| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 231212 | The Journal of Supercritical Fluids | 2011 | 8 Pages |
The complexation of piroxicam and 2-hydroxypropyl-β-cyclodextrin by means of supercritical CO2 has been investigated. The experiments were carried out by varying the temperature, pressure and contact time and introducing two different auxiliary agents: polyvinyl pyrrolidone or l-lysine.Cyclodextrins, which are widely used to solubilize a large variety of poorly soluble drugs, are often used in combination with some auxiliary agents to enhance the complexation efficiency of the conventional techniques. While many recent literature works report that supercritical carbon dioxide is a clean, non-toxic alternative to organic solvents, the use of auxiliary agents in the supercritical complexation process has been scarcely examined and still needs to be investigated.The inclusion complexes obtained in this work were analysed by means of the ‘differential solubility method’, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the supercritical treatment could be successfully employed below 140–150 °C without incurring thermal degradation of the samples. While 66% inclusion efficiency could be obtained at 140 °C and 30 MPa for a mixture of piroxicam/2-hydroxypropyl-β-cyclodextrin (1:2 molar ratio), higher percentages of complexation (95% in the ternary samples with polyvinyl pyrrolidone and 89–91% in those with l-lysine) could be obtained at a lower temperature (130 °C) when auxiliary agents were employed.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Auxiliary agents are scarcely studied in supercritical cyclodextrin complexation. ► 66% is maximum inclusion efficiency without auxiliary agents at 140 °C. ► It increases to 95% with PVP and to 89–91% with the l-lysine at 130 °C. ► Above 130–140 °C all types of complexes encounter thermal degradation. ► When PVP is used the amount of cyclodextrin in the formulation can also be halved.
