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\ub0C/60% RH and 40\ub0C/75%RH. This novel powder coating process was demonstrated to be an efficient coating method to produce stable sustained release dosage forms

A novel powder coating process for attaining taste masking and moisture protective films applied to tablets

A novel powder coating process was developed for the application of taste masking and moisture protective films on tablets while avoiding the use of solvents or water. The coalescence of particles to form a polymeric film was investigated through studies of dry powder layering of micronized acrylic polymer (E PO) to produce free films. Theophylline containing tablets were coated with the same acrylic polymer in a laboratory scale spheronizer using a powder coating technique. The dry powder layer delayed the onset of drug release in pH 6.8 medium, depending on the coating level, while no delay was observed in pH 1.0 medium. The presence of hydrophilic polymers in the acrylic coating layer decreased the lag time for drug release in pH 6.8 medium, while only the presence of HPMC in the film slowed the drug release rate in acidic medium. The dry coating process was demonstrated to be a reliable alternative to solvent or aqueous film coating technologies for applying taste masking and moisture protective film coats onto compressed tablets. A controlled drug release profile was achieved in pH 6.8 media

Physicochemical characterization and mechanisms of release of theophylline from melt-extruded dosage forms based on a methacrylic acid copolymer

The purpose of the current study was to investigate the physicochemical properties of melt-extruded dosage forms based on Acryl-EZE(R) and to determine the influence of gelling agents on the mechanisms and kinetics of drug release from thermally processed matrices. Acryl-EZE(R) is a pre-mixed excipient blend based on a methacrylic acid copolymer that is optimized for film-coating applications. Powder blends containing theophylline, Acryl-EZE(R), triethyl citrate and an optional gelling agent, Methocel(R) K4M Premium (hydroxypropyl methylcellulose, HPMC, hypromellose 2208) or Carbopol(R) 974P (carbomer), were thermally processed using a Randcastle single-screw extruder. The physical and chemical stability of materials during processing was determined using thermal gravimetric analysis and HPLC. The mechanism of drug release was determined using the Korsmeyer-Peppas model and the hydration and erosion of tablets during the dissolution studies were investigated. The excipient blends were physically and chemically stable during processing, and the resulting dosage forms exhibited pH-dependent dissolution properties. Extrusion of blends containing HPMC or carbomer changed the mechanism and kinetics of drug release from the thermally processed dosage forms. At concentrations of 5% or below, carbomer was more effective than HPMC at extending the duration of theophylline release from matrix tablets. Furthermore, carbomer containing tablets were stable upon storage for 3 months at 40 degrees C/75% RH. Thus, hot-melt extrusion was an effective process for the preparation of controlled release matrix systems based on Acryl-EZE(R). (C) 2005 Elsevier B.V. All rights reserved