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Inclusion Complexes of Piroxicam with ß-Cyclodextrin Derivatives in Comparison with the Natural ß-Cyclodextrin

1st Communication: Preparation and physicochemical characterization

Seham A. Elkheshen*), Sayed M. Ahmed, Omima A. Sammour, and Bushra T. Al-Quadeib

Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh (Saudi Arabia)

*) Current address: see address for correspondence

Two modified cyclodextrins (CD), heptakis-[2,6-di-O-methyl]-ß-cyclodextrin (DM-ß-CD) and hydroxypropyl-ß-cyclodextrin (HP-ß-CD), were adopted for preparing piroxicam-cyclodextrin (PIR-CD) inclusion complexes, in comparison with ß-cyclodextrin (ß-CD). Inclusion complexes were prepared via co-precipitation and freeze drying techniques in a 1 : 1 and 1 : 2.5 molar ratio (drug-to-CD). The physicochemical characteristics of PIR-CD inclusion complexes were evaluated using differential scanning calorimetric analysis (DSC), X-ray diffraction analysis (XRD) and Fourier transform infrared analysis (FTIR). Results were compared with the pure drug and the corresponding physical mixtures (PM) in the same molar ratios. Phase solubility diagrams of PIR with each of the CDs in distilled water at 37 ± 0.5 °C, indicated the formation of soluble complexes of the A_L type.
The apparent stability constant, which reflect the affinity of CD to the drug, can be arranged in the following order: DM-ß-CD > H P- ß-CD > ß-CD. No interaction of the drug with CD was observed in the PMs as proven by the DSC, XRD and FTIR analysis. The persistence of some of the characteristic peaks of piroxicam (CAS 36322-90-4) in the XRD patterns of coprecipitates indicated partial inclusion of the drug in the CD cavities. DSC and XRD clearly indicated the formation of an amorphous powder with freeze dried products. The FTIR spectral changes indicated the inclusion of piroxicam within the CD cavities.

Key words CAS 36322-90-4 · Complexation · ß-Cyclodextrin, derivatives · Inclusion complexes · Piroxicam