Abstract
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 Bs type and the stability constant (K1:1) of the dexamethasone/γCD complex determined from the initial linear section of the profile was relatively high or 12887M-1. The high K1:1 value indicates that dexamethasone has high affinity for γCD under the test condition. From the PPA catalyzed γCD degradation studies the Michaelis-Menten constant (Km) and Vmax were determined to be 3.24mM and 9.79×10-3 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.
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