Study of volumetric, viscometric, and aggregation properties of losartan potassium and its interaction with amino acids and cetyltrimethylammonium bromide in aqueous solution

This manuscript reports volumetric, viscometric, and aggregation properties of losartan potassium (LP) in aqueous medium and its interaction with a cationic surfactant (cetyltrimethylammonium bromide [CTAB]). Densities of drug solutions were used to calculate apparent molar volumes while constants of Jones–Dole equation were calculated from viscosity measurements. By measuring surface tension, refractive index, and electrical conductivity of drug solutions, critical micelle concentration (CMC) of drug was determined, and calculation of surface excess concentration, free energy change of adsorption, free energy change, entropy change, and enthalpy change of micellization was carried out. UV/Visible spectroscopic data were used to get an understanding about the interaction of drug with cationic surfactant (CTAB). This interaction gives an idea about the interaction of drug with biomembrane as micelles of surfactant are similar to membranes in structure. The data were also used to calculate different important parameters for drug–surfactant interaction such as partition coefficient and binding constant. Moreover, two amino acids (glycine and l‐tryptophan) were used in solutions of drug separately to change its CMC. The results from volumetric and viscometric studies showed that the presence of drug in solution resulted in more organization of solvent molecules due to hydrophobic interaction. From the values of ∆G°ads and ∆G°m, it was concluded that the adsorption of drug molecules at solution–air interface and formation of micelles occurred spontaneously. A strong drug‐surfactant (LP–CTAB) interaction was observed by the attachment of drug molecules onto micellar surface of surfactant. The presence of amino acids in the solution of drug caused a decrease in the CMC of LP.