Abstract
The objectives of this study were to evaluate the mechanical and thermal properties of films prepared from Eudragit (R) NE 30D/Eudragit (R) L 30D-55 blends and to examine the dissolution behavior of beads coated with the polymer blends up to 120% weight gain. Eudragit (R) NE 30D and L 30D-55 dispersions were blended at 50:50, 67:33, 75:25, and 80:20 ratios. Cast films were evaluated by texture analysis and differential scanning calorimetry. Increasing Eudragit (R) NE 30D concentration increased miscibility, softness, and decreased stiffness of the films. At 80:20 ratio, the polymer blend was completely miscible whereby Eudragit (R) L 30D-55 was molecularly distributed in the mixture. This was confirmed by SEM analysis. The surface morphology of films and beads was evaluated before and after dissolution by scanning electron microscopy. SEM analysis demonstrated that the size of the pores formed after the dissolution of Eudragit (R) L 30D-55 at pH 6.8 was dependent on the miscibility of the Eudragit (R) blend. The implications of this effect were apparent in dissolution studies. For the 75:25 and 80:20 blends, a linear increase in lag time up to 7 h was observed with an increase in coat weight gain from 15 to 120%. At 60% weight gain, the 80:20 blend delayed drug release by approximately 7 It whereas the less miscible 75:25 blend delayed drug release by only 3.5 h. A lag time could therefore be controlled by manipulating both the theoretical weight gain of the beads and the concentration of Eudragit (R) NE 30D in the blend. (c) 2008 Elsevier B.V. All rights reserved.