Diclofenac/N-(2-hydroxyethyl)pyrrolidine : a new salt for an old drug

Twenty-four diclofenac salts were prepared using inorganic and organic, linear and cyclic, hydrophilic and hydrophobic bases and their behaviour in polar and poorly polar solvents was examined. Most salts were found more soluble in 1-octanol than in water, suggesting afair hydrophobicity of these compounds and their existence as ion pairs in non-polar sovents. The salt diclofenac/N-(2-hydroxyethyl)pyrrolidine (DHEP) is the most soluble of this group in 1-octanol (8.39% w/w) and in water (1.89% w/w), where it displays a surfactant behaviour above 1.44% w/w, which can be considered as a critical micellar concentration