Introduction. Favipiravir is an antiviral compound that inhibits the RNA-dependent polymerase and possesses antiviral properties against RNA viruses, including SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2). The new drug Areplivir® Zinc as a combination of favipiravir (200 mg) and zinc gluconate (70 mg) in the form of film-coated tablets has been developed by LLC "PROMOMED RUS", Russia. This combination of favipiravir and zinc gluconate could provide more effective treatment of COVID-19.Aim. The aim of the pharmacokinetics study is comparison between Areplivir® Zinc (INN: favipiravir + zinc gluconate), film-coated tablets (the manufacturer is JSC "Biokhimic", LLC "PROMOMED RUS" as registration certificate holder) and Areplivir® (INN: favipiravir), film-coated tablets (the manufacturer is JSC "Biokhimic", LLC "PROMOMED RUS" as registration certificate holder) to evaluate the effect of zinc on the favipiravir pharmacokinetics.Materials and methods. The clinical and analytical phases as well as pharmacokinetic analyses have been performed as a part of a phase I clinical trial. Chromatographic separation and detection of favipiravir were performed by high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) method using Nexera XR high-performance liquid chromatograph with triple quadrupole tandem mass spectrometer LCMS-8040 (Shimadzu Corporation, Japan). The validated analytical range of the method was 50.00–15 000.00 ng/mL in human plasma. The plasma zinc concentrations were measured by a biochemical method with the use of the kit «Zinc-Novo (50)» (JSC "Vector-Best", Russia). The descriptive statistics were calculated using Microsoft Excel (Microsoft Corporation, USA). The pharmacokinetic parameters, analysis of variance (ANOVA), 90 % confidence intervals (90 % CIs) and the intra-subject variability (CVintra) were calculated by R Project 3.5.1 software (package «bear», version 2.8.3-2), originally created by Hsin-ya Lee and Yung-jin Lee, Taiwan.Results and discussion. The 90 % confidence intervals of the ratios for Сmax and AUC(0–t) were 86.48–100.38 % and 103.77–119.47 %, respectively. The 90 % confidence intervals were all within the acceptance range of 80.00–125.00 % which means there is no effect of zinc on the favipiravir pharmacokinetics. The intra-subject variability (CVintra) of favipiravir for the pharmacokinetic parameters Cmax and AUC(0–t) were 15.06 % and 14.23 %.Conclusion. The results justified the subsequent phases of clinical trials of Areplivir® Zinc (INN: favipiravir + zinc gluconate), film-coated tablets (LLC "PROMOMED RUS", Russia). This combination of favipiravir and zinc could expand the existing armamentarium of antiviral drugs for the treatment of COVID-19.

Introduction. Semaglutide preparations are an important therapeutic option for patients suffering from type 2 diabetes mellitus and obesity due to their high efficacy and the expected increase in the prevalence of these diseases. Consequently, there is a growing need for the development of domestic analogs of semaglutide requiring bioequivalence studies. This study proposes the use of high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) as an alternative to the widely used immunoassay for the quantitative determination of semaglutide in human serum.Aim. To develop and validate a method for the quantitative determination of semaglutide in human serum using HPLC-MS/MS.Materials and methods. Serum sample preparation was based on protein precipitation using an acetonitrile-methanol mixture. Liraglutide was selected as the internal standard. The mobile phase consisted of 0.3% formic acid in water and acetonitrile. The stationary phase was represented by a Phenomenex Kinetex C18 chromatographic column 100×3.0 mm, 5 μm, 100 Å. Ionization of semaglutide and liraglutide was performed in positive electrospray mode. Detection was carried out in multiple reaction monitoring mode (MRM).Results. The method demonstrated high accuracy and precision, with relative error and relative standard deviation values of less than 15% across all quality control levels. The confirmed analytical ranges of the method were 0.50–200.00 ng/mL and 1.00–800.00 ng/mL. Over 3.400 volunteer samples were analyzed as part of the studies. Compared to the ELISA method, the proposed method provides higher selectivity and reproducibility of measurements.Conclusions. The method has been developed that provides reproducible quantitative determination of semaglutide in human blood serum. The method was validated in accordance with EAEU requirements and was successfully applied in bioequivalence studies of semaglutide GP40331 (GEROPHARM LLC, Russia). The method is suitable for conducting pharmacokinetic studies of other semaglutide preparations.

