In this study, the goal is to improve and verify a simple, sensitive, accurate spectrophotometric technique for the measurement of drug formulations and pure forms of donepezil HCl (DNP). The procedure is forming an ion-pair complex in an acetate buffer solution between donepezil and the dye erythrosine B. The resulting complex is then measured spectrophotometrically at a wavelength of maximum absorbance (λ max) of 527nm. Beer's law was found to be applicable in the concentration range of 0.2-1.2 mg/ml, with a high correlation coefficient (n=5) of 0.99813. This indicates a strong linear relationship between the concentration of Donepezil HCl and the absorbance values within the specified range. The limit of detection (LOD) for the drug was determined to be 0.95056 mg/ml, representing the lowest concentration at which the method can reliably detect the presence of Donepezil HCl. Additionally, the limit of quantification (LOQ) was established at 3.1685 mg/ml, indicating the lowest concentration at which accurate quantification can be achieved. The proposed method was subjected to validation for accuracy and precision, demonstrating its reliability and reproducibility. The developed spectrophotometric method has been successfully applied to the analysis of Donepezil in its pure form as well as in pharmaceutical dosage form