A simple, rapid, precise, accurate and low-cost stability-indicating HPLC method with diode array detection (DAD) has been developed for the simultaneous estimation of Memantine (MEM) and Donepezil (DPZ) in the presence of their degraded products. The chromatographic conditions used herein were inertsil ODS (4.6 x 250mm, 5μ) and acetonitrile with 0.1% orthophosphoric acid at a ratio of 10:90 as the mobile phase, with 271 nm as the wavelength of estimation, using DAD detector and 1.0 ml/min flow rate. Chromatographic separation of the drugs was achieved within 3.2 minutes from all the degradants. The linearity concentration for this method was found to be in the range of 10-50μg/ml for both drugs. The validation of the proposed method was performed as per the International Conference on Harmonization (ICH) guidelines for linearity, accuracy, precision, robustness, limit of detection and limit of quantification. The sample drugs were subjected to various forced degradation methods such as acid and base hydrolysis, oxidation, thermal, and photolytic degradation by sunlight. The drug substances underwent mild degradation irrespective of the induced stress. The proposed method can be used to quantify target drugs on a regular basis in tablet formulations.