Introduction. The pandemic of the new coronavirus infection COVID-19 (Coronavirus Disease 2019) was caused by a single-stranded RNA virus SARS-CoV-2 (Severe acute respiratory syndrome-related coronavirus 2). Molnupiravir is an antiviral drug with activity against RNA viruses including SARS-CoV-2. Molnupiravir exerts the antiviral effect by introducing copy errors during viral RNA replication – by that the replication of SARS-CoV-2 inhibits. For oral administration of molnupiravir the drug Esperavir® has been registered in Russia.Aim. The aim is pharmacokinetics study of Esperavir®, capsules 200 mg (the manufacturer is JSC "Biokhimic", LLC "PROMOMED RUS", Russia, as registration certificate holder) by a single dose (800 mg) and multiple doses oral administration (800 mg twice a day with a gap of 12 hours between doses) in healthy volunteers in a phase I pharmacokinetics study, comparison the obtained data of pharmacokinetic parameters with the literature data.Materials and methods. The clinical and analytical phases of the pharmacokinetic study as well as pharmacokinetic analyses have been performed as a part of a clinical trial of the drug Esperavir®, capsules 200 mg (the manufacturer is JSC "Biokhimic", LLC "PROMOMED RUS", Russia, as registration certificate holder). Chromatographic separation and detection by Nexera XR high-performance liquid chromatograph with triple quadrupole tandem mass spectrometry LCMS-8040 (Shimadzu Corporation, Japan). The pharmacokinetic parameters were calculated with the Boomer pharmacokinetic analysis add-in for Microsoft Excel (Department of Pharmacokinetics and Drug Metabolism, Allergan, Irvine, CA 92606, USA). Descriptive pharmacokinetic statistics were calculated with Microsoft Excel (Microsoft Corporation, USA).Results and discussion. Pharmacokinetic parameters for cohort 1 (800 mg single dose of Esperavir®) and for cohort 2 (800 mg of Esperavir® twice a day with a gap of 12 hours between doses) were calculated. Averaged pharmacokinetic profiles of mean NHC concentrations over time in linear and log-linear scales were plotted. The geometric mean of Cmax and T1/2, the median, minimum and maximum of Tmax showed the comparability of the obtained data after a single dose administration of 800 mg of Esperavir® and the available literature data.Conclusion. According to the concentrations from the analytical phase of the pharmacokinetic study the pharmacokinetic parameters were calculated, averaged pharmacokinetic profiles in linear and log-linear scales were plotted after a single dose and multiple doses of the drug Esperavir®, capsules (the manufacturer is JSC "Biokhimic", LLC "PROMOMED RUS", Russia, as registration certificate holder). The comparability of the obtained data and the available literature data was shown. The results justified the study of the subsequent phases of clinical trials of Esperavir®.

Introduction. COVID-19 (Coronavirus disease 2019) almost 4 years after he start of the pandemic is still a significant public health problem. SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) that causes COVID-19 continues to mutate and spread throughout the world. Molnupiravir and favipiravir have been shown to be efficacious against variety of RNA viruses including the SARS-CoV-2. The Ministry of Health of the Russian Federation approved the use of these drugs as a treatment of COVID-19. The developed drug contains the combination of two antiviral agents with different mechanisms of suppressing viral RNA replication, which suggests efficacy against the vast majority of ARVI pathogens found in the human population including SARS-CoV-2 and influenza.Aim. The aim of the pharmacokinetics study is comparison between JTBC00301 (INN: molnupiravir + favipiravir), film-coated tablets (LLC "PROMOMED RUS", Russia), Esperavir® (INN: molnupiravir), capsules (LLC "PROMOMED RUS", Russia) and Areplivir® (INN: favipiravir), film-coated tablets (LLC "PROMOMED RUS", Russia) to evaluate the impact of monocomponents on each other's pharmacokinetics.Materials and methods. The clinical and analytical phases as well as pharmacokinetic analyses have been performed as a part of a phase I, randomized, open-label, 3-period crossover study of drug JTBC00301 (INN: molnupiravir + favipiravir), film-coated tablets, 400 + 400 mg (LLC "PROMOMED RUS", Russia). The plasma concentration of β-D-N4-hydroxycytidine (NHC), the active metabolite of molnupiravir and favipiravir were determined in 42 healthy volunteers after taking the test drug JTBC00301 (1 tablet of 400 + 400 mg), the reference drug Esperavir® (2 capsules of 200 mg) and the reference drug Areplivir® (2 tablets of 200 mg). The descriptive statistics were calculated using Microsoft Excel (Microsoft Corporation, USA). The pharmacokinetic parameters, analysis of variance (ANOVA), the intra-subject coefficient of variation (CVintra) and 90 % confidence intervals (90 % CI) were calculated by R Project 3.5.1 software (package «bear», version 2.8.3-2), originally created by Hsin-ya Lee and Yung-jin Lee, Taiwan.Results and discussion. Pharmacokinetic parameters of NHC and favipiravir were determined, averaged pharmacokinetic profiles in linear and log-linear scales were plotted, analysis of variance was carried out. The 90% CIs for geometric mean ratios of Сmax and AUC(0–t) for NHC and favipiravir were all within the acceptance range of 80–125 % which means there is no effect of monocomponents on each other’s pharmacokinetics.Conclusion. The development of the fixed-dose drug combination of molnupiravir and favipiravir has great potential as it may allow to increase the safety profile and improve the tolerability of therapy as well as increase the effectiveness of antiviral therapy. The results justified the study of the subsequent phases of clinical trials of JTBC00301 (INN: molnupiravir + favipiravir), film-coated tablets, 400 + 400 mg (LLC "PROMOMED RUS", Russia).

