title: Determination of the free/included piroxicam ratio in cyclodextrin complexes: comparison between UV spectrophotometry and differential scanning calorimetry.
abstract: Few analytical techniques allow to evaluate the inclusion yield of cyclodextrin-drug complexes, because most manufacturing processes give amorphous products. In this study, we have developed an alternative method to differential scanning calorimetry, to accurately determine the free/complexed piroxicam ratio by UV spectroscopy. This method is based on the differential solubility of the piroxicam-beta-cyclodextrin 1:2.5 mol/mol complex in water-acetonitrile (1:1, v/v) (Solvent A) or in anhydrous acetonitrile (Solvent B), both containing 0.05 M HCl. In anhydrous acetonitrile, beta-cyclodextrin is insoluble and the included drug remains entrapped, allowing the free piroxicam determination, while with 50% of water, the complex is totally dissolved, allowing the determination of the total guest content. This method was validated for linearity, precision and accuracy. The presence of cyclodextrin does not influence the assays, but more than 0.5% of water in Solvent B significantly affects the determination of the free piroxicam content. In comparison with differential scanning calorimetry, both detectability and precision were improved. It is now possible to analyse complexes with an inclusion purity greater than 99%.
authors: Department of Pharmaceutical Technology, Institute of Pharmacy, University of Liege, CHU, tour no. 4, Avenue de l'Hôpital, 1, Belgium. t.vhees@ulg.ac.be
authors: Thierry
authors: T
authors: Van Hees
authors: Geraldine
authors: G
authors: Piel
authors: Sandrine Henry
authors: SH
authors: de Hassonville
authors: Brigitte
authors: B
authors: Evrard
authors: Luc
authors: L
authors: Delattre
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000032:analysis*; D002152:Calorimetry, Differential Scanning; D003505:Cyclodextrins / Q000737:chemistry; D010894:Piroxicam / Q000032:analysis*; D015203:Reproducibility of Results; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D003505:Cyclodextrins; D010894:Piroxicam