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.

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. 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.

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.

РезюмеВведение. Деферазирокс является одним из наиболее известных комплексообразующих лекарственных средств и успешно применяется в хелатирующей терапии для лечения избытка железа в организме человека. Также деферазирокс входит в перечень жизненно необходимых и важнейших лекарственных препаратов, что свидетельствует о значимости данного лекарственного средства для российского здравоохранения. В указанном перечне присутствуют препараты только зарубежного производителя, поэтому в рамках тенденции к импортозамещению разработка препаратов деферазирокса отечественного производства является необходимым и перспективным направлением. В связи с чем возникает необходимость разработки методики, позволяющей с минимальными временными и ресурсными затратами количественно определить деферазирокс в плазме крови человека в рамках фармакокинетического исследования. Цель. Целью исследования является разработка и валидация методики определения деферазирокса в плазме крови человека методом высокоэффективной жидкостной хроматографии с ультрафиолетовым детектированием (ВЭЖХ-УФ) для дальнейшего исследования фармакокинетики и биоэквивалентности лекарственных препаратов. Материалы и методы. Определение деферазирокса в плазме крови человека проводили методом ВЭЖХ-УФ. В качестве пробоподготовки был использован способ осаждения белков ацетонитрилом. Раствор эрлотиниба использовался в качестве внутреннего стандарта. Подвижная фаза: 0,3%-й раствор ортофосфорной кислоты в воде, доведенный до pH 3,0 (элюент А) и 0,1%-й раствор муравьиной кислоты в ацетонитриле (элюент В). Колонка: Symmetry®, 75 × 4,6 мм (Waters, США). Аналитический диапазон методики для деферазирокса: 0,25-70,00 мкг/мл в плазме крови. Детектирование проводилось с помощью УФ-детектора при длине волны поглощения 299 ± 2 нм. Результаты и обсуждение. Валидация разработанной методики проводилась по следующим валидационным параметрам: селективность, калибровочная кривая, точность, прецизионность, степень извлечения, нижний предел количественного определения, перенос пробы, стабильность (стабильность исходных и рабочих стандартных растворов аналита и внутреннего стандарта; краткосрочная стабильность; стабильность при трехкратной заморозке-разморозке аналита; долгосрочная стабильность аналита в матрице). Заключение. Была разработана и валидирована методика определения лекарственного средства деферазирокс в плазме крови человека методом ВЭЖХ-УФ. Аналитический диапазон методики был подтвержден и составил 0,25-70,00 мкг/мл для деферазирокса в плазме крови. Данная методика была использована в рамках проведения исследования фармакокинетики и биоэквивалентности препаратов деферазирокса.