0.5-2,000 ng/mL (plasma) and 0.5-100 ng/mL (CSF and SF), while for the metabolite they were 2.0-2,000 ng/mL (plasma), 5.0-200 ng/mL (CSF) and 10-1,500 ng/mL (SF). The intra-day and inter-day accuracies (90.8-113.8%) and precisions (1.4-14.8%) were within the acceptance range. The developed methods fulfilled all validation parameters concerning selectivity, matrix effect, carryover, linearity, dilution integrity, precision, accuracy and stability, confirming the suitability of the method for the analysis of clinical samples.

The characterization and quantification of structures of Cajanus scarabaeoides phytochemicals and their seasonal variation analysis using ultra-performance liquid chromatography-tandem mass spectrometry

RATIONALE

Cajanus scarabaeoides, belonging to the Fabaceae family, is an underutilized herb and traditionally used to treat several ailments. However, it is not well explored phytochemically. Therefore, mass spectrometry (MS)-based phytochemical analysis was carried out to investigate the bioactive ingredients of the herb.

METHODS

A ultra-performance liquid chromatography (UPLC) coupled to photodiode array detection (PDA) and electrospray ionization (ESI) tandem mass spectrometry (UPLC-PDA-ESI-MS/MS) system was used for the qualitative and quantitative analysis of phytochemicals. The chromatographic separation was achieved on the Acquity BEH C18 column (150 × 2.1 mm, 1.7 μm) using a gradient system consisting of three solvents, acetonitrile, methanol, and 0.1% formic acid, used at a flow rate of 0.300 ml/min.

RESULTS

Sixteen bioactive ingredients (gallic acid, gallocatechin, epigallocatechin, catechin, procyanidin dimer, epicatechin, procyanidin trimer, isoorientin, orientin, vitexin, isovitexin, quercetin-mono-O-glycoside, isoquercitrin, luteolin-7-O-glucoside, quercetin, and luteolin) were identified and structurally characterized. Consequently, 12 compounds were reported for the first time from C. scarabaeoides, and 13 were quantitatively determined in different seasons. Isoorientin (10.2-7.1% w/w) and orientin (5.78-5.17% w/w) were the most abundant constituents in the dry weight of plant material, followed by vitexin and isovitexin in the rainy season.

CONCLUSIONS

The phytochemical investigation has revealed that C. scarabaeoides could be a potential alternate source of bioactive ingredients, namely, isoorientin, orientin, vitexin, and isovitexin, contributing to further exploration of its biological activity. In addition, analytical methods can be used for the rapid identification and quantification of bioactive ingredients in C. scarabaeoides.

RP-HPLC Method Development, Validation, and Drug Repurposing of Sofosbuvir Pharmaceutical Dosage Form: A Multidimensional Study

A smooth, exceptionally sensitive, correct, and extra reproducible RP-HPLC technique was developed and demonstrated to estimate Sofosbuvir (SOF) in pharmaceutical dosage formulations. This process was carried out by Agilent High-Pressure Liquid Chromatograph 1260 with GI311C Quat. Pump, Phenomenex Luna C-18 (150 mm × 4.6 mm × 5 μm) (USA), and Photodiode Array Detector (PDA) G1315D. The cell section, including acetonitrile and methanol with 80:20 v/v and solution (B) 0.1% phosphoric acid (40:60), was used for the study. However, 10 μL of the sample was injected with a drift flow of 1 mL/min. The separation occurred at a column temperature of 30 °C, and the eluents used PDA set at 260 nm. The retention time of SOF was 5 min. The calibration curve was modified linearly within the range of 0.05-0.15 mg/mL with a correlation coefficient of 0.99 and genuine linear dating among top vicinity and consciousness in the calibration curve. The detection and quantification restrictions were 0.001 and 0.003 mg/mL, respectively. SOF recovery from pharmaceutical components ranged from 98% to 99%. The percentage assay of SOF was 99%. Analytical validation parameters, such as specificity, linearity, precision, accuracy, and selectivity, were studied, and the percentage relative standard deviation (%RSD) was less than 2%. All other key parameters were observed within the desired thresholds. Hence, the proposed RP-HPLC technique was proven effective for developing SOF in bulk and pharmaceutical pill dosage forms. SOF was found to interact with SARS-COV-2 nsp12, and molecular docking results revealed its high affinity and firm binding within the active site groove of nsp12. The key interacting residues include; LYS-72, GLN-75, MET-80 ALA-99, ASN-99, TRP-100, TYR-101 with ASN-99 and TRP-100 forming hydrogen bonds. Molecular Dynamics simulation of SOF and nsp12 complex elucidated that the system was stable throughout 20ns. Therefore, this drug repurposing strategy for SOF can be used for treating COVID-19 infections by performing animal experiments and accurate clinical trials in the future.

Effects of aged garlic and ginkgo biloba extracts on the pharmacokinetics of sofosbuvir in rats

Sofosbuvir is a direct acting antiviral (DAA) approved for the treatment of hepatitis C virus (HCV). Sofosbuvir is a substrate of P-glycoprotein (P-gp). For this reason, inhibitors, or inducers of intestinal P-gp may alter the plasma concentration of sofosbuvir and increase or decrease its efficacy causing a significant change in its pharmacokinetic parameters. The purpose of the study was to evaluate the pharmacokinetic interaction between either aged garlic or ginkgo biloba extracts with sofosbuvir through targeting P-gp as well as possible toxicities in rats. Rats were divided into four groups and treated for 14 days with saline, verapamil (15 mg/kg, PO), aged garlic extract (120 mg/kg, PO), or ginkgo biloba extract (25 mg/kg, PO) followed by a single oral dose of sofosbuvir (40 mg/kg). Validated LC-MS/MS was used to determine sofosbuvir and its metabolite GS-331007 in rat plasma. Aged garlic extract caused a significant decrease of sofosbuvir AUC(0-t) by 36%, while ginkgo biloba extract caused a significant increase of sofosbuvir AUC(0-t) by 11%. Ginkgo biloba extract exhibited a significant increase of the sofosbuvir t1/2 by 60%, while aged garlic extract significantly increased the clearance of sofosbuvir by 63%. The pharmacokinetic parameters of GS-331007 were not affected. The inhibitory action of ginkgo biloba on P-gp and the subsequent increase in the sofosbuvir plasma concentration did not show a significant risk of renal or hepatic toxicity. Conversely, although aged garlic extracts increased intestinal P-gp expression, they did not alter the Cmax and Tmax of sofosbuvir and did not induce significant hepatic or renal toxicities.

