Phase behavior study of amphiphilic drugs: effect of pharmaceutical excipients.

Effect of various additives, like conventional as well as gemini cationic surfactants, non-ionic surfactants, hydrotropes, bile salts, fatty acid salts and β-cyclodextrin on the cloud point (CP) of two amphiphilic drugs promethazine (PMT) and promazine (PMZ) hydrochlorides was investigated. These additives are generally used as pharmaceutical excipients. The CP variation with the additive concentration has been determined and the energetic parameters of the process have been estimated. All the surfactants increase the CP, while hydrotropes, bile salts and fatty acid salts, when added in low concentrations, increase or decrease, depending the added concentration, increase or decrease the CP. β-cyclodextrin is found to decrease the CP of the drug solutions.