polymers.

Since, the last four decades, the concept of mucoadhesion has achieved a much valuable interest in the various fields of pharmaceutics. There are many advantages of mucoadhesive buccal drug delivery system that made this a novel drug delivery system for the local as well as systemic delivery of various drugs. The main advantage of this drug delivery system is that it prolongs the residence time of the dosage form at the site of application. Due to the high blood supply and relatively high permeability of the buccal mucosa, the buccal cavity is the best option for both local as well as systemic delivery of various drugs. The main prospect of writing this review article is to present comprehensive information related to mucoadhesion and mucoadhesive drug delivery systems. The article has highlighted all the aspects of mucoadhesive drug delivery systems which will be helpful for researches and academics. The article includes detailed information about mucosa- the anatomy and physiology, the mechanisms and theories related to mucoadhesion, evaluation parameters of mucoadhesive dosage forms, mucoadhesive polymers and novel approaches related to mucoadhesive drug delivery system. Drug actions can be improved by new drug delivery system, such as mucoadhesive system. This system remains in close contact with the absorption tissue, the mucous membrane, releasing the drug at the action site leading to improvement in both local and systemic effects. The potential merits and demerits of mucoadhesive drug delivery as well as that of the polymers are also discussed. It helps enhance the bioavailability through bypassing the first-pass metabolism effect. The mucosal surface better absorption and prolong resident time. Bioadhesion can be defined as the phenomenon of interfacial molecular attractive force in midst of the surface of the biological substrate and the natural or synthetic polymers, which allows the polymers to adhere to the biological surface for an extended period of time.

Mucoadhesive dosage forms may be designed to enable prolonged retention at the site of application, providing a controlled rate of drug release for better therapeutic results. Mucoadhesive drug delivery systems are used to prolong the residence time of the dosage form at the site of application or absorption and to facilitate intimate contact of the dosage form with the underlying absorption surface to improve and enhance the bioavailability of drug. Some of the promising plymers that have been commonly used in these systems include polycarbophil, carbopol, lectins, chitosan, carboxymethylcellulose, pectin, carragenan, alginic acid, polylysine, polybrene, polyethylene glycol, polyvinyl pyrrolidone , dextran etc. Now  scientists are developing mucoadhesive micro and nanoparticulate systems by using  novel mucoadhesive polymers for better therapeutic results and site specific targeting with lesser side effects. Improvements in mucoadhesive based oral delivery and, in particular, the development of novel, highly-effective and mucosa-compatible polymers, are creating new commercial and clinical opportunities for delivery of narrow absorption window drugs at the target site to maximize their efficacy. This review is an effort to provide information on such mucoadhesive drug delivery systems that are developed for oral, buccal, nasal, rectal and vaginal routes for both systemic and local effect.