Analytical Methods for the Determination of Major Drugs Used for the Treatment of COVID-19. A Review

At the beginning of the COVID-19 outbreak (end 2019 - 2020), therapeutic treatments based on approved drugs have been the fastest approaches to combat the new coronavirus pandemic. Nowadays several vaccines are available. However, the worldwide vaccination program is going to take a long time and its success will depend on the vaccine public's acceptance. Therefore, outside of vaccination, the repurposing of existing antiviral, anti-inflammatory and other types of drugs, have been considered an alternative medical strategy for the COVI-19 infection. Due to the broad clinical potential of the drugs, but also to their possible side effects, analytical methods are needed to monitor the drug concentrations in biological fluids and pharmaceutical products. This review deals with analytical methods developed in the period 2015 - July 2021 to detect potential drugs that, according to a literature survey, have been taken into consideration for the treatment of COVID-19. The drugs considered here have been selected on the basis of the number of articles published in the period January 2020-July 2021, using the combination of the keywords: COVID-19 and drugs or SARS-CoV-2 and drugs. A section is also devoted to monoclonal antibodies. Over the period considered, the analytical methods have been employed in a variety of real samples, such as body fluids (plasma, blood and urine), pharmaceutical products, environmental matrices and food.

Innovative derivative/zero ratio spectrophotometric method for simultaneous determination of sofosbuvir and ledipasvir: Application to average content and uniformity of dosage units

An innovative simple, rapid and sensitive spectrophotometric method was developed for the simultaneous analysis of sofosbuvir (SOF) and ledipasvir (LED) in their combined dosage forms. Sofosbuvir with ledipasvir (SOF/LED) as a combined dosage form was tried at the pandemic COVID 19 crisis. This technique has the advantages of both zero order and first order spectrophotometry. The zero and first derivative amplitudes were measured at 274.2 nm for SOF (zero crossing point of LED in first derivative spectrum) and 314 nm for LED (zero crossing point of SOF in first derivative spectrum) over the concentration range of 2.0-50.0 μg mL^-1 with coefficients of determination (R²) > 0.9999 for both drugs and mean percentage recoveries of 100.25 ± 1.61 and 99.85 ± 0.99 for SOF and LED; respectively. This original method was validated according to ICH requirements and statistically compared to published comparison methods. This method was applied to estimate the average content and the uniformity of dosage units of SOF/LED combined dosage form according to British Pharmacopeia requirements.

Recent advances in the chromatographic determination of the most commonly used anti-hepatitis C drug sofosbuvir and its co-administered drugs in human plasma

Sofosbuvir is a direct-acting antiviral drug that inhibits hepatitis C virus (HCV) NS5B polymerase, which in turn affects the virus replication inside biological systems. The clinical importance of sofosbuvir is based not only on its effect on HCV but also on other lethal viruses such as Zika and severe acute respiratory syndrome coronavirus disease 2019 (SARS-COVID-19). Accordingly, there is a continuous shedding of light on the development and validation of accurate and fast analytical methods for the determination of sofosbuvir in different environments. This work critically reviews the recent advances in chromatographic methods for the analysis of sofosbuvir and/or its metabolites in pure samples, pharmaceutical dosage forms, and in the presence of other co-administered drugs to highlight the current status and future perspectives to enhance its determination in different matrixes.

Feasible TLC-Spectro-Densitometry Technique for Simultaneous Determination of Two Hepatitis C Antiviral Drugs, Sofosbuvir and Simeprevir: Application to Combined Pharmaceutical Dosage Forms and Human Plasma

A high-performance thin-layer chromatographic method was developed and validated for the concurrent determination of simeprevir (SMV) and sofosbuvir (SOF). The chromatographic separation was attained on silica gel 60 F254 as stationary phase and ethyl acetate-hexane-methanol (5.0:4.0:1.0, v/v/v) as developing solvent with UV detection at 273 nm. The RF values were 0.67±0.02 and 0.43±0.02 for SMV and SOF, respectively. The method has been validated in respect to the guidelines of the International Conference on Harmonization. Linearity was maintained between 60-1,000 and 70-1,200 ng/band for SMV and SOF, respectively, with good correlation coefficients (0.9993-0.9997) for both drugs. The suggested method was highly sensitive as the calculated detection limits were 15 and 22 ng/band, while the quantitation limits were 44 and 66 ng/ band for SMV and SOF, respectively. The suggested methodology has been effectively employed for the determination of the mentioned drugs in their pure forms and their pharmaceutical dosage forms as well as human plasma without significant interference of the pharmaceutical excipients or plasma components.

Detection and quantification of Covid-19 antiviral drugs in biological fluids and tissues

Since coronavirus disease 2019 (COVID-19) started as a fast-spreading pandemic, causing a huge number of deaths worldwide, several therapeutic options have been tested to counteract or reduce the clinical symptoms of patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific drugs for COVID-19 are available, but many antiviral agents have been authorised by several national agencies. Most of them are under investigation in both preclinical and clinical trials; however, pharmacokinetic and metabolism studies are needed to identify the most suitable dose to achieve the desired effect on SARS-CoV-2. Therefore, the efforts of the scientific community have focused on the screening of therapies able to counteract the most severe effects of the infection, as well as on the search of sensitive and selective analytical methods for drug detection in biological matrices, both fluids and tissues. In the last decade, many analytical methods have been proposed for the detection and quantification of antiviral compounds currently being tested for COVID-19 treatment. In this review, a critical discussion on the overall analytical procedure is provided, i.e (a) sample pre-treatment and extraction methods such as protein precipitation (PP), solid-phase extraction (SPE), liquid-liquid extraction (LLE), ultrasound-assisted extraction (UAE) and QuEChERS (quick, easy, cheap, effective, rugged and safe), (b) detection and quantification methods such as potentiometry, spectrofluorimetry and mass spectrometry (MS) as well as (c) methods including a preliminary separation step, such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) coupled to UV-Vis or MS detection. Further current trends, advantages and disadvantages and prospects of these methods have been discussed, to help the analytical advances in reducing the harm caused by the SARS-CoV-2 virus.

