Influence of processing parameters and formulation factors on the drug release from tablets powder-coated with Eudragit® L 100-55

The aim of this study was to develop a dry powder coating process for chlorpheniramine maleate (CPM) tablets using Eudragit (R) L 100-55 as the delayed release polymer. Powder coating, a water and organic solvent-free process, was investigated as a method to prevent the migration of an ionizable, highly water soluble model drug into the polymeric film during the coating process. Eudragit (R) L 100-55 was pre-plasticized with triethyl citrate (TEC) using hot-melt extrusion at levels of 20%, 30%, and 40%, based on the polymer weight. The extrudate was subsequently cut into pellets and cryogenically ground into a fine powder. Talc was incorporated into the coating powder as an anti-tack agent. PEG 3350 was used as a primer for the powder coating of tablets with pre-plasticized Eudragit (R) L 100-55. The addition of polyethylene glycol 3350 (PEG 3350) to the pre-plasticized Eudragit (R) L 100-55 was necessary to enhance the adhesion of the coating powder to the tablet cores. PEG 3350 also improved film formation and coalescence of the polymeric particles due to its plasticization effects on the acrylic polymer. For comparison, theophylline tablets were also coated with pre-plasticized Eudragit (R) L 100-55. Theophylline was selected as a less water soluble model drug. The powder coating process was performed in a modified laboratory scale spheronizer. The drug release rate was dependent both on TEC content and the coating level. The stability of the powder-coated CPM tablets was confirmed at 25 degrees C/60% RH over a storage time of 12 weeks. (c) 2007 Elsevier B.V. All rights reserved.