Bilayer Tablet: A Review

Over the past 30 years as the expense and complications involved in marketing new drug entities have increased with concomitant recognition of the therapeutic advantages of controlled drug delivery systems. Bi-layer tablet is new era for the successful development of controlled release formulation and its consists of monolithic partially coated and multilayered matrices. The goal in designing sustained or controlled delivery systems is to reduce the frequency of the dosing or to increase effectiveness of the drug by localization at the site of action, reducing the dose required or providing uniform drug delivery. Bilayer tablet is suitable for sequential release of two drugs in combination, separate two incompatible substances and also for controlled release tablet in which one layer is immediate release as initial dose and second layer is maintenance dose. Bilayer tablet technology has improved to overcome the shortcoming of the single layered tablet. Several pharmaceutical companies are interested to developing bilayer tablets for a variety of reasons : patent extension, increase of therapeutic efficacy and to reduce capital investment. This article explains about different techniques of bilayer tablet and why the development and production of quality bilayer tablets needs to be carried out on purpose-built tablet presses to overcome common bi-layer problems, such as layer-separation, insufficient hardness, inaccurate individual layer weight control, cross-contamination between the layers, lack of proper bonding of two layers, stress due to high suppression force degrades certain active ingredients, chance of increase in impurities,.etc.