Development, Validation, and Quantification of Organic Impurities with Mass Balance in the Levodopa and Benserazide Hydrochloride Pharmaceutical Dosage Form

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed to determine organic impurities in a combination drug containing levodopa and benserazide, frequently used in the treatment of Parkinson’s disease. The determination of impurities holds significant importance in combination products, as their higher occurrence impacts both the quality and bio-efficacy of the drug products. Thus, the current RP-HPLC method aims to identify organic impurities, providing simplicity, effectiveness, and reproducibility. A Zorbax SB C18 column (4.6 × 250 mm, 5 μm) was utilized, with a flow rate of 1.0 mL/min and a detection wavelength of 220 nm. The analysis was conducted in isocratic mode with an ambient (25°C) column temperature and a 5°C autosampler temperature. Further, enhanced peak resolution was achieved by employing an iron pair agent. All impurities were effectively separated, and peak purity analysis confirmed the absence of interference for levodopa and benserazide. Accuracy, precision, and linearity were well within acceptable criteria, with the method signifying a correlation coefficient above 0.995 for known impurities of levodopa and benserazide. The method validation, following ICH quality guidelines, exhibited the specificity of the developed method, while the robustness study confirmed its reliability under diverse conditions. Thus, mutual results indicate the pragmatism and applicability of the developed method, reinforcing safe and efficacious therapeutics for patients.