Kinetic Study of the Alkaline Degradation of Oseltamivir Phosphate and Valacyclovir Hydrochloride using Validated Stability Indicating HPLC

UPLC-PDA factorial design assisted method for simultaneous determination of oseltamivir, dexamethasone, and remdesivir in human plasma

A green and simple UPLC method was developed and optimized, adopting a factorial design for simultaneous determination of oseltamivir phosphate and remdesivir with dexamethasone as a co-administered drug in human plasma and using daclatasvir dihydrochloride as an internal standard within 5 min. The separation was established on UPLC column BEH C18 1.7 μm (2.1 × 100.0 mm) connected to UPLC pre-column BEH 1.7 μm (2.1 × 5.0 mm) at 50 °C with an injection volume of 10 μL. The photodiode array detector (PDA) was set at three wavelengths of 220, 315, and 245 nm for oseltamivir phosphate, the internal standard, and both dexamethasone and remdesivir, respectively. The mobile phase consisted of methanol and ammonium acetate solution (40 mM) adjusted to pH 4 in a ratio of 61.5:38.5 (v/v) with a flow rate of 0.25 mL min-1. The calibration curves were linear over 500.0-5000.0 ng mL-1 for oseltamivir phosphate, over 10.0-500.0 ng mL-1 and 500.0-5000.0 ng mL-1 for dexamethasone, and over 20.0-500 ng mL-1 and 500.0-5000.0 ng mL-1 for remdesivir. The Gibbs free energy and Van't Hoff plots were used to investigate the effect of column oven temperatures on retention times. Fluoride-EDTA anticoagulant showed inhibition activity on the esterase enzyme in plasma. The proposed method was validated according to the M10 ICH, FDA, and EMA's bioanalytical guidelines. According to Eco-score, GAPI, and AGREE criteria, the proposed method was considered acceptable green.

Development of UPLC method for simultaneous assay of some COVID-19 drugs utilizing novel instrumental standard addition and factorial design

A green, rapid, and simple RP-UPLC method was developed and optimized by full factorial design for the simultaneous separation of oseltamivir phosphate, daclatasivir dihydrochloride, and remdesivir, with dexamethasone as a co-administered drug. The separation was established on a UPLC column BEH C₁₈ 1.7 µm (2.1 × 100.0 mm) connected with a UPLC pre-column BEH 1.7 µm (2.1 × 5.0 mm) at 25 °C with an injection volume of 10 µL. The detector (PDA) was set at 239 nm. The mobile phase consisted of methanol and ammonium acetate (8.1818 mM) in a ratio of 75.7: 24.3 (v/v). The flow rate was set at 0.048 mL min^-1. The overall separation time was 9.5 min. The retention times of oseltamivir phosphate, dexamethasone, daclatasivir dihydrochloride, and remdesivir were 6.323 ± 0.145, 7.166 ± 0.036, 8.078 ± 0.124, and 8.572 ± 0.166 min (eight replicates), respectively. The proposed method demonstrated linearity in the ranges of 10.0-500.0 (ng mL^-1) and 0.5-30.0 (µg mL^-1) for oseltamivir phosphate, 50.0-5000.0 (ng mL^-1) for dexamethasone, 25.0-1000.0 (ng mL^-1) and 0.5-25.0 (µg mL^-1) for daclatasvir dihydrochlorde, and 10.0-500.0 (ng mL^-1) and 0.5-30.0 (µg mL^-1) for remdesivir. The coefficients of determination (R²) were greater than 0.9999, with percentage recoveries greater than 99.5% for each drug. The limits of quantitation were 6.4, 1.8, 7.8, and 1.6 ng mL^-1, and the limits of detection were 1.9, 0.5, 2.0, and 0.5 ng mL^-1 for oseltamivir phosphate, dexamethasone, daclatasivir dihydrochloride, and remdesivir, respectively. The proposed method was highly precise, as indicated by the low percentage of relative standard deviation values of less than 1.2% for each drug. The average content and uniformity of dosage units in the studied drugs' dosage forms were determined. The average contents of oseltamivir phosphate, dexamethasone, daclatasivir dihydrochloride, and remdesivir were nearly 93%, 102%, 99%, and 95%, respectively, while the uniformity of dosage unit values were nearly 92%, 102%, 101%, and 97%. Two novel methods were established in this work. The first method was used to assess the stability of standard solutions. This novel method was based on the slope of regression equations. The second was to evaluate the excipient's interference using an innovative instrumental standard addition method. The novel instrumental standard addition method was performed using the UPLC instrument program. It was more accurate, sensitive, time-saving, economical, and eco-friendly than the classic standard addition method. The results showed that the proposed method can estimate the tested drugs' concentrations without interference from their dosage form excipients. According to the Eco-score (more than 75), the Green Analytical Procedure Index (GAPI), and the AGREE criteria (total score of 0.77), the suggested method was considered eco-friendly.

A Lateral Flow Immunochromato-graphic Strip Test for Rapid Detection of Oseltamivir Phosphate in Egg and Chicken Meat

A lateral flow immunochromatographic strip test (LFIST) based on a competitive format was developed for rapid and sensitive on-site detection of oseltamivir phosphate (OP) residues in poultry product. The sensitivity (half inhibitory concentration, IC₅₀) of the LFIST in the detection of egg and chicken meat samples was confirmed to be 2.56 and 2.63 µg/kg, and the limit detection (LOD) value were 0.43 and 0.42 µg/kg, respectively. For intra-assay and inter-assay reproducibility, recoveries of OP spiked samples ranged between 82.8% and 91.2% with coefficients of variations (CV) less than 5.67% (intra-assay) and 6.52% (inter-assay). The performance of LFIST was comparable to high-performance liquid chromatography (HPLC) in a parallel testing of egg samples and chicken samples. LFIST takes less than 5 minutes, eliminates the dependency on professional personnel, and thus can be used as a surveillance tool for on-site detection of OP residues.