Interaction of biocompatible polymers with amphiphilic phenothiazine drug chlorpromazine hydrochloride

Interaction of chlorpromazine hydrochloride (CPZ), an amphiphilic drug of phenothiazine category, was investigated with several biocompatible polymers. The studies were carried out by using conductometry. Results were found to be in analogy with the surfactant-polymer interactions. The plots of specific conductivity versus concentration of drug were nonlinear with three different linear regions and with two clear breaks. First break point is regarded as the onset of aggregation, i.e., critical aggregation concentration (C-1) and appeared well below the critical micelle concentration of pure drug. Second break (C-2) is regarded as polymer saturation point which is akin to the critical micelle concentration. At C-2 polymer domain saturated with the drug monomers which occurred at quite higher concentration suggestive of unavailability of drug monomers at lower concentrations due to the polymer-drug binding. Free energies of aggregation (Delta G(agg)) and micellization (Delta G(mic)) were calculated with the help of degrees of micelle ionization obtained from the specific conductivity-[CPZ] plots. (C) 2012 Elsevier B.V. All rights reserved.