Solubility enhancement of simvastatin and atorvastatin by arginine: A solvodynamics study

Abstract

Arginine (ARG) aided solubility enhancement of statin-based model drugs such as simvastatin (SMV) and atorvastatin (ATV) has been reported. Herein, both SMV and ATV are considered as a solute, whereas ARG the cosolute. The present study deals with experiments to illustrate the solute-solvent interaction, solute-cosolute interaction and the thermodynamic parameters during the solubilisation of the above drug candidates in water in the presence of ARG. The soundspeed values of ARG, Simvastatin-Arginine (SMV-ARG) and Atorvastatin-Arginine (ATV-ARG) systems were determined in water maintaining different concentrations (0.01, 0.02, 0.04, 0.09, 0.18, 0.36 and 0.73moldm−3) of aqueous ARG, with saturated presence of SMV (SMV-ARG) and ATV (ATV-ARG) at 298.15K. Values of refractive index of the above system were recorded at 298.25, 303.15, 308.15, and 313.15K. Refractive index values were used to calculate the molar refractivity and the results discussed accordingly. Values of sound speed were used to evaluate acoustic parameters such as isentropic compressibility (Ks), apparent isentropic molar compressibility (Ksϕ), relative association (Ra), acoustic impedance (Z), internal pressure (πi), and free volume (Vf). It was observed that sound velocity increased with the increase in case of ARG concentration with linear fashion (R2=0.9978). Compressibility values decreased with increase in ARG concentration. Changers in acoustic parameters were discussed in terms of solute-solvent interaction and structural effects of water for all systems.