β-Cyclodextrin-promazine hydrochloride interaction: Conductometric and viscometric studies

Herein we have studied the interaction of β-cyclodextrin (β-CD) with the amphiphilic drug promazine hydrochloride (PMZ) by using conductimetry and viscometry. From the observed results it was concluded that critical micelle concentration (cmc) of the pure drug was lower than the apparent critical micelle concentration (cmc∗) of the drug in the presence of β-CD. The cmc∗ increased on increasing the concentration of β-CD due to the encapsulation of the amphiphilic drug to the hydrophobic cavities of the β-CD which delayed the micelle formation. Viscosity of the solution decreased drastically on the addition of β-CD which further increased on increasing the drug solution. Free energies of micellization (ΔGmic) were calculated with the help of degrees of micelle ionization and cmc obtained from the specific conductivity−[PMZ] plots. Micellization was found to be less spontaneous in the presence of cyclodextrin.