Mucin is a complex glycoprotein consisting of a wide variety of functional groups that can interact with exogenous agents. The binding to mucin plays a crucial role in drug pharmacokinetics especially in diseases, such as cystic fibrosis (CF), where mucin is overexpressed. In this study, we have investigated the interaction between mucin and several drugs used in CF therapy. Protein-drug interaction was carried out by UV-Vis and fluorescence spectroscopy; quenching mechanism, binding constants, number of binding sites, thermodynamic parameters and binding distance of the interaction were obtained.