title: Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug.
abstract: The aim of the study was to investigate the solubility of piroxicam (Prx) depending on the inclusion complexation with various cyclodextrins (CDs) and on ethanol as a co-solvent. The phase-solubility method was applied to determine drug solubility in binary and ternary systems. The results showed that in systems consisting of the drug dissolved in ethanol-water mixtures, the drug solubility increased exponentially with a rising concentration of ethanol. The phase solubility measurements of the drug in aqueous solutions of CDs, β-CD and γ-CD exhibited diagrams of AL-type, whereas 2,6-dimethyl-β-CD revealed AP-type. The destabilizing effect of ethanol as a co-solvent was observed for all complexes regardless of the CD type, as a consequence of it the lowering of the complex formation constants. In systems with a higher concentration of ethanol, the drug solubility was increased in opposition to the decreasing complex formation constants. According to this study, the type of CDs played a more important role on the solubility of Prx, and the use of ethanol as a co-solvent exhibited no synergistic effect on the improvement of Prx solubility. The Prx solubility was increased again due to the better solubility in ethanol.
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mail 50200, Thailand. suporn.charumanee@cmu.ac.th.
authors.forename: Suporn
authors.initials: S
authors.lastname: Charumanee
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mail 50200, Thailand. siriporn.okonogi@cmu.ac.th.
authors.forename: Siriporn
authors.initials: S
authors.lastname: Okonogi
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mail 50200, Thailand. jakkapan.s@cmu.ac.th.
authors.forename: Jakkapan
authors.initials: J
authors.lastname: Sirithunyalug
authors.affiliation: Department of Pharmaceutical Technology and Biopharmaceutics, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, Vienna 1090, Austria. karl.peter.wolschann@univie.ac.at.
authors.forename: Peter
authors.initials: P
authors.lastname: Wolschann
authors.affiliation: Department of Pharmaceutical Technology and Biopharmaceutics, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, Vienna 1090, Austria. helmut.viernstein@univie.ac.at.
authors.forename: Helmut
authors.initials: H
authors.lastname: Viernstein
keywords: co-solubilization; co-solvent; cyclodextrins; inclusion complexation; piroxicam