Tandem mass spectrometry of small-molecule antiviral drugs: 3. antiviral agents against herpes, influenza and other viral infections

For the treatment of various viral infections, antiviral drugs may be used. Liquid chromatography-mass spectrometry (LC-MS) with tandem mass spectrometry (MS-MS) operated in selected-reaction monitoring (SRM) mode is the method of choice in quantitative bioanalysis of drugs, e.g., to establish bioavailability, to study pharmacokinetics, and later on possibly for therapeutic drug monitoring. In this study, the fragmentation in MS-MS of small-molecule antiviral drugs against herpes and influenza viruses is reviewed. In this way, insight is gained on the identity of the product ions used in SRM. Fragmentation schemes of antiviral agents are also relevant in the identification of drug metabolites or (forced) degradation products. As information of the fragmentation of antiviral drugs in MS-MS and the identity of the product ions is very much scattered in the scientific literature, it was decided to collect this information and to review it. In this third study, attention is paid to small-molecule antiviral agents used against herpes and influenza virus infections. In addition, some attention is paid to broad-spectrum antiviral agents, that are investigated with respect to their efficacy in challenging virus infections of this century, e.g., involving Ebola, Zika and corona viruses, like SARS-CoV-2, which is causing a world-wide pandemic at this very moment. The review provides fragmentation schemes of ca. 35 antiviral agents. The identity of the product ions used in SRM, i.e., elemental composition and exact-m/z, is tabulated, and more detailed fragmentation schemes are provided.

Micellar high performance liquid chromatographic method for separation and validation of two anti-hepatitis C- virus drugs in pure form, human plasma and human urine

OBJECTIVES

In the present study, an eco- friendly micellar liquid chromatographic technique was validated for separation and quantification of two drugs; namely ribavirin (RIV), and sofosbuvir (SBV) in pure form, pharmaceuticals containing them, human plasma and human urine. These drugs are administered co-administered for treatment of Hepatitis C virus (HCV) that causes hepatitis C in humans.

MATERIAL AND METHODS

These drugs were separated using Nucleosil 100-5 phenyl column. Sodium dodecyl sulphate (SDS) solution (0.05M, pH 7.0) containing triethylamine (0.3%) and n-butanol (10%) was used as a mobile phase with 1.2 mLmin^-1 flow rate and 215nm detection wavelength. Nine minutes were required for resolving the two drugs from the matrix.

RESULTS

The method showed good linearity for RIV and SBV with correlation coefficients (r²) more than 0.9996 within the concentration ranges of (20-400) and (40-400) ngmL^-1 in pure form, (30-300) and (50-300) ngmL^-1 in human plasma and (20-400) and (40-400) ngmL^-1 in human urine, respectively.

CONCLUSION

The recommended method was applied for examination of RIV and SBV in pure and pharmaceuticals. The obtained results were statistically matched with reported methods with no significant differences. Also, the recommended method was effectively applied for estimation of both drugs in spiked human urine and plasma without purification or extraction steps and real samples of plasma and urine of humans having therapy of RIV and SBV, as well as, performing tablets dissolution-rate tests with satisfactory results.

Chemometrically Assisted Development of Ultra-High-Performance Liquid Chromatography Method for the Simultaneous Quantification of Sofosbuvir, Daclatasvir and Ledipasvir in Pharmaceutical Dosage Forms

A new ultra-high-performance liquid chromatography method for the simultaneous quantification of sofosbuvir, daclatasvir and ledipasvir was developed. Two combinations of these direct-acting antivirals are used in hepatitis C virus infection therapy and show high efficacy and safety. Fractional factorial design was used for screening the most influential factors on separation and time analysis. These significant factors were optimized using a central composite design. The optimum resolution was carried out by using a Waters XBridge C18 column (150 mm, 4.6 mm ID, 5 μm) at a temperature of 35°C ± 2°C and acetonitrile/sodium perchlorate buffer (10 mM, pH = 3.2) (40: 60 v/v) as mobile phase at a flow rate of 1.5 mL min-1. UV detection was set at λ = 210 nm. A short chromatographic separation time was achieved. The developed method was validated according to the accuracy profile approach and was found specific, precise, faithful and accurate. The detection limits were between 0.07 and 0.13 μg mL-1. Hence, this novel method can be employed for the routine quality control analysis and in dissolution profile studies of generics containing these products.

Two novel UPLC methods utilizing two different analytical columns and different detection approaches for the simultaneous analysis of velpatasvir and sofosbuvir: application to their co-formulated tablet

In the present study two different RSLC columns, Acclaim RSLC 120 C18, 5.0 µm, 4.6 × 150 mm (column A) and Acclaim RSLC 120 C18, 2.2 µm, 2.1 × 100 mm (Column B) were utilized for the analysis of velpatasvir (VPS) in presence of sofosbuvir (SFV), where due to the encountered fluorescent properties of VPS fluorescent detection at 405 nm after excitation at 340 nm (Method 1) was used for its detection where the non-fluorescent SFV did not interfere. The same columns were further utilized for the simultaneous determination of SFV and VPS either in bulk form or in their combined tablet, where UV- spectrophotometric detection at 260 nm was selected for the simultaneous analysis of both drugs (Method 2). A mobile phase consisting of NaH2PO4, pH 2.5 (with phosphoric acid) and acetonitrile in a ratio of 60:40 v/v was used for both methods. The mobile phase was pumped at a flow rate of 1.0 mL/min when using column, A and 0.5 mL/min when using column B. The methods showed good linearity over the concentration ranges of 1.0-5.0 and 2.5-10.0 ng/mL for VPS when utilizing Method 1 A and B respectively. Where the linearity concentration range was from 30.0-150.0 to 120-600.0 ng/mL for VPS and SFV respectively when applying Method 2. Both methods 1 and 2 were performed by utilizing the two analytical columns. The different chromatographic parameters as retention time, resolution, number of theoretical plates (N), capacity factor, tailing factor and selectivity were carefully optimized. The results show that comparing the performance of the two utilized columns revealed that shorter column (2.1 mm × 100 mm) with small particle packing was superior to the longer column (4.6 × 150 mm) for the analysis of the studied drugs allowing a reduction of the analysis time by 70% without any detrimental effect on performance. This prompts the decrease of the investigation costs by saving money on organic solvents and expanding the overall number of analyses per day.

Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) in practice: analysis of drugs and pharmaceutical formulations

Background

UHPLC-MS/MS is connected in various research facilities for the qualitative and quantitative investigation of a pharmaceutical substance, pharmaceutical items, and biological specimen.

