Nifedipine controlled delivery by sandwiched osmotic tablet system

The sandwiched osmotic tablet system (SOTS), which is composed of a sandwic hed osmotic tablet core surrounded by a cellulose acetate membrane with two orifices: on both side surfaces, has been successfully prepared with the p urpose of delivering nifedipine. The sandwiched osmotic tablet core consist s of a middle push layer and two attached drug layers. Influences of tablet formulation variables, orifice size and membrane variables on nifedipine r elease of SOTS have been studied. It was found that potassium chloride amou nt of push layer and polyethylene oxide amount of drug layer had markedly p ositive effects on nifedipine release. A push layer/drug layer co-controlle d osmotic delivery mechanism and the optimal core formulation have been pro posed. The appropriate orifice size was observed in the range of 0.50-1.41 mm. It was also found that the drug release rate of SOTS could be increased by incorporating hydrophilic plasticizer in the membrane, whereas it decre ased with hydrophobic plasticizer. It has been observed that the SOTS gives fairly comparable in vitro release features as that of commercialized push -pull osmotic tablet system, such as an approximately constant rate up to 2 4 h and independence of release media and agitation rate. Exempting side id entification before drilling, it is easier to prepare the SOTS than the pus h-pull osmotic tablet system. (C) 2000 Elsevier Science B.V. All rights res erved.