Abstract
The phase behavior of cationic amphiphilic drug amitriptyline hydrochloride (AMT) under the influence of surfactants, polymers, cyclodextrin and fatty acids has been investigated. These additives are generally used in pharmaceutical industry as excipients for drug delivery systems. The degree of CP variation by different additives is different depending upon the type and structure of additive. Cationic (conventional/gemini) surfactants depict continuous increase whereas anionic surfactants show a maximum at a particular concentration. Polymer behavior in drug solution is prescribed by the number of monomer units present in a peculiar polymer. beta-cyclodextrin acts as a simple sugar therefore a decrease in CP of the drug solutions is observed. Fatty acid behavior is similar to anionic surfactants i.e. shows maximum at fixed concentration for particular types of fatty acid. The cloud point (CP) of AMT falls with an increase in pH because of deprotonation of the drug molecules. The thermodynamic parameters are evaluated: whereas Delta G(c)degrees is found to be negative, and depending upon the type and nature of additive Delta H-c degrees and T Delta S-c degrees values are negative as well as positive. (C) 2012 Elsevier B.V. All rights reserved.