Main body

The commence review article is an endeavor to offer pervasive awareness around assorted aspects and details about the UHPLC-MS/MS and related techniques with the aim on practice to an estimation of medicinal active agents in the last 10 years. The article also focused on isolation, separation, and characterization of present impurity in drug and biological samples.

Conclusion

Review article compiles a general overview of medicinally important drugs and their analysis with UHPLC-MS/MS. It gives fundamental thought regarding applications of UHPLC-MS/MS for the study on safety limit. The summary of developed UHPLC-MS/MS methods gives a contribution to the future trend and limitations in this area of research.

A Novel Simultaneous Estimation of Sofosbuvir and Velpatasvir in Human Plasma by Liquid Chromatography Tandem-Mass Spectrometry after Protein Precipitation Method

Objective:

The aim of the present work is to achieve a novel highly sensitive chromatographic method for the simultaneous determination of hepatitis C agents, sofosbuvir and velpatasvir from human plasma using ritonavir as an internal standard.

Methods:

Chromatographic separation was achieved using Hypersil C18 column (50mm x 4.6mm, 3μm) with an isocratic elution mode using the mobile phase composition 10 mM ammonium formate buffer (pH 5.0): acetonitrile (20:80 v/v) pumped at a flow rate of 0.5 ml/min. The detection was carried out by tandem mass spectrometry using Multiple Reaction Monitoring (MRM) positive Electrospray Ionization (ESI) with proton adducts at m/z 530.10 > 243.10, 883.40 > 114.0 and 721.25 > 197.0.

Results:

The method validated as per USFDA guidelines with respect to linearity, accuracy, and precision was found to be acceptable over the concentration range of 0.2–2000 ng/ml and 5-2000 ng/ml for sofosbuvir and velpatasvir respectively and the method was found to be highly sensitive and selective.

Conclusion:

The developed tandem mass spectrometric method is robust and can be applied for the monitoring of plasma levels of the analyzed drug in preclinical and clinical pharmacokinetic studies.

Validated RP-HPLC Method for Simultaneous Determination of Ribavirin, Sofosbuvir and Daclatasvir in Human Plasma: A Treatment Protocol Administered to HCV Patients in Egypt

Egypt has the highest prevalence of hepatitis C virus (HCV) in the world thus it launched a national program for eliminating HCV aiming to treat 300,000 HCV patients per year. Three anti-HCV co-administered drugs; ribavirin (RBV), sofosbuvir (SF) daclatasvir (DAC) were simultaneously determined in human plasma by a validated, simple and sensitive RP-HPLC method using propyl paraben as an internal standard. Liquid-liquid extraction using ethyl acetate was used for samples extraction. Chromatographic separation was achieved on Scharlau® C18 column (250 × 4.6 mm2, 5 μm). Gradient elution was employed with a mobile phase mixture of water and acetonitrile at a flow rate 1 mL/min. UV detection using photodiode array detector was carried out at 207, 260 and 312 nm for RBV, SF and DAC, respectively. Method validation was performed according to the FDA guidelines for bioanalytical method validation. The calibration curves were linear over the ranges (0.5-80, 0.1-40 and 0.5-80 μg/mL) with average recoveries (100.64-108.28%, 98.48-105.91% and 97.68-101.38%) for RBV, SF and DAC, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limits. Stability assays revealed that the three studied analytes were stable during sample storage, preparation and injection. The method can be successfully applied in routine analysis of plasma of HCV patients treated with this combination therapy which aids in therapeutic drug monitoring and patients' follow-up especially in Egypt and other developing countries fighting HCV.

Modification of N,S co-doped graphene quantum dots with p-aminothiophenol-functionalized gold nanoparticles for molecular imprint-based voltammetric determination of the antiviral drug sofosbuvir

A molecularly imprinted polymer (MIP) was developed for the electrochemical determination of the antiviral drug sofosbuvir (SOF). The MIP was obtained by polymerization of p-aminothiophenol (p-ATP) on N,S co-doped graphene quantum dots (N,S@GQDs) in the presence of gold nanoparticles to form gold-sulfur covalent network. The presence of quantum dots improves the electron transfer rate, enhances surface activity and amplifies the signal. The nanocomposites were characterized by FTIR, TEM, EDX, and SEM. The electrochemical performance of the electrode was investigated by differential pulse voltammetry and cyclic voltammetry. The sensor uses hexacyanoferrate as the redox probe and is best operated at a potential of around 0.36 V vs. Ag/AgCl. It has a linear response over the concentration range of 1-400 nM SOF, with a detection limit of 0.36 nM. Other features include high selectivity, good reproducibility and temporal stability. The sensor was applied to the determination of SOF in spiked human plasma. Graphical abstract Novel sofosbuvir imprinted p-ATP polymer was synthesized by the aid of gold nanoparticles on N,S co-doped graphene quantum dots as a good conductive support. The imprinted polymer was used for detection of sofosbuvir in real samples by using the ferri/ferrocyanide redox probe.

Recent Advances on Drug Analyses Using Ultra Performance Liquid Chromatographic Techniques and their Application to the Biological Samples

Introduction:

Ultra-Performance Liquid Chromatographic (UPLC) method enables analyst to establish an analysis at higher pressure than High Performance Liquid Chromatographic (HPLC) method towards liquid chromatographic methods. UPLC method provides the opportunity to study a higher pressure compared to HPLC, and therefore smaller column in terms of particle size and internal diameter are generally used in drug analysis. The UPLC method has attracted gradually due to its advantages such as short analysis time, the small amount of waste reagents and the significant savings in the cost of their destruction process. In this review, the recent selected studies related to the UPLC method and its method validation are summarized. The drug analyses and the results of the studies which were investigated by UPLC method, with certain parameters from literature are presented.

Background:

Quantitative determination of drug active substances by High-Performance Liquid Chromatography (HPLC) from Liquid Chromatography (LC) methods has been carried out since the 1970's with the use of standard analytical LC methods. In today's conditions, rapid and very fast even ultra-fast, flow rates are achieved compared to conventional HPLC due to shortening analysis times, increasing method efficiency and resolution, reducing sample volume (and hence injection volume), reducing waste mobile phase. Using smaller particles, the speed and peak capacity are expanding to new limit and this technology is named as Ultra Performance Liquid Chromatography. In recent years, as a general trend in liquid chromatography, ultra-performance liquid chromatography has taken the place of HPLC methods. The time of analysis was for several minutes, now with a total analysis time of around 1-2 minutes. The benefits of transferring HPLC to UPLC are much better understood when considering the thousands of analyzes performed for each active substance, in order to reduce the cost of analytical laboratories where relevant analysis of drug active substances are performed without lowering the cost of research and development activities.

