Studies of pectin HM/Eudragit RL/Eudragit NE film-coating formulations intended for colonic drug delivery

Theophylline pellets were coated with Eudragit NE30D aqueous dispersions, containing various pectin HM/Eudragit RL30D ionic complexes, using an Uni-Glatt fluidized-bed apparatus. Dissolution studies were then carried out on the coated pellets at pH 6.0, in absence and in presence of commercial pectinolytic enzymes. The theophylline release from the coated pellets, after an initial latency phase, occurred linearly as a function of time. The theophylline release rate was dependent on the pectin HM content of the complexes incorporated in the coatings. The lowest theophylline release from the coated pellets was obtained when the pectin HM content of the complexes was 20.0% w/w (related to Eudragit RL), i.e. when the complexation between pectin HM and Eudragit RL is optimal. The theophylline release from the coated pellets was slower in presence of the pectinolytic enzymes when the pectin content of complexes is higher than 20% w/w. On the other hand, the effect of the enzymes induced an increase of the theophylline release when the pectin HM content of the coatings ranged between 10.0 and 15.0% w/w (related to Eudragit RL).