Physicochemical investigation of the effects of water-soluble polymers on vinpocetine complexation with β-cyclodextrin and its sulfobutyl ether derivative in solution and solid state

The studies reported in this work aimed to elucidate the inclusion complex formation of vinpocetine (VP), a poorly water-soluble base type drug, with beta-cyclodextrin (betaCD) and its sulfobutyl ether derivative (sulfobutyl ether beta-cyclodextrin (SBEbetaCD)), with or without water-soluble polymers (PVP and HPMC), by thoroughly investigating their interactions in solution and solid state. Phase solubility studies were carried out to evaluate the solubilizing power of both cyclodextrins (CDs), in association with water-soluble polymers, towards VP and to determine the apparent stability constants (K-c) of the complexes. SBEbetaCD showed higher solubilizing efficacy toward VP than the parent betaCD due to its greater solubility and complexing abilities, what was reflected in higher K-c values. Improvement in K-c values for ternary complexes clearly proves the benefit on the addition of water-soluble polymers to promote higher complexation efficiency. VP-CDs (1: 1) binary and ternary systems were prepared by physical mixing, kneading, co-evaporation, and lyophilization methods. In the solid state, drug-carrier interactions were studied by scanning electron microscopy (SEM), differential scanning calorimerry (DSC), X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy. The results of these analysis suggested the formation of new solid phases, some of them in amorphous state, allowing to the conclusion of strong evidences of binary and ternary inclusion complex formation between VP, CD and water-soluble polymers, particularly for co-evaporated and lyophilized binary and ternary products. (C) 2003 Elsevier B.V. All rights reserved.