Mixed Micellization, Spectra and Calculations of an Antiallergic Drug (Cetirizine Dihydrochloride) With Surfactants

ABSTRACT The interaction between antiallergic drug Cetirizine Dihydrochloride (CTZ) and cationic surfactants cetylpyridinium chloride monohydrate (CPC) and cetylpyridinium bromide (CPB) in aqueous solution was investigated. A tensiometric study was conducted to investigate the nature of the interaction between the drug and the surfactants. Several theoretical models (Clint, Rubingh, Rosen, and Motomura) based on pseudo‐phase approximation and regular solution theory were applied to calculate the micellar parameters, surface parameters and corresponding thermodynamic parameters of the CTZ + CPC/CPB mixed system. These parameters include the interaction parameter ( β ), activity coefficient ( f ), maximum surface excess concentration (Г ∞ ), the surface area occupied per amphiphile molecule ( A min ), and Gibbs free energy (∆ G ), aiming to elucidate the interactions and non‐ideal behavior between CTZ and CPC/CPB. Furthermore, ultraviolet–visible (UV–Vis) spectroscopy analysis confirmed strong interactions between the drug and the surfactants. The binding energy of the mixtures, the energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), the band gap, and the electron density difference were calculated using the DFT/B3LYP method. The computational results indicate mutual attraction between the two components, which is highly consistent with the experimental findings.