Micellization and clouding phenomenon of amphiphilic antidepressant drug amitriptyline hydrochloride: Effect of KCl

In the present study, we report the micellization and clouding behavior of an amphiphilic antidepressant drug viz., amitriptyline hydrochloride (AMT) at different fixed temperatures and KCl concentrations in aqueous solutions. The critical micelle concentration (cmc) of AMT, as measured by conductivity method, increases with increasing temperature and decreasing with KCl concentration. The thermodynamic parameters viz., standard Gibbs energy (Delta G(m)(0)), standard enthalpy (Delta H-m(0)), and standard entropy (Delta S-m(0)) of micellization of AMT are evaluated. The values clearly indicate more stability of the AMT solution in presence of KCl. Like surfactant, AMT also shows phase separation behavior. The cloud point (CP) of AMT in water decreases with increase in pH of the medium because of the deprotonation of the drug molecule. The CP values increase with increasing KCl concentration and AMT concentrations, clearly indicating the micellar growth at higher concentration. Furthermore, for better understanding of the behavior of drug molecule in water, we evaluated various thermodynamic parameters of the above drug molecule at CP. (C) 2011 Elsevier B.V. All rights reserved.