Influence of External factors on Self-Aggregation of Amphiphilic Antidepressant Drug: A Thermodynamic Study

Apparent molar volumes, (V phi adiabatic compressibilities, (K phi and thermal expansivities (E0) of venlafaxine hydrochloride, an amphiphilic antidepressant drug, have been determined in water and aqueous 0.01 mol/kg CaCl/sub 2/ 2H/sub 2/O solutions. The densities and ultrasound velocities were measured at 298.15 and 303.15 K by using an Anton Paar density sound analyzer (DSA 5000M). The critical micelle concentrations (cmc) of this drug were obtained from ultrasound velocity (u) measurement by using recently developed least square fitting algorithm. Negative deviations from Debye-Huckel limiting law of apparent molar volume for this drug was obtained at 298.15 and 303.15 K in water and 0.01 mol/kg CaCl/sub 2/ 2H/sub 2/O solutions showing no pre-association below the critical micellar concentration. The volumetric parameters indicating the interactions of venlafaxine hydrochloride with CaCl/sub 2/ 2H/sub 2/2O and in water have been obtained by using transfer molar volume and the resulting values are in good agreement within each other within experimental error. The Partial molar expansivity, (E0), and second derivative values, have also been estimated. (author)