Methods:

The German Chemist Friedrich Ferdinand Runge, proposed the use of reactive impregnated filter paper for the identification of dyestuffs in 1855 and at that time the first chromatographic method in which a liquid mobile phase was used, was reviewed. Christian Friedrich Chönbein, who reported that the substances were dragged at different speeds in the filter paper due to capillary effect, was followed by the Russian botanist Mikhail S. Tswet, who planted studies on color pigment in 1906. Tswet observes the color separations of many plant pigments, such as chlorophyll and xanthophyll when he passes the plant pigment extract isolated from plant through the powder CaCO3 that he filled in the glass column. This method based on color separation gives the name of "chromatographie" chromatography by using the words "chroma" meaning "Latin" and "graphein" meaning writing.

Results and Conclusion:

Because the UPLC method can be run smoothly at higher pressures than the HPLC method, it offers the possibility of analyzing using much smaller column sizes and column diameters. Moreover, UPLC method has advantages, such as short analysis time, the small amount of waste reagents and the significant savings in the cost of their destruction process. The use of the UPLC method especially analyses in biological samples such as human plasma, brain sample, rat plasma, etc. increasingly time-consuming due to the fact that the analysis time is very short compared to the HPLC, because of the small amount of waste analytes and the considerable savings in their cost.

Novel spectrophotometric and factor-based multivariate calibration-prediction techniques for determination of two inhibitors of hepatitis C-virus and hepatocellular carcinoma in pure, human urine, and human plasma

Novel univariate and multivariate factor-based calibration-prediction techniques were validated for simultaneous ultraviolet spectrophotometric determination of ribavirin (RIV), daclatasvir (DAV), sofosbuvir (SOV), and sorafenib (SON) which are co-administered for treatment of hepatocellular carcinoma (HCC) that results from Hepatitis C-virus (HCV) infection in their commercial products and in biological fluids. Determination of these compounds is essential owing to their pharmacotherapeutic benefits. Due to spectral overlapping of RIV, DAV, SOV, and SON, univariate extended derivative ratio (EDR) method and multivariate partial least-squares (PLS) and principal component regression (PCR) methods were used for constructing the calibration curves. The extended derivative ratio (EDR) absorption maxima at 215 nm and minima at 310.5 nm was used for determination of RIV and DAV, respectively and absorption maxima at 240.3 nm and minima at 284.5 nm for determination of SOV and SON, respectively. The linearity was established over the range of 6-42 μg mL^-1, 4-16 μg mL^-1, 10-70 μg mL^-1, and 3-9 μg mL^-1 for RIV, DAV, SOV and SON with correlation coefficient (r2) of 0.9997, 0.9997, 0.9999 and 0.9997, respectively. This method was effectively applied to pure, pharmaceutical preparations and to spiked human urine and plasma. PLS and PCR models were established for the determination of the studied drugs in the range of 6-42, 4-16, 10-70 and 3-9 μg mL^-1 for RIV, DAV, SOV, and SON, respectively. Furthermore, updating the PLS model (PLS model update) were allowed for the determination of these drugs in spiked human urine, plasma and drug-dissolution test of their tablets. The obtained results were compared to official and reported method showing that there were no significant differences. The results of applying PLS and PCR models for evaluation of RIV, DAV, SOV, and SON in human urine samples as real samples were also encouraging. It is expected that the suitable features of the proposed method make it helpful for biological and clinical applications.

Quick and Sensitive UPLC-ESI-MS/MS Method for Simultaneous Estimation of Sofosbuvir and Its Metabolite in Human Plasma

A simple, fast and highly sensitive RP-UPLC-MS/MS method was developed and validated for the simultaneous determination of sofosbuvir (SR) and its metabolite GS331007 in human plasma using ketotifen as an internal standard (IS). The separation was achieved on Acquity UPLC BEH C₁₈ (50 × 2.1 mm, i.d. 1.7 µm, Waters, USA) column using acetonitrile:5 mM ammonium formate:0.1% formic acid (85:15:0.1% v/v/v) as a mobile phase at a flow rate of 0.35 mL/min in an isocratic elution. The Xevo TQD UPLC-MS/MS was operated under the multiple-reaction monitoring mode using positive electrospray ionization. Extraction with dichloromethane was used in the sample preparation. Method validation was performed as per the Food and Drug Administration (FDA) guidelines and the calibration curves of the proposed method were found to be linear in the range of 1–1000 ng/mL for SR and in the range of 10–1500 ng/mL for its metabolite (GS331007) with an elution time of 1.83 min. All validation parameters were within the acceptable range according to the bioanalytical methods validation guidelines. Furthermore, the obtained results of matrix effects indicate that ion suppression or enhancement from human plasma components was negligible under the optimized conditions. The proposed method can be applied in high-throughput analysis required for pharmacokinetic and bioequivalence studies in human samples.

Earth-friendly spectrophotometric methods for simultaneous determination of ledipasvir and sofosbuvir: Application to average content and uniformity of dosage unit testing

