Abstract
The purpose of this study was to determine the cloud point of an amphiphilic drug and to search for means to boost or suppress the cloud point, used in pharmaceutical formulations. Organic compounds (amino acids, saccharides, alcohols, surfactants, and polymers), which are used as pharmaceutical excipients, were tested to demonstrate their effect on the cloud point of the amphilphilic drug promethazine hydrochloride (PMT). A number of compounds raised the cloud point of the drug. These excipients can be classified as ionic and nonionic cloud-point boosters (CPBs). The nonionic CPBs include high molecular weight poly(ethylene glycols), poly(oxyethylene cetyl ethers), whereas ionic CPBs are cetylpyridinium chloride (CPC), cetylpyridinium bromide (CPB), cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylammonium bromide (DTAB), 14-s-14 (s = 4, 5, 6), and 16-s-16 (s = 4, 6). The cloud-point suppressers include saccharides (sugars), amino acids, and alcohols. The extent of cloud-point (T-CP) variation by different excipients is different (dependent on the nature and structure). The thermodynamic parameters are evaluated: whereas Delta G(c)degrees is found to be negative, Delta H-c degrees and T Delta S-c degrees values are negative as well as positive (depending upon the type and nature of the additive).