Introduction. Etmaben is a malonic acid derivative that has shown cardiotropic activity and is a promising candidate for treating ischemic heart disease and chronic heart failure. It is currently undergoing Phase I clinical trials, and its pharmacokinetics have not yet been studied in humans.Aim. The aim of the study is to investigate the pharmacokinetics of Etmaben, film-coated tablets, 300 mg (SPCPU, Russia) in healthy volunteers after fasting administration of different doses following both single and multiple dosing over a 7-day period.Materials and methods. The open-label, non-randomized clinical trial involved 48 healthy volunteers divided into 6 cohorts. Volunteers in cohort 1 received a single dose of 600 mg of etmaben, cohort 2 received 900 mg, and cohort 3 received 1200 mg. Cohorts 4, 5, and 6 received daily doses of 600 mg, 900 mg, and 1200 mg, respectively. Plasma concentrations of etmaben were measured using high-performance liquid chromatography with tandem mass spectrometry detection. Pharmacokinetic parameters were calculated using Microsoft Excel with the Boomer extension (Department of Pharmacokinetics and Drug Metabolism, Allergan, Irvine, CA 92606, USA).Results and discussion. Pharmacokinetic parameters were calculated for 6 cohorts of 8 volunteers after single and multiple dosing of Etmaben at doses of 600, 900, and 1200 mg. The maximum plasma concentration (Cmax) of etmaben was reached on average within 0.5 h. Cmax values ranged from 2.708 ± 1.461 µg/mL to 19.871 ± 4.415 µg/mL. The maximum half-life was 0.874 ± 0.236 h, with an elimination rate constant not exceeding 1.053 ± 0.149 h–1. The mean residence time (MRT) of etmaben in plasma did not exceed 1.527 ± 0.272 h. The average volume of distribution was above 45 L, and clearance exceeded 42 L, indicating significant tissue distribution and rapid drug elimination. Due to low area under the curve values and high elimination rates, the accumulation of etmaben is minimal.Conclusion. Pharmacokinetic parameters were calculated, and averaged pharmacokinetic profiles were constructed in linear and semilogarithmic coordinates after single and multiple dosing of various etmaben doses. This study represents the first investigation of etmaben pharmacokinetics in humans, paving the way for subsequent clinical trials.

Introduction. The use of tofacitinib as a pharmacological treatment for rheumatoid arthritis remains relevant in the light of the predicted increase in prevalence of the disease. At the same time, due to the withdrawal of several foreign pharmaceutical companies from the Russian pharmaceutical market, there has been a heightened demand for domestically produced medications, including generic formulations of tofacitinib. Registration of generic drugs necessitates the conduct of bioanalytical studies. Development and validation of a method for quantifying the analyte in biosamples remains to be a crucial part of the bioequivalence studies. Aim. The aim of this research is to develop and validate a method for the quantitative determination of tofacitinib in human plasma using high-performance liquid chromatography as the separation system coupled with a tandem mass spectrometer for detection purposes. Materials and methods. Biosample preparation was based on plasma proteins precipitation using acetonitrile. Baricitinib was selected as an internal standard. The analytical range of the method was 1.00 to 200.00 ng/mL and was further expanded to 0.30 to 200.00 ng/mL during the analytical phase of the study. The mobile phase consisted of water and acetonitrile, both acidified with formic acid (0.1 % v/v). The stationary phase was a Phenomenex Kinetex C 18 column [100 × 3.0 mm, with a particle size of 5 µm (Phenomenex, USA)]. Sample separation and detection were carried out using high-performance liquid chromatography coupled with a tandem mass spectrometry (HPLC-MS/MS), operating in positive ion mode. The multiple reaction monitoring (MRM) transitions selected for the analyte and the internal standard were 313.30 to 173.00 m/z and 371.90 to 186.00 m/z, respectively. Results and discussion. The developed assay was validated in accordance with the current requirements of regulatory documentation from the EAEU (Eurasian Economic Union), FDA (US Food and Drug Administration), and EMA (European Medicines Agency) with the following parameters being evaluated: selectivity, specificity, carry-over, matrix effect, recovery, calibration curve, lower limit of quantitation, accuracy, precision, stability. The validated method was applied in the analytical part of a bioequivalence study of domestically produced generic tofacitinib. Conclusion. A method for the quantitative determination of tofacitinib in human blood plasma with an analytical range of 0.30–200.00 ng/mL was developed and validated. Application of the assay during the analytical phase of bioequivalence study of generic tofacitinib confirms the possibility of using the method in similar bioanalytical investigations.

