Encapsulation of nabumetone by means of -drug:: (β-cyclodextrin)2:polyvinylpyrrolidone ternary complex formation

The aim of the present study was to investigate the effect of the presence of the water-soluble polymer polyvinylpyrrolidone (PVP) MW = 24,000 g/mol, on the complexing of the anti-inflammatory drug nabumetone, with beta-cyclodextrin (beta-CD). The data show that the polymer interacts with the free nabumetone and with the nabumetone: beta-CD inclusion complex, in both cases with a stoichiometry of 1:1. The interaction constants are 1.3 x 10(4) M-1 and 1.6 x 10(4) M-1, respectively. The presence of PVP, changes the drug:cyclodextrin interaction, a nabumetone:(beta-CD)(2):PVP complex being formed. In addition, the presence of PVP, produces a strong increase in the global binding constant, beta(2) = (22.12 +/- 0.22) x 10(6)M(-2) at 1% PVP. In the ternary complex, the nabumetone is wrapped at both ends for the beta-CD. In this complex the polymer seems to act as a bridge between both beta-CD molecules that bind the nabumetone. (c) 2006 Elsevier B.V. All rights reserved.