Bi-layered tablet provide one of the important design approaches to achieve controlled delivery of different drugs with pre-defined release profiles where incompatible drugs, drugs with different indication, and same drug with different release rate can be incorporated in a single unit. Bilayered tablet can be a primary option to avoid physical and chemical incompatibilities between APIs by physical separation, and to enable the development of different drug release profiles like immediate release with extended release property. Generally the pharmacokinetic profile of active drug molecule relies on the fact that the fast release layer provide the loading dose of drug and the sustained release of drug maintain the drug concentration within therapeutic window for longer period of time. Several pharmaceutical companies are currently developing bilayered tablets for a variety of reasons like good therapeutic indication, patient compliances and conventional dosage as compare to other dosage forms. Despite their advantages, due to the use of different materials and complex geometric boundaries between the adjacent layers, the mechanical structures of this drug delivery system have become quite intricate, requiring complicated tablet architectures. This article explains why the development and production of quality bilayer tablet needs to be carried out, the advantages, disadvantages and different methods of formulation as well as study of tablet presses to overcome common bi-layer problems, such as cross-contamination between the layers, layer-separation, individual layer weight control, insufficient hardness etc. for bilayer tablets.
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