Introduction. Etmaben is a promising drug for the treatment of cardiovascular diseases, widely studied in preclinical studies. In order to conduct phase I clinical trials, it is necessary to develop a bioanalytical method for the quantitative determination of etmaben in human blood plasma. Aim. The aim of the study is to develop and validate a method for the quantitative determination of etmaben in human blood plasma using high-performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS) for the pharmacokinetic study. Materials and methods. The determination of etmaben in human blood plasma was carried out on a Nexera XR chromatograph with a mass-selective detector LCMS-8040 (Shimadzu Corporation, Japan). Sample preparation: precipitation with acetonitrile. Internal standard: promethazine. Column: Luna C18, 100 Å, 50 × 2.00 mm, 5 µm. Elution in gradient mode at a flow rate of 1.00 mL/min. Mobile phase: 0.1 % formic acid solution in water (eluent A), 0.1 % formic acid solution in acetonitrile (eluent B). Retention time for etmaben and promethazine is approximately 1.18 min and 1.15 min, respectively. Total chromatogram registration time: 4.00 min. Ionization method and mode: electrospray; negative mode for etmaben, positive mode for promethazine. Detection was carried out in the mode of multiple reaction monitoring (MRM): 249.90 → 92.15 m/z; 249.90 → 160.20 m/z (etmaben); 284.95 → 197.95 m/z (promethazine). Results and discussion. We have developed, for the first time, a method for determining etmaben and performed its full and partial validation according to current regulatory requirements. Conclusion. The method for determining etmaben in human blood plasma with a confirmed analytical range of 0.250–30.000 µg/mL has been developed and validated. The confirmed analytical range of the method based on the results of the partial validation was 0.040–35.000 µg/mL. The method was successfully applied in phase I clinical trials and can be used for other pharmacokinetic studies of etmaben.

Introduction. Apixaban is an anticoagulant used in a number of thromboembolic diseases with an improved benefit-to-risk ratio, according to multiple clinical studies. Due to the prescription of apixaban as antithrombotic therapy in patients with COVID-19, an increase in its use has been observed. Thus, due to the widespread use of apixaban and the need to conduct pharmacokinetic and bioequivalence studies of the drug, it is important to develop and validate a simple and sensitive method for the quantitative determination of apixaban in human blood plasma.Aim. The aim of the study is to develop and validate a method for the determination of apixaban in human blood plasma using high-performance liquid chromatography with tandem mass selective detection (HPLC-MS/MS) for the subsequent bioanalytical study.Materials and methods. The determination of apixaban in human plasma was carried out by HPLC-MS/MS with rivaroxaban as an internal standard. The method of protein precipitation with acetonitrile was used as sample preparation. Mobile phase: 0.1 % solution of formic acid in water (eluent A); 0.1 % solution of formic acid in acetonitrile (eluent B). The total run time was 3.00 min. Column: Shim-pack Velox Biphenyl; 2.7 µm; 50 × 2.1 mm. Ionization source: electrospray with positive ionization mode. MRM transitions: 460.15 → 443.10 m/z (apixaban); 436.05 → 144.95 m/z (rivaroxaban).Results and discussion. The developed method was validated in accordance with the EAEU requirements for the following parameters: selectivity, calibration curve, accuracy and precision, lower limit of quantitation, suitability of standard samples, matrix effect, recovery, stability, carry-over, dilution effects. The parameters met the acceptance criteria.Conclusion. The confirmed analytical range of the developed and validated method was 1.00–300.00 ng/mL in blood plasma. The method for determining apixaban in blood plasma is simple and sensitive. This method was tested during the analytical part of the bioanalytical study and can be used to conduct other pharmacokinetic studies of apixaban drugs.

Introduction. Obesity is a growing public health issue in Russia, increasing the risk of cardiovascular diseases, type 2 diabetes, and hypertension. Controlling obesity involves lifestyle changes and pharmacotherapy. Semaglutide, an effective obesity treatment, stimulates insulin production and reduces appetite. Developing a generic semaglutide preparation will improve its availability in Russia.Aim. To study the comparative pharmacokinetics, bioequivalence, safety and tolerability of semaglutide products GP40331 and Wegovy using concentrations of 0.68 and 3.2 mg/ml in healthy volunteers under fasting conditions.Materials and methods. Bioequivalence studies, conducted per Good Clinical Practice, were open-label, randomized, and involved healthy male volunteers. Subjects received semaglutide at single doses of 0.25 mg (0.68 mg/ml) and 0.5 mg (3.2 mg/ml) under fasting. Bioequivalence was determined by the 90% CI of the ratios of geometric mean values of the primary pharmacokinetic parameters (AUC0-t, Cmax). Semaglutide concentrations were measured using high-performance liquid chromatography with tandem mass spectrometry.Results. The 90% CI values for the ratios of geometric means of the primary PK parameters of semaglutide were 90.22–110.29 and 86.48–108.98% (0.68 mg/ml) and 90.62–115.71 and 92.86–113.51% (3.2 mg/ml). Comparable safety was proven for both concentrations.Conclusion. GP40331 and Wegovy at 0.68 and 3.2 mg/mL are bioequivalent and equally safe.