Simple, rapid, sensitive, accurate, precise and earth-friendly spectrophotometric methods were developed for the simultaneous analysis of ledipasvir (LED) and sofosbuvir (SOF) without interference of both sunset yellow dye and copovidone excipients (the most probable interferents) in their combined dosage form. These proposed methods were based on measurement of LED in synthetic mixtures and combined dosage form by first derivative (¹D) spectrophotometry at 314 nm over the concentration range of 2-50 μg mL^-1 with coefficient of determination (R²) > 0.9999, mean percentage recovery of 99.98 ± 0.62. On the other hand, SOF in synthetic mixtures and combined dosage form was determined by five methods. Method I is based on the use of ¹D spectrophotometry at 274.2 nm (zero crossing point of LED). Method II involves the application of conventional dual wavelength method (DW) at the absolute difference between SOF zero order amplitudes at 261 nm (λ_max of SOF) and 364.7 nm. At these wavelengths, the absolute difference between LED zero order amplitudes was observed to equal zero. Method III depends on isosbestic point method (ISP) in which the total concentration of both drugs was measured at isosbestic point at 262.7 nm. Concentration of SOF could be obtained by subtraction of LED concentration. While, method IV depends on absorbance correction method (absorption factor method), which is based on determination of SOF concentration at 262.7 nm (λ_ISP) and LED at 333 nm (λ_max of LED). Finally, method V depends on absorbance ratio method (Q-analysis) in which 262.7 nm (λ_ISP) and 261 nm (λ_max of SOF) were selected to determine SOF concentration. The linearity range for all methods for SOF determination was 2-50 μg mL^-1 with coefficient of determination (R²) > 0.9999. Methods I, II & III were also applied for determination of SOF concentration in single dosage form. Their mean percentage recoveries were 100.35 ± 1.85, 99.97 ± 0.54 and 100.03 ± 0.49, for the three methods respectively. The proposed methods were validated according to international conference of harmonization (ICH) requirements and statistically compared to published reference methods. The ANOVA test confirmed that there is no significant differences between the proposed methods, and can be used for routine analysis of LED and SOF in commercial tablets. These developed methods were applied to estimate the average content and uniformity of dosage unit for LED/SOF combined dosage form and SOF single dosage form according to British pharmacopeia (BP) requirements.

Comparative study of six sequential spectrophotometric methods for quantification and separation of ribavirin, sofosbuvir and daclatasvir: An application on Laboratory prepared mixture, pharmaceutical preparations, spiked human urine, spiked human plasma, and dissolution test

In accordance with International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines, six novel, simple and precise sequential spectrophotometric methods were developed and validated for the simultaneous analysis of Ribavirin (RIB), Sofosbuvir (SOF), and Daclatasvir (DAC) in their mixture without prior separation steps. These drugs are described as co-administered for treatment of Hepatitis C virus (HCV). HCV is the cause of hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma) and lymphomas in humans. These techniques consisted of several sequential steps using zero, ratio and/or derivative spectra. DAC was first determined through direct spectrophotometry at 313.7 nm without any interference of the other two drugs while RIB and SOF can be determined after ratio subtraction through five methods; Ratio difference spectrophotometric method, successive derivative ratio method, constant center, isoabsorptive method at 238.8 nm, and mean centering of the ratio spectra (MCR) at 224 nm and 258 nm for RIB and SOF, respectively. The calibration curve is linear over the concentration ranges of (6-42), (10-70) and (4-16) μg/mL for RIB, SOF, and DAC, respectively. This method was successfully applied to commercial pharmaceutical preparation of the drugs, spiked human urine, and spiked human plasma. The above methods are very simple methods that were developed for the simultaneous determination of binary and ternary mixtures and so enhance signal-to-noise ratio. The method has been successfully applied to the simultaneous analysis of RIB, SOF, and DAC in laboratory prepared mixtures. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Simultaneous quantitation of two direct acting hepatitis C antivirals (sofosbuvir and daclatasvir) by an HPLC-UV method designated for their pharmacokinetic study in rabbits

Sofosbuvir (SOF) and daclatasvir (DCS) are novel, recently developed direct acting antiviral agents characterized by potent anti-hepatitis C virus action. A fast and efficient HPLC-UV method was developed, validated and applied for simultaneous determination of SOF and DCS in pharmaceutical formulations and biological fluids based on coupling liquid-liquid extraction with ultrasound and dual wavelength detection at λ_max; 260 and 313 nm for SOF and DCS, respectively. This approach provided simple, sensitive, specific and cost-effective determination of the SOF-DCS mixture with good recoveries of the analytes from plasma. Analytes were separated within 7 min on C₁₈ analytical column with acetonitrile-10 mM acetate buffer of pH 5.0 at a flow rate of 1.0 mL min^-1. The linear ranges were 1-20 μg mL^-1 for SOF and 0.6-6 μg mL^-1 for DCS with correlation coefficients ≥0.9995. The detection limits in spiked rabbit plasma were 0.20 and 0.19 μg mL^-1 for SOF and DCS, respectively. The method was validated according to ICH and US-FDA guidelines. Finally, the method was successfully applied for simultaneous pharmacokinetic studies of SOF and DCS in rabbits using rofecoxib as internal standard.

Comparison between core-shell and totally porous particle stationary phases for fast and green LC determination of five hepatitis-C antiviral drugs

The performances of core-shell 2.7 μm and fully porous sub-2 μm particles packed in narrow diameter columns were compared under the same chromatographic conditions. The stationary phases were compared for fast separation and determination of five new antiviral drugs; daclatasvir, sofosbuvir, velpatasvir, simeprevir, and ledipasvir. The gradient elution was done using ethanol as green organic modifier, which is more environmentally friendly. Although both columns provided very good resolution of the five drugs, core-shell particles had proven to be of better efficiency. Under gradient elution conditions, core-shell particles exhibited faster elution, better peak shape, and enhanced resolution adding to lower system backpressure. The column backpressure on sub-2 μm particles was more than twice that on core-shell particles. This gives a chance to use conventional high-performance liquid chromatography conditions without needing special instrumentation as that required for ultra-high performance liquid chromatography. The method was validated for determination of the five drugs by gradient elution using mobile phase composed of organic modifier ethanol and aqueous part containing 0.75 g sodium octane sufonate and 3.0 g sodium dihydrogen phosphate per liter at pH of 6.15. Detection was done using UV-detector set at 210 nm. The linearity, accuracy, and precision were found very good within the concentration range of 2-200 μg/mL.

Development and validation of LC-MS/MS method for simultaneous determination of sofosbuvir and daclatasvir in human Plasma: Application to pharmacokinetic study

A simple and highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) bioanalytical method was developed and fully validated for the first time for the simultaneous determination of newly discovered antiviral drugs, namely sofosbuvir (SOF) and daclatasvir (DAC) in human plasma. Tadalafil (TAD) was used as internal standard (IS). SOF, DAC and TAD (IS) were extracted from plasma using liquid-liquid extraction technique with methyl tert-butyl ether. The chromatographic separation was carried out using ZorbaxSB-C₁₈ column (4.6 × 50 mm,5 μm) and 5 mm ammonium formate buffer (pH 3.5)-acetonitrile (50:50, v/v) as mobile phase in an isocratic elution mode pumped at a flow rate 0.7 mL min^-1 . The quantitation was performed on API4500 triple quadrupole tandem mass spectrometer with positive electrospray ionization interface in multiple reaction monitoring mode. Validation was applied according to US Food and Drug Administration guidelines for bio-analytical methodswith respect to linearity, precision, accuracy, selectivity, carry-over, stability and dilution integrity. Linearity was obtained over concentration ranges of 0.3-3000 and 3-3000 ng mL^-1 for SOF and DAC, respectively, by applying a weighted least-squares linear regression method (1/x² ). The proposed method could be applied successfully in bioequivalence and/or clinical studies for therapeutic drug monitoring of patients undergoing dual combination therapy as the latter combination proved more efficacious and powerful tool for the complete treatment of hepatitis C genotype 3 within 16 weeks. The suggested method has been applied successfully to pharmacokinetic studies with excellent assay ruggedness and reproducibility.

