In this paper, an analytical method for the analysis of DXM degradation products in a pharmaceutical product was developed by applying QbD concept and including green chemistry principles. Considerations for method development and design were discussed in terms of resolution between the active pharmaceutical ingredient (API) and usual degradation products, peak efficiencies,and solvent consumption. Experimental designs were used to identify parameters most affecting method performances and to find the optimal operating conditions. A response surface methodology allowed determining the DS which was confirmed experimentally to prove method robustness. The method was then validated in terms of selectivity, linearity, accuracy, and intermediate repeatability.