Introduction. The novel coronavirus infection COVID-19 (Coronavirus Disease 2019) is caused by an enveloped, positive-sense, single-stranded ribonucleic acid (RNA) virus SARS-CoV-2 (severe acute respiratory syndrome-related coronavirus 2). Favipiravir is the antiviral drug recommended for etiotropic treatment of COVID-19. Parenteral therapy has advantages over the other routes of the drug administration: there are no interaction with food and digestive enzymes, may be used for patients with diseases of the digestive system and unconscious patients. For parenteral drug administration of favipiravir the drug "Areplivir" has been registered in Russia.Aim. The aim is pharmacokinetics study of drug "Areplivir", a lyophilisate for the preparation of a concentrate for the infusion solution (the manufacturer is JSC "Biokhimic", LLC "Promomed RUS" as registration certificate holder) by intravenous infusion in healthy volunteers in a phase I pharmacokinetics study.Materials and methods. The clinical and analytical phases of the pharmacokinetic study as well as pharmacokinetic analyses have been performed as part of a clinical trial of the drug "Areplivir" in different doses, a lyophilisate for the preparation of a concentrate for the infusion solution (LLC "Promomed RUS", Russia). Chromatographic separation and detection were carried out on a LC-2040C high-performance liquid chromatograph (Shimadzu Corporation, Japan) with a built-in UV detector, a low-pressure four-component gradient pump, a degasser, an autosampler, a column thermostat and a controller. The pharmacokinetic parameters were calculated with the Boomer pharmacokinetic analysis add-in for Microsoft Excel (Department of Pharmacokinetics and Drug Metabolism, Allergan, Irvine, CA 92606, USA). Descriptive pharmacokinetic statistics were calculated with Microsoft Excel (Microsoft Corporation, USA). Correlation and Regression Analysis were conducted with IBM SPSS Statistics (version 23.0), IBM, USA.Results and discussion. For single dose administration of 400, 800, 1600 and 1800 mg in 4 cohorts of 5 volunteers pharmacokinetic parameters were calculated. For Cmax and an administered dose the strong correlation coefficient on the Chaddock scale (r = 0,98; p = 0,02; r – Pearson correlation coefficient; p – the reached significance value) and the determination coefficient (R2 = 0,96; F = 45,97; p = 0,02; R2 – determination coefficient; F – the actual value of the Fisher's criterion) were statistically significant. For AUC0-t and an administered dose the strong correlation coefficient on the Chaddock scale (r = 0,97; p = 0,03) and the determination coefficient (R2 = 0,94; F = 33,54; p = 0,03) were statistically significant. The obtained results show the linearity of Cmax and an administered dose and the linearity of AUC0-t and an administered dose (400–1800 mg).Conclusion. According to the concentrations of favipiravir from the analytical phase of the pharmacokinetic study the pharmacokinetic parameters were calculated, averaged pharmacokinetic profiles in linear and log-linear scales were plotted after single dose administrations of the drug "Areplivir" in different doses, a lyophilisate for the preparation of a concentrate for the infusion solution (LLC "Promomed RUS", Russia). The linearity of Cmax and a single administered dose and the linearity of AUC0-t and a single administered dose of the drug "Areplivir" have been demonstrated for doses of 400 to 1800 mg. The results justified the study of multiple dose administration of "AREPLIVIR" and the subsequent phases of clinical trials.

Introduction. Citicoline is an endogenous nucleoside consisting of cytidine and choline linked by a diphosphate bridge that is involved in the synthesis of membrane phospholipids. Drugs containing citicoline have neuroprotective and neurometabolic effects and are used for the treatment of a wide range of neurological disorders. In its turn, bioequivalence study is a pathway to register a generic citicoline drug in Russian Federation. Aim. The aim of the study was to investigate the comparative pharmacokinetics (PK) and bioequivalence of two citicoline-containing drugs GP30121 and Ceraxon® in healthy male volunteers when taken on an empty stomach. Materials and methods. We evaluated the pharmacokinetics of citicoline-containing drugs corrected for endogenous analyte (uridine) level using an adaptive design. We determined uridine concentration by high-performance liquid chromatography with mass spectrometric detection. We used R Project software, version 3.6.3. for performing statistical analysis for the study. Results and discussion. GP30121 and Ceraxon® exhibited similar PK profiles. It was shown that the values of 94.12 % confidence interval (CI) at α = 0.0294 for the geometric mean ratios for the primary PK parameters of the main metabolite of the active ingredient of the investigated drugs were fully contained within the predefined equivalence limits of 80.00–125.00 %. Conclusion. The study demonstrates bioequivalence of GP30121 and Ceraxon® proving the approach with the correction for endogenous analyte could be considered in studies of other drugs.

Целью исследования являлась разработка и валидация методики количественного определения фавипиравира - лекарственного средства, применяемого в терапии новой коронавирусной инфекции - в плазме крови человека методом высокоэффективной жидкостной хроматографии с УФ-спектрофотометрическим детектированием (ВЭЖХ-УФ) с целью последующего изучения фармакокинетики препаратов фавипиравира. Разработанная методика валидирована в соответствии с правилами Евразийского экономического союза (ЕАЭС).

