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

Apparent molar volumes, (V adiabatic compressibilities, (Kand thermal expansivities (E0) of venlafaxine hydrochloride, an amphiphilic antidepressant drug, have been determined in water and aqueous 0.01 mol/kg CaCl2.2H2O 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 CaCl2.2H2O solutions showing no pre-association below the critical micellar concentration. The volumetric parameters indicating the interactions of venlafaxine hydrochloride with CaCl2.2H2O 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, (∂2V0/∂T2), have also been estimated.

MUHAMMAD ASGHAR JAMAL, IFTIKHAR HUSSAIN BUKHARI, MAJID MUNEER AND KHURRAM SHAHZAD