Study of the cloud point variation of amitriptyline hydrochloride solutions in presence of amines and amino acids

In this paper clouding phenomenon in aqueous solutions of an amphiphilic drug amitriptyline hydrochloride is reported. The effect of adding ethylamine, butylamine, hexylamine, heptylamine, octylamine, ethylenediamine, diethylenetriamine, tetraethylenepentramine, aniline, and benzylamine on the cloud point of solutions containing a fixed drug concentration (50 mM) was seen. All the amines decrease the cloud point by intercalating between the head groups with protonated amine groups at the micellar surface. The amino acids used (lysine, arginine, histidine) also behave similarly. The results are discussed in the light of a particular additive’s ability to remove water from the head group region of the drug micelles.