Introduction. Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the SARS-CoV-2 virus (severe acute respiratory syndrome-related coronavirus 2). COVID-19 is now expected to stay with us for many years as a recurring disease. Molnupiravir and favipiravir are oral antiviral drugs with anti-RNA polymerase activity. The Russian Health Ministry has approved molnupiravir and favipiravir for the treatment of COVID-19. The study describes development and validation of high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) method for the simultaneous determination of β-D-N4-Hydroxycytidine and favipiravir in human blood plasma. The method could be applied in pharmacokinetic study of molnupiravir and favipiravir.Aim. The aim of this study is to develop and validate a HPLC-MS/MS bioanalytical method for the determination of β-D-N4-Hydroxycytidine and favipiravir in human plasma.Materials and methods. The determination of β-D-N4-Hydroxycytidine and favipiravir in human plasma by HPLC-MS/MS. The samples were processed by 0.1 % formic acid in acetonitrile. Internal standard: promethazine. Mobile phase: 0.01 mol/L Ammonium formate buffer solution (Eluent A), 0.1 % formic acid and 0.08 % aqueous ammonia in water/acetonitrile 10 : 90 (Eluent B). Column: Shim-pack GWS C18, 150 × 4.6 mm, 5 μm. Analytical range: 50.00–10000.00 ng/mL for β-D-N4-Hydroxycytidine, 250.00–20000.00 ng/mL for favipiravir in human plasma. Ionization source: electrospray ionization. Detection conditions: 260.00 m/z → 82.10 m/z, 260.00 m/z → 111.00 m/z, 260.00 m/z → 127.95 m/z (β-D-N4-Hydroxycytidine); 156.15 m/z → 65.95 m/z, 156.15 m/z → 85.00 m/z, 156.15 m/z → 113.10 m/z (favipiravir); 285.05 m/z → 198.05 m/z (promethazine).Results and discussion. This method was validated by selectivity, suitability of reference standard, matrix effect, calibration curve, accuracy, precision, spike recovery, the lower limit of quantification, carry-over effect and stability.Conclusion. The HPLC-MS/MS method for quantitative determination of β-D-N4-Hydroxycytidine and favipiravir in human plasma was developed and validated. The analytical range was 50.00–10000.00 ng/mL for β-D-N4-Hydroxycytidine, 250.00–20000.00 ng/mL for favipiravir in human plasma. This method was applied to investigate the pharmacokinetics of molnupiravir and favipiravir.

Целью исследования являлась разработка и валидация методики определения лаппаконитина и N-дезацетиллаппаконитина в плазме крови человека для изучения фармакокинетики препарата лаппаконитина гидробромида, таблетки пролонгированного действия 25 мг.

Introduction. Favipiravir is one of the most well-known broad-spectrum drugs against many RNA viruses, including the severe acute respiratory syndrome virus 2 [severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)]. Due to its structure, favipiravir is embedded in the RNA of the virus and blocks its further replication in the cell of the human body. Favipiravir is also included in the list of vital and essential medicines, which confirms the importance for Russian healthcare of this drug in the fight against common RNA viruses. We have already published bioanalytical methods for determining favipiravir in human blood plasma by high-performance liquid chromatography with an ultraviolet detector (HPLC–UV) in order to study the pharmacokinetics of favipiravir with parenteral administration (the analytical range of the technique was 0.25–200.00 µg/ ml for the dosage of favipiravir 400 mg in 1 vial of lyophilizate for the preparation of concentrate for the preparation of solution for infusions) and by HPLC with tandem mass-selective detection (HPLC-MS/MS) in order to study the pharmacokinetics of β-D-N4-hydroxycytidine and favipiravir in their joint determination in blood plasma with oral administration (the analytical range of the technique was 250.00–20000.00 ng/ml for the dosage of favipiravir 400 mg in 1 tablet). The expectation of low favipiravir’s concentrations (the dosage of favipiravir in the drugs in question is 200 mg in 1 tablet in this study) and, in this regard, the expansion of the range by reducing the value of the lower limit of quantitative determination (LLOQ) used in this study necessitates the development of another method. Therefore, this study is given the development and validation of a method for determining favipiravir in human blood plasma by HPLC-MS/MS with an analytical range of 50.00–15000.00 ng/ml. Aim. The aim of this study is to develop a method for quantitative determination of favipiravir in human blood plasma by HPLC-MS/MS for further for further researches of pharmacokinetics and bioequivalence of drugs. Materials and methods. In the process of sample preparation, a method of proteins precipitation with methanol was used. A solution labeled with stable isotopes of favipiravir-13C3 was used as an internal standard, the mobile phase was a 0.1 % solution of formic acid in water (eluent A) and methanol (eluent B). Chromatographic column – Phenomenex Kinetex C18, 100×3.0 mm. The determination of favipiravir in human blood plasma was carried out by HPLC using a tandem mass spectrometric detector with a triple quadrupole. The analytical range for favipiravir is 50.00– 15000.00 ng/ml in human blood plasma. Results and discussion. This method was validated by selectivity, calibration curve, accuracy, precision, matrix effect, spike recovery, carry-over effect, the lower limit of quantification and stability. Conclusion. A method of quantitative favipiravir’s determination in human blood plasma by HPLC-MS/MS with a confirmed analytical range of 50.00–15000.00 ng/ml in human blood plasma has been developed and validated. This method allows using it for the analytical part of pharmacokinetics and bioequivalence studies of drugs containing favipiravir in order to expand their range in the domestic pharmaceutical market.

