Effect of inorganic salts on the clouding behavior of hydroxypropyl methyl cellulose in presence of amphiphilic drugs

In this paper we report the effect of two cationic (imipramine hydrochloride (IMP) and promazine hydrochloride (PMZ)) and one anionic (sodium salt of ibuprofen (IBF)) drugs on the clouding behavior of a nonionic polymer hydroxypropyl methyl cellulose (HPMC). Though all the three drugs increase the cloud point (CP) of HPMC, the effect was found to be minimum in the case of IBF. Further, the effect of adding salts (NaF, NaCl, NaBr, NaNO3, Na2SO4, Na3PO4, KCl, KBr, KNO3) in the presence of amphiphilic drugs (IMP and PMZ) on the CP of HPMC was seen. Almost linear decrease in the CP was observed with the [salt] at fixed concentrations of these drugs whereas in the absence of drugs the decrement in the CP was slight. The energetic parameters (Delta G(c)(0), Delta H-c(0) and T Delta S-c(0)) were evaluated and it implies that the disruption of water structure becomes significantly prominent at lower concentrations of the drugs at fixed salt concentrations. (C) 2012 Elsevier B.V. All rights reserved.