Properties of theophylline tablets powder-coated with methacrylate ester copolymers

The purpose of this paper is to characterize the physiochemical and dissolution properties of tablets coated using a novel, solvent-free powder coating process. The ammonio methacrylate copolymers, Eudragit RS PO and Eudragit RL PO (95:5), were pre-plasticized by a hot-melt extrasion process using a plasticizer and thermal lubricant, and then cryogenically ground into a fine powder. The powder coating process involved three steps including priming, powder layering and curing. The use of a solid primer at the initial stage of powder coating increased the adhesion of the pre-plasticized acrylic polymers to the substrates. At 8% w/w total weight gain, immediate release theophylline tablets that were powder-coated with Eudragit RS PO/RL PO demonstrated a 12-h sustained release profile. The theophylline release rate of powder-coated tablets was significantly influenced by the curing temperature, plasticizer concentration, coating level and particle size of the coating powder. Eudragit RS PO/RL PO powder-coated tablets demonstrated a stable drug release profile after 3-month storage at 25°C/60% RH and 40°C/75%RH. This novel powder coating process was demonstrated to be an efficient coating method to produce stable sustained release dosage forms.