Bilayer Tablets-A Review

Bi-layer tablet is a new era for successful development of controlled release formulation along with various features to provide successful drug delivery. Bilayer tablet technology helps in separating the two incompatible substances in which one layer is immediate release as loading dose and second layer is controlled/sustained release as maintenance dose. A Delayed Release dosage form is designed to release the drug at a time other than promptly after administration.The primary aim of using delayed release products is to protect the drug from gastric fluids, to reduce gastric distress caused by drugs particularly irritating to the stomach or to facilitate gastrointestinal transit for drugs that are better absorbed from intestine. Delayed Release products are typically enteric-coated or targeted to the colon. It is fabricated by coating the drug only in the region with a selected pH range It is fabricated by coating the drug-containing core with a PH sensitive polymer combination. It is fabricated by coating the drug only in the region with a selected pH range, Further best formulation is subjected to dissolution studies first in 0.1N HCL buffer for 2hrs followed by phosphate buffer for 4 hrs.