Determination of Favipiravir in Human Blood Plasma by HPLC-MS/MS

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.