Influence of additives (inorganic/organic) on the clouding behavior of amphiphilic drug solutions: Some thermodynamic studies

Herein we provide a detailed result about the effect of various additives, viz. inorganic salts, quaternary ammonium bromides (QABs) and amino acids on clouding behavior of amphiphilic drug amitriptyline hydrochloride (AMT). The continuous increase in the cloud point (CP) of drug by increase in inorganic salt concentration and the magnitude of increases rely upon the position of the salts in Hofmeister series and hydrated radii. The QABs also influence continuous increase in the CP, which is illustrated in terms of the alkyl chain length of peculiar QAB. The effect of amino acids on CP of the drug solution is dependent upon the characteristics (acidic, basic, polar or nonpolar) of particular amino acids. The overall behavior of additives has been analyzed and discussed on the basis of electrostatic repulsion or interaction, micellar growth, and mixed micelle formation between the ingredients. In addition to this, thermodynamic parameters are also evaluated.