Bioadhesive formulations have a wide scope of application for both systemic and local effects of the drug. The oral transmucosal drug delivery bypasses liver and avoids pre-systemic elimination. The strategies to overcome such obstacles include the employment of new materials that, possibly, combine mucoadhesive and penetration enhancer properties and the design of novel drug delivery systems which, besides improving patient compliance, favor a more intimate contact of the drug with the absorption mucosa. Cellulose derivatives like HPMC is having good mucoadhesive property however it's potential can be increased by inclusion of plant derived gum like gum karaya. Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) with pain relieving properties. It is used to treat many painful conditions, inflammation, swelling, and /or stiffness caused by several conditions and acute postoperative pain. One form of diclofenac, the potassium salt, is more effective at the same dose than the other form of diclofenac, the sodium salt. In view of first pass effect it has been selected as model drug for the study.

Tailoring or modulation of drug release from delivery systems comprises a major area of research in pharmaceutical field where the primary objective is to either sustain drug release or to design orodispersible tablets. This objective can be successfully achieved by use of a class of natural excipients - gums and mucilages. These polysaccharidic plant-derived biopolymers because of their unique swellability in aqueous medium can exert a retardant effect on drug release or can act as superdisintegrant, depending on the concentration used in the formulation. Mechanism of drug release from hydrophilic matrices consisting of gums and mucilages is based on solvent penetration-induced polymer relaxation, diffusion of entrapped drug followed by degradation or erosion of the matrix. The degree and time-scale of swelling contributes significantly to the kinetics of drug release. Drug diffusion from polysaccharidic hydrogel may be of either Fickian, Case II or anomalous transport type. The book has been designed to highlight on the bifunctional aspect of the natural gums primarily because of their concentration-dependent effect on drug release and their high degree of swellability.