Thermodynamics at the Cloud Point of Phenothiazine Drug Chlorpromazine Hydrochloride-Additive Systems

An amphiphilic drug chlorpromazine hychochloride (CPZ), a phenothrazine with neuroleptic activity, undergoes clouding phenomena, which depend upon the physicochemical conditions (e g, concentration, pH, temperature, etc). The clouding components release their solvated water and separate out from the solution. Therefore, the cloud point (CP) of an amphiphile can be considered as the limit of its solubility. Herein, we report the energetics of clouding in CPZ in the presence of additives (viz., alcohols, surfactants, and polymers). The standard Gibbs energy change of solubilization (Delta G(s)(0)) for all of the additives is found to be positive However, the standard enthalpy change (Delta H-s(0)) and the product of the temperature and the standard entropy change (T Delta S-s(0)) values are negative as well as positive, depending upon the type and nature of the additive. mid the results me discussed on the. basis of these factors