Validated isocratic stability-indicating RP-HPLC method for concurrent remdesivir estimation in drug products used in bioavailability studies

This study presents a stability-indicating, isocratic RP-HPLC method for the quantitative analysis of remdesivir (RMD) in pharmaceutical formulations and bioavailability studies. The method was developed to ensure robustness, precision and accuracy across diverse matrices, including freeze-dried powders, microspheres, novasomes and biological samples like blood. Chromatographic separation was achieved using a Zorbax Eclipse Plus C-18 column (4.6 × 250 mm, 5 ?m) with a mobile phase of 1% trifluoroacetic acid (TFA) and acetonitrile (55:45) at a 1 mL/min flow rate. Detection was carried out at 254 nm using a variable wavelength detector (VWD). Validation followed current good manufacturing practices (cGMP), covering parameters such as system suitability, linearity, specificity, precision, accuracy, robustness and forced degradation. The method showed a retention time consistent with RMD standards, a limit of detection (LOD) of 0.73 µg/mL and a limit of quantification (LOQ) of 2.22 µg/mL. Excellent linearity (R² = 0.999) was observed in the 12-120 µg/mL range. Long-term and accelerated stability studies confirmed the method's capability to detect degradation products without interference. The validated method supports reliable routine quality control testing and pharmacokinetic studies, making it suitable for in-vivo bioavailability assessments of RMD formulations.