Interaction of cefalexin monohydrate with cetyldimethylethylammonium bromide

A study of the interaction of cefalexine monohydrate (CLM) with Cetyldimethylethylammonium Bromide (CDMEAB) has been carried out by conductance measurements in aqueous medium and in aqueous solution of salts over temperature range of 303.15 K to 318.15 K. From conductivity versus surfactant concentration plots, two critical micelle concentrations c1∗ and c2∗ were obtained for both CDMEAB and CLM–CDMEAB systems in all the cases. The changes of c∗   values of CDMEAB in the presence of CLM is indicative of the interaction between CLM and CDMEAB. For the CLM–CDMEAB system, the values of c1∗ are lower and c2∗ values are higher in magnitude compared to that of pure CDMEAB in water over the range in temperature studied. In aqueous solutions of KCl and K2SO4, the decrease of c∗ values indicates the favour of micellization of CLM–CDMEAB system. The ΔG0m values are negative and the spontaneity of micellization process is found to increase with increase of temperature. The values of ΔH01,m and ΔS01,m indicate that the drug mediated CDMEAB aggregation is both enthalpy and entropy controlled while ΔH02,m and ΔS02,m values indicate entropy driven micellization. The results indicate that binding interactions between CLM and CDMEAB are both electrostatic and hydrophobic in nature while the contribution of hydrophobic interaction is dominant at higher temperature. The linear correlation between ΔH0m and ΔS0m values is observed in all cases.

► We examine the effect of cefalexine monohydrate on the micellization of CDMEAB.
► The critical micelle concentrations of CDMEAB in presence of drug are changed.
► Electrostatic and hydrophobic interactions between CLM and CDMEAB are proposed.
► KCl and K2SO4 favour the micellization of CLM–CDMEAB system.