Recent Apporaches in Bilayered Technology: Review

Bilayered tablet is an important pharmaceutical technology for the successful development of controlled release formulation along with various features to provide a way of successful drug delivery system. Bi-layer tablet is suitable for sequential release of two drugs in combination, to separate incompatible substances and also formulating sustained release tablet in which one layer is immediate release as initial dose and second layer is maintenance dose. Now days the pharmaceutical companies are currently developing bi-layer tablets due to variety of reasons such as patent extension, therapeutic benefit and a marketing strategy. To reduce capital investment, quite often existing but modified tablet presses are used to develop and produce such tablets. This article explains about different techniques of bilayered tablet preparation the development and production of bilayered tablets needs to be carried out on purpose built tablet presses to overcome common bilayered problems such as layer separation, insufficient hardness, and inaccurate individual layer weight control, cross-contamination between the layers, reduced yield and evaluation of bilayered tablets. INTRODUCTION: Bilayer tablets have some key advantages compared to conventional monolayer tablets. For instance, such tablets are commonly used to avoid chemical incompatibilities of formulation components by physical separation. In addition, bilayer tablets have enabled the development of controlled delivery of active pharmaceutical ingredients with predetermined release profiles by combining layers with various release patterns, or by combining slowrelease with immediate-release layers. Bi-layer tablet is suitable for sequential release of two drugs in combination, separate two incompatible substances and also for sustained release tablet in which one layer is immediate release layer delivers initial dose and second layer delivers maintenance dose 1, . The bilayer tablet is a concept utilized by Skye Pharma PLC in their Geomatrix tablet, which is composed of different layers. The system allows the incorporation of more than one drug into the dosage form. Formulation of layers from different polymers allows manipulation over more than one rate-controlling polymer, thus enabling different types of drug delivery of one or more drugs, i.e. where the drug may be released with a bolus and then at a controlled rate or by targeted drug delivery in the GI tract using pH dependant polymers.