Hydroxypropyl methylcellulose microspheres with piroxicam and piroxicam-hydroxypropyl-beta-cyclodextrin inclusion complex.

Inclusion complexation between piroxicam (PX) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) in the presence of hydroxypropyl methylcellulose (HPMC) was studied in aqueous solution and in the solid state. Phase solubility studies were used to evaluate the HPbetaCD complexation in the presence of HPMC. Stability constants, Ks, of the complexes were determined. The stability of the inclusion complex was improved in the presence of HPMC. Solid microspheres were obtained by spray drying, and were characterized by differential scanning calorimetry (DSC), regarding drug content, and particle size distribution. Scanning electron microscopy (SEM) was also used to characterize the systems prepared. In the solid system HPMC facilitated to some extent the drug dissolution due to increased solubility. The presence of HPMC and HPbetaCD in the microspheres promoted dissolution rate. Cyclodextrin complexation increased PX flux through a semipermeable membrane. Presence of HPMC in the system additionally increased the drug flux more than 80%, by increasing the drug solubility and consequently the affinity of the ternary complex for the aqueous diffusion layer in the donor compartment.