UPLC-MS/MS method for the simultaneous quantification of sofosbuvir, sofosbuvir metabolite (GS-331007) and daclatasvir in plasma of HIV/HCV co-infected patients

Direct-acting antiviral agents (DAAs) represent the major advance in hepatitis C virus (HCV) infection treatment leading to extremely high eradication rates in HCV mono- and HIV/HCV co-infected patients. In this scenery, availability of Therapeutic Drug Monitoring (TDM) is of interest to assess plasma concentrations to prevent either therapeutic failure due to suboptimal medication adherence and drug-drug interactions or avoid adverse events. Aim of this study was to develop and validate an Ultra-Performance Liquid Chromatography Mass Spectrometry (UPLC-MS/MS) method for the simultaneous quantification of sofosbuvir, sofosbuvir metabolite (GS-331007), and daclatasvir in human plasma. A simple protein precipitation was applied by adding 200 μL acetonitrile with internal standard 6,7-Dimethyl- 2,3-di(2-pyridyl) quinoxaline to 100 μL plasma sample. Drug separation was performed on analytical C-18 Luna Omega column (50 mm × 2.1 mm I.D.) with particle size of 1.6 μm. The mobile phase consisting of water containing 0.1% formic acid and acetonitrile at flow 0.4 mL/min and a gradient run time of 3.5 min. The injection volume was 10 μL. Anti-HCV drugs were detected in positive electrospray ionization mode. The full scan mass spectral analyses of sofosbuvir, GS-331007, daclatasvir and quinaxoline showed protonated molecule ions and transitions m/z: 530.098 → 243.02, 260.93 → 112.94, 739.4 → 339.27 and 313.03 → 77.99 respectively. The linearity of standard curves was excellent (r² > 0.99), the absolute recovery of anti-HCV drugs ranged between 95 and 98%, and both imprecision and inaccuracy were <15% according to FDA guidelines. The UPLC-MS/MS method was applied to 16 plasma samples of as many HIV/HCV co-infected patients treated with sofosbuvir and daclatasvir. While sofosbuvir was not detectable in all samples, the median plasma concentrations of daclatasvir and GS-331007 were 223.6 ± 319.56 ng/mL and 537.11 ± 242.09 ng/mL, respectively. In conclusion, we describe an UPLC-MS/MS method allowing the simultaneous quantification of sofosbuvir, GS-331007 and daclatasvir in plasma samples. The method was sensitive, specific, robust, and time-saving.

Development and validation of a new HPLC-DAD method for quantification of sofosbuvir in human serum and its comparison with LC-MS/MS technique: Application to a bioequivalence study

Although for many analyses tandem mass spectrometry (LC-MS/MS) systems have significant advantage over the high-performance liquid chromatography with diode array detection (HPLC-DAD) however, the HPLC methods are easier, cheaper and more available to perform. As no published method is available for quantitative HPLC analysis of sofosbuvir (SOF), an orally administered anti-hepatitis drug in human serum, this study was aimed to evaluate applicability of the HPLC technique to quantify sofosbuvir and comparison of the two methods for analytical performance. Following extraction of the drug and an internal standard (Hexobarbital), same chromatographic conditions were used for both the systems. After the chromatographic separation on a reverse phase C18 column using a mobile phase consisting of water (containing formic acid 0.5mL/L) and acetonitrile (57:43; v/v) at a flow rate of 0.8mL/min, the eluate was introduced into a DAD detector set at 261nm, then passed through the mass spectrometry system in single ion monitoring mode (SIM). For UV and mass spectrometry detections the calibration curves were linear over a concentration range of 25-3200 and 10-3200ng/mL, respectively and the linearity was over 0.998 for both the systems. Lower limit of quantification (LLOQ) for mass spectrometry and DAD detections were 10 and 25ng/mL, respectively. In conclusion sensitivity of DAD detection is sufficient enough to determine concentrations down to 0.5% of C_max which achieved in bioequivalence study of sofosbuvir and meet FDA requirements for these types of studies.

Potential of RP-UHPLC-DAD-MS for the qualitative and quantitative analysis of sofosbuvir in film coated tablets and profiling degradants

Sofosbuvir is one of the new direct-acting antiviral drugs against hepatitis C virus (HCV) infection. This drug has recently been launched into the market, and generic versions of the medication are expected to be produced by local drug producers in some countries. Therefore, new methods are required to control sofosbuvir in pharmaceuticals. In the present study, a new method based on reversed phase (RP)-ultra-high performance liquid chromatography (UHPLC) coupled to diode array detection (DAD) and mass spectrometry (MS) was developed to facilitate the qualitative and quantitative analysis of sofosbuvir in film coated tablets. A wavelength of 260 nm was selected to perform a cost-effective quantification and the method showed adequate linearity, with an R2 value of 0.9998, and acceptable values of accuracy (75%-102%) and precision (residual standard deviation <5%). The detection and quantification limits were 0.07 μg/mL and 0.36 μg/mL, respectively. Furthermore, the use of high-resolution MS enabled us to ensure the specificity, check impurities and better sensitivity. Therefore, this methodology promises to be suitable not only for the routine analysis of sofosbuvir in pharmaceutical dosage forms, but also for potential degradants.

