Controlled release theophylline granules coated with poly (ethylacrylate methylmethacrylate) aqueous dispersion by fluidized bed technique

Abstract

Theophylline granules of 18/20 mesh size were coated with different level and lot of Eudragit NE 30D [poly(ethylacrylate methylmethacrylate) aqueous dispersion] containing Cab-O-Sil as an antiadherent by fluidized bed technique. Different ratios of Eudragit NE 30D to hydroxypropylmethylcellulose, a nonelectrolyte, water soluble polymer, or to Eudragit RL 30D (ammonio methacrylate copolymer, type A), a cationic water insoluble but higher permeable polymer, were also employed. The physical properties and the drug release characteristics of coated granules were evaluated. The influences of processing variable, spraying method and atomizing air pressure, were also studied. All Eudragit NE 30D coated granules exhibited smoother surface than uncoated granules. Increasing the level of coating increased the thickness of film, thus the rate of drug release was decreased. Eudragit NE 30D lot B produced rougher and more porous surface coating film than lot A Which led to higher release rate, probably due to the polymer stability. The mode of spray apparently affected the surface characteristics and the flow rates of coated granules but both top spray and bottom spray method caused similar drug release characteristic. This result might be due to differences in the particle motion during the coating process. Higher atomizing air pressure gave less continuous characteristic of film coating probably due to the decreasing temperature in coating chamber which might not be conductive to optimum film formation. Thus, higher drug dissolution was obtained. Addition of hydroxypropylmethylcellulose caused less porous and smoother surface whereas Eudragit RL 30D caused more porous and sponge-like surface. Both polymers dramatically increased the drug dissolution. The release of drug from granules coated with 4.66% Eudragit NE 30D lot A and 13.51% Eudragit NE 30D lot B could conform to the monograph of extended-release theophylline capsules in USP XXIII.