Introduction. SARS-CoV-2 (severe acute respiratory syndrome-related coronavirus 2) is expected to remain a persistent global threat. Therefore, development of coronavirus disease 2019 (COVID-19) drugs is the most urgent global issue. Nirmatrelvir and ritonavir combination is an oral antiviral drug combination with activity against SARS-CoV-2. Nirmatrelvir and ritonavir combination is highly efficacious in reducing the risk of COVID-19. The study describes development and validation of high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) method for the simultaneous determination of nirmatrelvir and ritonavir in human blood plasma. The method could be applied in pharmacokinetic study of nirmatrelvir and ritonavir. Aim. The aim of this study is to develop and validate a HPLC-MS/MS bioanalytical method for the determination of nirmatrelvir and ritonavir in human plasma. Materials and methods. The determination of nirmatrelvir and ritonavir in human plasma by HPLC-MS/MS. The samples were processed by acetonitrile protein precipitation. Internal standard: promethazine. Mobile phase: 0.1% formic acid solution in water (Eluent A), 0.1% formic acid in acetonitrile (Eluent B). Column: Phenomenex Luna C18 50 × 2.0 mm, 5 μm. Analytical range: 50.00–10000.00 ng/mL for nirmatrelvir, 5.00–1000.00 ng/mL for ritonavir in human plasma. Ionization source and ionization: electrospray ionization, positive. Detection conditions: 499.90 → 110.10 m/z, 499.90 → 319.20 m/z (nirmatrelvir), 720.90 → 426.00 m/z, 720.90 → 296.20 m/z, 720.90 → 268.10 m/z, 720.90 → 197.10 m/z, 720.90 → 139.90 m/z (ritonavir), 285.15 → 198.05 m/z (promethazine). Results and discussion. This method was validated for selectivity, matrix effect, calibration curve, accuracy, precision, spike recovery, the lower limit of quantification, carry-over effect and stability. Conclusion. The HPLC-MS/MS method for quantitative determination of nirmatrelvir and ritonavir in human plasma was developed and validated. The analytical range was 50.00–10000.00 ng/mL for nirmatrelvir, 5.00–1000.00 ng/mL for ritonavir in human plasma. This method was applied to investigate the pharmacokinetics of nirmatrelvir and ritonavir.

Introduction. Coronavirus disease (COVID-19) is an acute infectious disease caused by SARS-CoV-2 (severe acute respiratory syndrome-related coronavirus 2). Favipiravir is a synthetic prodrug with antiviral activity used for the treatment of COVID-19. There are oral and parenteral dosage forms of favipiravir. Compared with oral administration, parenteral administration has some advantages. Developing a method for the determination of favipiravir in human blood plasma is necessary for performing the analytical part of clinical studies of favipiravir for parenteral administration as an infusion, studying pharmacokinetics, and choosing the optimal dosage of the drug.Aim. The aim of this study is to develop and validate a method for quantitative determination of favipiravir in human plasma by high-performance liquid chromatography with ultraviolet detection (HPLC-UV) for pharmacokinetic studies.Materials and methods. Determination of favipiravir in human plasma by HPLC-UV. The UV detection was set at 323 ± 2 nm. The samples were processed by methanol protein precipitation. Internal standard: raltegravir. Mobile phase: 0.1 % formic acid in water with 0.08 % aqueous ammonia (eluent A), 0.1 % formic acid in acetonitrile with 0.08 % aqueous ammonia (eluent B). Column: Phenomenex Kinetex®, C18, 150 × 4.6 mm, 5 μm. Analytical range: 0.25–200.00 μg/mL.Results and discussion. This method was validated by selectivity, calibration curve, accuracy, precision, spike recovery, the lower limit of quantification, carry-over effect and stability.Conclusion. We developed and validated the method of quantitative determination of favipiravir in human plasma by HPLC-UV. The analytical range was 0.25–200.00 μg/mL in human plasma. The method could be applied in pharmacokinetics studies of favipiravir.

Introductio n. Deferasirox is one of the most well-known complexing drugs chelators and is successfully used in chelating therapy for the treatment of excess iron in the human body. Deferasirox is also included in the list of vital and essential medicines, which indicates the importance of this drug for Russian healthcare. In this document, there are drugs only from a foreign manufacturer, therefore, within the framework of the trend towards import substitution, the development of deferasirox preparations of domestic production is a necessary and promising direction. In this connection, there is a need to develop a method that allows quantifying deferasirox in human blood plasma with minimal time and resource costs as part of a pharmacokinetic study. Aim. The aim of this study is to develop a method for quantitative determination of deferasirox in human blood plasma by high performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) for further bioequivalence studies. Materials and methods. Determination of the deferasirox in human blood plasma was carried out by HPLC-UV. The method of proteins precipitation by acetonitrile was used as a sample preparation. Erlotinib solution was used as an internal standard. Mobile phase: 0.3 % solution of orthophosphoric acid in water, brought to pH 3.0 (eluent A) and 0.1 % solution of formic acid in acetonitrile (eluent B). Column was Symmetry®, 75 × 4,6 mm (Waters, США) . Analytical range of the technique for deferasirox was 0.25–70.00 µg/ml in human blood plasma. Detection was carried out using a UV detector at an absorption wavelength of 299 ± 2 nm. Results and discussion. This method was validated by selectivity, calibration curve, accuracy, precision, spike recovery, the lower limit of quantification, carry-over effect and stability. Conclusion. A method of quantitative determination of deferasirox in human blood plasma was developed and validated by HPLC-UV. The analytical range was 0.25–70.00 µg/ml in human blood plasma. This method was used as part of a study of the pharmacokinetics and bioequivalence of deferasirox drugs.

