Absorption spectroscopy, conductivity, and surface tension measurements were carried out at 298 K to study the solubilization of poorly soluble drugs sulfamethoxazole (SMX) and trimethoprim (TMP) in Aerosol‐OT (AOT) micellar media. The binding constants of SMX and TMP to AOT micelles were determined by applying the Benesi–Hildebrand equation. A comparison of the binding constants indicates that the binding tendency of TMP with AOT micelles is higher than that of SMX. To better analyze the incorporation of drugs into anionic AOT micellar media, surface tension measurements were performed in the presence of SMX and TMP in aqueous media. The influence of TMP and SMX on the surface properties of AOT was determined using the Gibbs Adsorption Isotherm. Changes in the surface properties of AOT determined by surface tension measurements in the presence of drugs are in good agreement with the binding constants determined spectrophotometrically. Calculated surface parameters indicate higher incorporation of TMP with AOT than that of SMX. Comparison of the aqueous solubility of TMP and SMX with micellar media indicated solubility enhancements for both poorly soluble drugs. A special attempt was made to highlight simultaneous interactions of TMP and SMX with AOT using both surface tension and conductometric measurements that can be used to determine counterion‐binding parameters.

The aggregation behaviour of an amphiphilic antidepressant drug amitriptyline hydrochloride (AMT) has been studied to determine the micellar solution behaviour in the presence of polar (methanol and ethanol), dipolar aprotic solvents (acetone and 1,4 dioxane), salt (NaCl) and water structure-breakers (urea) at 298 K using electrical conductivity and surface tension measurements. From conductivity data, the ionization degree and counterion binding parameter of micelles have been determined. To better analyse influences of additives on micellar behaviour of AMT surface tension measurements were performed and surface properties of AMT i.e. maximum surface excess concentration and minimum area per surfactant molecule at the air/water interface were determined using Gibbs Adsorption Isotherm in the absence and presence of various amount of additives. Conductometric and surface tension measurements were successfully used in determination of critical micelle concentration (CMC) of AMT in aqueous media. The experimental results of AMT indicated that CMC values altered with the addition of additives. Micellization of AMT totally inhibited when methanol, ethanol, acetone, 1,4 dioxane and urea concentration reached a certain value while the CMC of AMT decreased with the increase in concentration of NaCl.