Effect of porcine pancreatic α-amylase on dexamethasone release from aqueous solution containing natural γ-cyclodextrin.

Dexamethasone release from natural γ-cyclodextrin (γCD) complexes was investigated in presence of porcine pancreatic α-amylase (PPA). The phase-solubility of dexamethasone in aqueous γCD solutions was determined, PPA degradation of γCD was investigated, and permeation studies were performed in simulated tear fluid. The phase-solubility profile was of B type and the stability constant (K) of the dexamethasone/γCD complex determined from the initial linear section of the profile was relatively high or 12887 M. The high K value indicates that dexamethasone has high affinity for γCD under the test condition. From the PPA catalyzed γCD degradation studies the Michaelis-Menten constant (K) and V were determined to be 3.24 mM and 9.79 × 10 mM/min, respectively. The permeation studies performed at low γCD concentrations, showed that dexamethasone is released from the complex solutions at faster rate when PPA was present than when no PPA was present.