Tensiometric and conductometric studies of the effect of polymers on the aggregation behavior of cationic amphiphilic drugs IMP and PMT

The present work is aimed at studying the interactions of two cationic amphiphilic drugs, viz. imipramine hydrochloride (IMP) and promethazine hydrochloride (PMT), with several polymers (cationic, nonionic, and anionic) in aqueous solutions by Using tensiometric and conductivity measurements. The onset of interaction, the so-called critical aggregation concentration (CAC), decreases on increasing the polymer concentrations whereas the critical micelle concentration (CMC) of the drugs rises. The strength of interaction was found to be dependent upon the nature of the polymers. The interaction between the anionic polymer NaCMC and drugs was maximum while it was minimum in case of drug-cationic polymer HECEQsystem. The interfacial parameters like Gibbs surface excess (T-max) and the minimum area occupied by the drug monomer (Amin) have been estimated. The free energies of adsorption (Delta G(ad)(0)), aggregation (Delta G(a)(0)), micellization (Delta G(m)(0)) and transfer (Delta G(t)(0)) associated with the interactions between the drugs and polymers have also been evaluated. (C) 2013 Published by Elsevier B.V.