Introduction.Allaforte® (JSC "Pharmcenter VILAR", Russia) is an antiarrhythmic long-acting drug. The dosage form of the drug Allaforte® provides a decrease in the frequency of taking the drug and also reduces the risk of side effects. It is relevant when taking antiarrhythmic drugs of the IC class. However, the pharmacokinetics of this drug has not been studied on humans. Therefore, it is important to fully study the pharmacokinetics to ensure the maximum efficacy and safety of arrhythmia therapy.Aim.The aim is pharmacokinetics study of long-acting antiarrhythmic drug Allaforte® (JSC "Pharmcenter VILAR", Russia), 25 mg. Materials and methods. Concentration of lappaconitine and its active metabolite N-desacetyllappaconitine in human plasma determinates by high performance liquid chromatography with tandem mass-spectrometry. Pharmacokinetic parameters calculated by R Project 3.5.1 software (package «bear», version 2.8.3-2), originally created by Hsin-ya Lee and Yung-jin Lee, Taiwan.Results and discussion.Pharmacokinetic parameters of lappaconitine and N-desacetyllappaconitine were calculated. Averaged pharmacokinetic profiles (in linear and semi-log scale) of lappaconitine and N-desacetyllappaconitine after single administration under fasting were built. The means of the maximum concentrations (Cmax) determined in the blood plasma of volunteers after single administration Allaforte® are 5.09 ± 4.07 ng/ml for lappaconitine and 11.66 ± 6.21 ng/ml for N-deacetyllappaconitine (Mean ± SD). The peak time of the maximum concentrations (Tmax) is 4.43 ± 3.54 hours for lappaconitine and 4.04 ± 2.18 hours for N-deacetyllappaconitine. The means of the areas under the curve plasma concentration – time from 0 to 48 hours (AUC0-t) and under the curve plasma concentration–time from zero to infinity (AUC0-∞) of Allaforte® is 42.96 ± 34.48 ng ∙ h/ml and 71.24 ± 43.20 ng ∙ h/ml for lappaconitine; 167.42 ± 114.41 ng ∙ h/ml and 189.42 ± 115.20 ng ∙ h/ml for N-deacetyllappaconitine. Allaforte® was eliminated from blood plasma with means of terminal half-life (T1/2) 8.45 ± 5.10 hours for lappaconitine and 9.04 ± 2.57 hours for N-deacetyllappaconitine.Conclusion.Pharmacokinetics study of long-acting antiarrhythmic drug Allaforte® (JSC "Pharmcenter VILAR", Russia) after single administration was researched. Results of the study allows to conduct an effective therapy of arrhythmia by study drug and minimize side effects.

Introduction. Combined drugs have the greatest efficacy and safety in arterial hypertension treatment. The combination of candesartan and hydrochlorothiazide (AT1-receptor antagonist and a thiazide diuretic, respectively) provides high efficiency of antihypertensive combination therapy, therefore it is widely used in medical practice. Developing a method for simultaneous determination of candesartan and hydrochlorithiazide in human blood plasma is necessary for performing the analytical part of pharmacokinetic studies and bioequivalence studies of multicomponent drugs.Aim. The aim of this study is to develop a method for quantitative determination of candesartan and hydrochlorothiazide in human plasma by high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) for further bioequivalence studies.Materials and methods. Determination of candesartan and hydrochlorothiazide in human plasma by HPLC-MS/MS. The samples were processed by acetonitrile protein precipitation. Internal standard: mixed solution of valsartan and indapamide. Mobile phase: 0.1 % formic acid solution in water (eluent A), 0.1 % formic acid in acetonitrile (eluent B). Column: Phenomenex Luna Phenyl-Hexyl, 50x4.6 mm, 5 μm. Analytical range: 2.00–300.00 ng/mL for candesartan, 2.00–200.00 ng/mL for hydrochlorothiazide in human plasma. Ionization source: electrospray ionization. Detection conditions: 441.10 → 192.00 m/z, 441.10 → 263.15 m/z (candesartan), 295.85 → 269.00 m/z (hydrochlorothiazide), 436.00 → 207.05 m/z (valsartan), 363.85 → 132.10, 363.85 → 189.00 m/z (indapamide).Results and discussion. This method was validated by selectivity, matrix effect, calibration curve, accuracy, precision, spike recovery, the lower limit of quantification, carry-over effect and stability. The developed method meets the requirements for conducting bioequivalence studies of medicinal products within the framework of the Eurasian Economic Union.Conclusion. The analytical range was 2.00–300.00 ng/mL for candesartan, 2.00–200.00 ng/mL for hydrochlorothiazide in human plasma. The method was applied in BE study of the combination of candesartan and hydrochlorothiazide.