Influence of β-cyclodextrin on the Properties of Norfloxacin Form A
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Cyclodextrins are able to form host–guest complexes with hydrophobic molecules to result in the formation of inclusion complexes. The complex formation between norfloxacin form A and β-cyclodextrin was studied by exploring its structure affinity relationship in an aqueous solution and in the solid state. Kneading, freeze-drying, and physical mixture methods were employed to prepare solid complexes of norfloxacin and β-cyclodextrin. The solubility of norfloxacin significantly increased upon complexation with β-cyclodextrin as demonstrated by a solubility isotherm of the AL type along with the results of an intrinsic dissolution study. The complexes were also characterized in the solid stated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffractometry, scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance (ssNMR) spectrometry. The thermal analysis showed that the thermal stability of the drug is enhanced in the presence of β-cyclodextrin. Finally, the microbiological studies showed that the complexes have better potency when compared with pure drug.
KEY WORDSbioassay complexation intrinsic dissolution norfloxacin β-cyclodextrin
The authors are grateful to PACD-FCFAr-UNESP (Araraquara-Brazil), FAPESP process no 2010/13335-2 (São Paulo-Brazil) and CNPQ (Brasília-Brazil) for the fellowships and União Química (Minas Gerais-Brazil) for the financial support. In addition, the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), the Secretaría de Ciencia y Técnica de la Universidad Nacional de Córdoba (SECyT-UNC), and Ministerio de Ciencia y Tecnología (MinCyT) de la Provincia de Córdoba are grateful for the financial support. We also thank Ferromet S.A. (agent of Roquette in Argentina) for their donation of β-cyclodextrin. The cooperation from colleagues at the School of Pharmacy, Virginia Commonwealth University (VCU) is also highly appreciated. We also are grateful to Professor Peter R. Byron from VCU for his help and guidance with the intrinsic dissolution study.
Conflicts of Interest
The authors have declared no conflict of interest.
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