D.D. Chechare

Bilayer tablets are planned by way of one layer of drug for immediate release with the second layer designed to release drug later, either as a second dose or in an sustained release form. The bilayer tablets with two incompatible drugs can also be prepared by compressing separate layers of each drug so as to minimize area of contact between two layers of two API. To manufacture sufficient tablet formulation, definite necessities such as sufficient mechanical strength and desired drug release profile must be meet. At times, this may be difficult task for formulator to achieve these conditions especially in bilayer tablet formulation where double compression technique is involved, because of poor flow and compatibility characteristic of the drug which will result in capping and/or lamination. The compaction of a material involves both the compressibility and consolidation.

Mucoadhesive drug delivery systems interact with the mucus layer covering the mucosal epithelial surface, and mucin molecules and increase the residence time of the dosage form at the site of absorption. The drugs which have local action or those which have maximum absorption in gastrointestinal tract (GIT) require increased duration of stay in GIT. Thus, mucoadhesive dosage forms are advantageous in increasing the drug plasma concentrations and also therapeutic activity. In this regard, this review covers the areas of mechanisms, polymers used in mucoadhesion, factors influencing the mucoadhesive and also various mucoadhesive dosage forms. Keywords: Mucoadhesion, theories, mucoadhesive dosage forms.