Thermodynamics of the amphiphilic drug, amitriptyline hydrochloride-surfactant/polymer systems at the cloud point

Abstract

Herein, we report the energetics of clouding in amphiphilic drug, amitriptyline hydrochloride (AMT-a tricyclic antidepressant drug), in the presense of surfactants and polymers. Surfactants/polymers are extensively used in drug delivery as drug carriers. The cloud point (CP) of an amphiphile can be considered as the limit of its solubility. The clouding components release their solvated water and separate out from the solution. Hence, the standard Gibbs free energy change of solubilization (ΔG⁰_s) is evaluated from the relation ΔG⁰_s=-RTlnX_s. For all the additives, ΔG⁰_s is found to be positive. However, ΔH⁰_s and TΔS⁰_s values are negative as well as positive depending upon the type and nature of the additive and the results are discussed on the basis of these factors.