Current antiviral drugs and their analysis in biological materials - Part II: Antivirals against hepatitis and HIV viruses

This review is a Part II of the series aiming to provide comprehensive overview of currently used antiviral drugs and to show modern approaches to their analysis. While in the Part I antivirals against herpes viruses and antivirals against respiratory viruses were addressed, this part concerns antivirals against hepatitis viruses (B and C) and human immunodeficiency virus (HIV). Many novel antivirals against hepatitis C virus (HCV) and HIV have been introduced into the clinical practice over the last decade. The recent broadening portfolio of these groups of antivirals is reflected in increasing number of developed analytical methods required to meet the needs of clinical terrain. Part II summarizes the mechanisms of action of antivirals against hepatitis B virus (HBV), HCV, and HIV, their use in clinical practice, and analytical methods for individual classes. It also provides expert opinion on state of art in the field of bioanalysis of these drugs. Analytical methods reflect novelty of these chemical structures and use by far the most current approaches, such as simple and high-throughput sample preparation and fast separation, often by means of UHPLC-MS/MS. Proper method validation based on requirements of bioanalytical guidelines is an inherent part of the developed methods.

Development a validated highly sensitive LC-MS/MS method for simultaneous quantification of Ledipasvir, sofosbuvir and its major metabolite GS-331007 in human plasma: Application to a human pharmacokinetic study

A highly sensitive and rapid LC-MS/MS method was developed, fully optimized and validated for the simultaneous determination of Ledipasvir (LED) and Sofosbuvir (SOF) in the presence of its major metabolite GS-331007 in human plasma using Daclatasvir as internal standard (IS). The extraction of analytes and IS from plasma was performed using liquid-liquid extraction with ethyl acetate. The chromatographic separation of these prepared samples was achieved on Xterra MS C₈ column (4.6×50mm,5μm) using gradient elution with a mobile phase of ammonium formate buffer (pH 3.5; 10mM), acetonitrile and methanol pumped at a flow rate 0.7mLmin^-1.The detection was performed on API4000 triple quadrupole tandem mass spectrometer using multiple reaction monitoring (MRM) positive electrospray ionization interface. The method was validated according to FDA guidelines for bio-analytical methods with respect to linearity, accuracy, precision, selectivity, carry-over, stability and dilution integrity. Linearity was obtained over a concentration range of 0.1-1000, 0.3-3000 and 3.0-3000ngmL^-1 for LED, SOF and GS-331007; respectively by applying weighted least-squares linear regression method (1/x²). The wider range of quantification in a shorter period of separation time less than 5.0min allowed monitoring the serum concentration of analytes up to 144h. The proposed method can be successfully applied for pharmacokinetic and bioequivalence studies in healthy human volunteers.

Simultaneous determination of newly developed antiviral agents in pharmaceutical formulations by HPLC-DAD

Background

Ombitasvir/paritaprevir/ritonavir/dasabuvir (Viekira Pak^®) are the newest medicines approved for use in the treatment of hepatitis C virus (HCV) and are available in tablet form as an oral combination. Specifically, these agents are indicated in the treatment of HCV in patients with genotype 1 infection. Due to the therapeutic importance and increased use of Viekira Pak, proper methods for its determination in bulk and pharmaceutical formulations must be developed.

Results

The present study describes the development and validation of a simple, rapid, selective and economical reverse phase high performance liquid chromatography-diode array detection (HPLC-DAD) method for the simultaneous determination of paritaprevir (PAR), ombitasvir (OMB), dasabuvir(DAS) and ritonavir (RIT) in bulk and pharmaceutical preparations. The proposed method was carried out using an RPC₁₈ column (150 × 4.5 mm, 3.5 μ), with a mobile phase consisting of 10 mM phosphate buffer (pH 7)and acetonitrile (35:65, v/v) at a flow rate of 1 ml/min and a detection wavelength of 254 nm. Sorafenib (SOR) was selected as the internal standard to ensure that the quantitative performance was high. The method was validated based on its specificity, linearity, limit of detection, limit of quantitation, accuracy, precision, robustness and stability. The calibration curves for PAR, DAS, RIT and OMB were linear at 2.5–60, 1.25–30, 1.7–40 and 0.42–10 μg/ml, respectively, and all of the correlation coefficients were >0.999.

Conclusions

The proposed method was successfully applied for the determination of ombitasvir/paritaprevir/ritonavir/dasabuvirin tablets, without interference from the excipient peaks. Hence, the method can be applied for the routine quality control analysis of the studied drugs, either in bulk or dosed forms.Graphical abstract

Towards interference free HPLC-SERS for the trace analysis of drug metabolites in biological fluids

Sofosbuvir metabolite, 2'-deoxy-2'-fluoro-2'-C-methyluridine (PSI-6206) was studied for the first time by surface enhanced Raman spectroscopy (SERS) using the paper-based SERS substrate. The quantification limit of PSI-6206 by SERS was found to be 13ngL^-1 (R² value=0.959, RSD=5.23%). For the structural and quantitative analysis of PSI-6206 in blood plasma, an interference-free HPLC-SERS method was developed and compared to HPLC-DAD and HPLC-MS methods. The SERS quantification of the drug by the paper substrate was 4 orders of magnitude more sensitive than that by the diode array detector. In addition, the SERS detection provided unique structural identification of the drug in blood plasma, similar to Mass spectroscopy detector. Due to the disposable nature of the SERS substrate, the new method does not suffer from the known "memory effect" which is known to lead to false positive identification in traditional HPLC-SERS methods. Therefore, the presented HPLC-paper SERS platform holds great potential for the sensitive and cost effective determination of drugs and their metabolites in biological fluids.

Quantification of sofosbuvir in human serum by liquid chromatography with negative ionization mass spectrometry using the parent peak and its source-induced fragment: Application to a bioequivalence study

In the mass spectrometry of sofosbuvir, a new orally administered antihepatitis C drug, a weak peak is detected at the m/z value of the parent ion (m/z 530) as a result of in-source dissociation and current methods to its quantification, is based on monitoring of the parent peak using ultra high-performance liquid chromatography with tandem mass spectrometry. With these methods serum concentration of the drug is quantifiable only up to 4-5 h postdose. However, the fragmentation of the molecule generates a more stable ion at m/z 287 (base peak) with a signal intensity of about tenfold compared to the parent ion. Our study was aimed to improve sensitivity of analysis by acquisition of the m/z value of the daughter ion from which it originated instead of the parent molecule. This novelty allows us to measure serum concentrations of the drug for a longer time postdose and provides more opportunity for pharmacokinetic studies of sofosbuvir. Our method was linear over the concentration range of 2-2560 ng/mL of sofosbuvir in human serum with a limit of quantification of 2 ng/mL compared to 10 ng/mL reported previously. The coefficient variation values of both inter and intraday analysis were less than 13.8%, and the percentage error was less than 6.3.