Influence of Fumed Silicon Dioxide on the Stabilization of Eudragit®RS/RL 30 D Film-Coated Theophylline Pellets

Abstract

The objective of this study was to investigate the influence of various grades of fumed silicon dioxide on the drug release rate and physical aging of theophylline pellets coated with Eudragit® RS 30 D and RL 30 D. Free films were assessed for both physicomechanical properties and water vapor permeability with respect to time and storage conditions. The release rate of theophylline was influenced by the physical properties of the silicon dioxide employed. As the particle size of the silica dioxide decreased, there was an increase in dispersion viscosity, as well as a decrease in the theophylline release rate from the coated pellets. Films prepared from formulas containing Aeroperl® 300 had twice the water vapor transmission rate of films prepared from formulas containing Aerosil® 200 VV and Cab-O-Sil® M-5P and showed consistent moisture permeability values during storage for up to 1 month at 25°C/0% relative humidity (RH). Scanning electron microscopy (SEM) imaging of pellets coated with a formulation containing Aerosil® 200 VV or Cab-O-Sil® M-5P demonstrated film structures that were homogenous, while those coated with a formulation containing Aeroperl® 300 produced heterogeneous films with large particles of the excipient present within the polymeric matrix of the film. Stability in the drug release rate exhibited by pellets coated with a formulation containing Eudragit® RS 30 D, 15% triethyl citrate (TEC), and 30% Aeroperl® 300 was attributed to the stabilization of the moisture vapor transmission rate of the acrylic films. Increasing the concentration of Aeroperl® 300 in the coating formulation increased the theophylline release rate from coated pellets.