Bi-layer tablet

Gastro retentive drug delivery system (GRDDS), these dosage forms are designed to achieve prolonged gastric residence time in controlled release manner. The floating drug delivery system (FDDS) also comes under the gastro retentive drug delivery system. These type of formulations helps to improve the solubility of poorly soluble drugs and enhances the bioavailability of the drug. In gastrointestinal tract the absorption of dosage form or drug molecule is a highly variable process. To overcome all these physiological problems Novel Drug Delivery System (NDDS) plays an important role. FDDS works on the principle of buoyancy (the tendency of an object or a molecule float in a fluid or the upward force that a fluid exerts on an object) which allows the drug to remain in the gastric environment for a prolonged period of time without rapid passing into the intestine. Floatation of a drug is due to bulk density less than gastric fluids and so, remain buoyant in the stomach for a prolonged period of time. Releasing the drug slowly at the desired rate and increase the bioavailability of narrow absorption window drugs. This review helps to know the floating drug delivery system principle, advantages and disadvantages, need for floating bilayer tablets, challenges in bi-layer tablet manufacturing and characterization and evaluation methods for bilayer floating tablets.

Bilayer tablet is the novel technology for the development of controlled release formulation. Developing a combination of two or more active pharmaceutical ingredients in a single dosage form is known as a bilayer tablet. Bilayer tablet is more suitable for gradual release of two active ingredients in combination. The preparations of bilayer tablet were needs due to separate incompatible active pharmaceutical ingredient (APIs) for each other. Bilayer tablets material involves both the compressibility and consolidation. The primary objective of sustained release drug delivery is to ensure safety and to improve efficacy of drugs as well as patient compliance. 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 as initial dose and second layer is maintenance dose. Bilayer tablet is improved beneficial technology to overcome the shortcoming of the single layered tablet. In the case of bi-layered tablets drug release can be rendered almost unidirectional if the drug can be incorporated in the upper non-adhesive layer its delivery occurs into the whole oral cavity. Keywords: Active Pharmaceutical Ingredient, Bi-layer tablet