Effect of electrolytes on the cloud point of chlorpromazine hydrochloride solutions

Clouding phenomenon in amphiphilic systems: A review of five decades

Phase separation in amphiphilic systems is an important phenomenon. The temperature at which an amphiphilic solution phase separates is known as Cloud Point (CP). This article reviews in detail the process of phase separation in various amphiphiles (surfactants, polymers and drugs) and effect of different classes of additives on the CP of these amphiphilic systems. Ions affect the CP of drugs in a different way: kosmotropes and hard bases decrease while chaotropes and soft bases increase the CP of nonionic and cationic surfactants. Anionic surfactants show CP in presence of quaternary salts only. Thus, depending upon the nature and concentration of additive, the CP of an amphiphilic system gets increased or decreased and, hence, properties of the system may be tuned as per the need and use. A system with CP at high concentration can be made to phase separate at lower concentration by simply introducing an appropriate additive in it. This makes the system cost effective. On the other hand, if not required, a low CP can be enhanced with the help of another type of a suitable additive.

Clouding behavior of antidepressant drug–additive system in ethylene glycol/glycerol–water mixed media and their thermodynamic parameters at cloud point

The influence of ethylene glycol (EG)/glycerol(GL)–water mixed media on clouding action of an amphiphilic drug, amitriptyline hydrochloride was studied in presence and absence of inorganic salts in selected compositions of EG–WR and GL–WR mixed media.

Phase Separation Study of a Surface-Active Drug, Promazine Hydrochloride, in Presence of Surfactants and Ureas

As clouding in drugs causes high concentration of drug at a particular site which may prove harmful to the body, the clouding behaviour of a tricyclic phenothiazine drug promazine hydrochloride (PMZ) in aqueous solutions has been studied in the presence of surfactants and ureas. The cloud point (CP) decreases with increase in pH due to deprotonation of the drug molecules. Addition of non-ionic and cationic (conventional as well as Gemini) surfactants increased the CP whereas anionic surfactants showed a peaked profile. The urea family additives influenced the CP in both ways that depended whether they contain >C=O or >C=S moiety: the former interacts with the micelles and lowers the CP while the latter (due to its electropositive character) may not interact and hence CP increases. Dye solubilization results indicate micellar growth with the addition of surfactants in PMZ solutions. The results are interpreted taking cognizance of mixed micelle formation, hydrophobic interactions, and/or change in solvent structure.