Use of acryclic and metacrylic acid derivatives as sustained release matrices for theophylline hydrate tablets

Carbopol 941, an acrylic acid polymer and "Eudragit L100-55, a metacylic acid polymer, were compared as sustained release matrix devices for theophylline hydrate tablets. The theophylline tablets containing 0 to 30% of either of the polymer were prepared using the direct compression method. In vitro drug release studies were carried out in 0.1 N HCl, simulated gastric fluid without pepsin (SGF) and simulated intestinal fluid without pancreatin (SIF). A relatively prolonged release of theophylline from the two polymer matrices for an 8 hr-release period was detected. At 20% w/w and in 0.1 N HCl there were no significant drug releases from the two matrices within the first 2 hrs; after this period, carbopol 941 exerted a more retardant effect on drug releases. At 30% w/w, release rate from Eudragit L100-55 was faster for a 6 hr period with a steady state release maintained at 50% for 4 hrs. The rates of theophylline release from the matrices depended on the pH of the dissolution media and on the properties of the two matrices. While drug release from Carbopol 941 was faster in acidic media, faster release occurred from Eudragit L100-55 in alkaline medium. Drug release kinetics from the two matrices was of a general mixed order, but the first order and the diffusion-controlled mechanism were occurring simultaneously. We can conclude that carbopol 941 can be considered a better-sustained release matrix in directly compressed theophylline tablets comparing with Eudragit L100-55.