Sandwiched osmotic tablet core for nifedipine controlled delivery

The sandwiched osmotic tablet core, which is composed of a middle push layer and two attached drug layers, has been prepared and systematically studied with the purpose of delivering water-insoluble nifedipine. The advantage of the sandwiched osmotic tablet system over the commercialized push-pull osmotic tablet system is its simplicity of preparation, as the surface identification was avoided. It was observed that polyethylene oxides (PEO) with molecular weight (MW) of 300,000 and 8,000,000 g/mole were suitable for the thickening agent of drug layer and the expandable hydrogel of push layer, respectively. The weight ratio of 190/190 for drug layer/push layer was also found to be suitable. It has been observed that PEO amount of the push layer and the KCl amount of the drug layer had profoundly positive influence on nifedipine release. A push layer/drug layer co-controlled osmotic delivery mechanism has been proposed and the optimal tablet formulation has been obtained. It was also found that PEO and nifedipine were miscible, which may support the application of PEO in nifedipine dosage forms. Meanwhile, the PEO/nifedipine binary phase diagram has been constructed. The sandwiched osmotic tablet system can deliver nifedipine in an approximate zero-order rate up to 24 hours. It may be potentially used for the delivery of water-insoluble drugs.