The inclusion behavior of natural cyclodextrins (CDs) and polymers based on natural cyclodextrins (CD-polymer), in solution and in solid-state, was studied towards a poorly water-soluble anti-helminthic drug, albendazole (ABZ), chemically methyl[5-(propylthio)-1-H-benzimidazol-2yl]carbamate. Drug-cyclodextrin solid systems were prepared by freeze-drying. Phase solubility study was used to evaluate the interaction in solution, between ABZ/(CDs) and ABZ/CD-polymers. The stability constants of ABZ/natural CDs and ABZ/CD-polymers complexes were calculated by phase solubility method. The apparent solubility of Albendazole was enhanced especially with poly alpha-CD. The formation of inclusion complexes with natural CDs and polymers of cyclodextrin in the solid-state form were confirmed by Fourier Fransform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR).
This contribution focused on the solubility improvement of the poorly water-soluble steroid hormone progesterone which, in its natural state, presents a reduced oral bioavailability. In the first part of this study, two simple, reproducible methods that were candidates for use in the preparation of inclusion complexes with cyclodextrins were investigated. Solubility capacities of the progesterone complex with hydroxypropyl-beta-CD (HPbeta-CD), hydoxypropyl-gamma-CD (HPgamma-CD), permethyl-beta-CD (PMbeta-CD), and sulfobutylether-beta-CD (SBEbeta-CD), prepared by the freeze-drying and precipitation methods, were evaluated by Higuchi phase solubility studies. The results showed that HPbeta-CD and PMbeta-CD were the most efficient among the four cyclodextrins for the solubilization of progesterone, with the highest apparent stability constants. Therefore, dissolution studies were conducted on these latest progesterone/cyclodextrin complexes and physical mixtures. Two additional natural cyclodextrins, beta-CD and gamma-CD, were taken as references. Hence, the influence of more highly soluble derivatives of beta-CD (HPbeta-CD, PMbeta-CD) on the progesterone dissolution rate, in comparison to pristine beta-CD, alongside an increase in the cavity width for gamma-CD versus beta-CD, were investigated. The dissolution kinetics of progesterone dissolved from HPbeta-CD, PMbeta-CD, and gamma-CD revealed higher constant rates in comparison to beta-CD. Therefore, the aim of the second part of this study was to investigate the possibility of improving the dissolution rate of progesterone/beta-CD binary systems upon formation of ternary complexes with the hydrophilic polymer, PEG 6000, as beta-CD had the smallest progesterone solubility and dissolution capacity among the four cyclodextrins studied (beta-CD, HPbeta-CD, HPgamma-CD and PMbeta-CD). The results indicated that dissolution constant rates were considerably enhanced for the 5% and 10% progesterone/beta-CD complexes in PEG 6000. The interaction of progesterone with the cyclodextrins of interest on the form of the binary physical mixtures, complexes, or ternary complexes were investigated by differential scanning calorimetry (DSC) and Fourier transformed-infrared spectroscopy (FT-IR). The results proved that progesterone was diffused into the cyclodextrin cavity, replacing the water molecules and, in case of ternary systems, that the progesterone beta-cyclodextrin was well dispersed into PEG, thus improving progesterone bioavailability for subsequent oral delivery in the same way as derivatized cyclodextrins. The present work proves that ternary complexes are promising systems for drug encapsulation.
The object of this work is to investigate physicochemical characteristics and inclusion behavior of binary systems based on cyclodextrin polymer (Poly-CD) or native cyclodextrins (CDs) with a poorly water-soluble, nonsteroidal anti-inflammatory drug, nimesulide (NIM) chemically, N-(4-nitro-2-phenoxyphenyl)methanesulfonamide. Our formulations were studied in solution and solid-state. Drug-cyclodextrin solid binary systems were prepared by the freezedrying method. Phase solubility study was used to evaluate the interaction in solution, between NIM/CDs and NIM/(Poly-CD). The stability constants of NIM/CDs and NIM/(Poly-CD) complexes were calculated using the phase solubility method. The apparent solubility of NIM was enhanced especially with Poly--CD (up to78-fold) in neutral aqueous solutions without any organic solvents or surfactants. Copmlexes formation was confirmed, in the solid state, by differential scanning calorimetry, infrared spectroscopy and DRX. Complexation spontaneity of drug with cyclodextrin polymers was highlighted using G° values.
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