Mucoadhesive polymers as efficient drug delivery systems

The drug action can be reinforced as a result of the development of new drug delivery systems. Over the past few decades, mucosa/ drug delivery has received a great deal of attention to improve both the local and systemic drug effects. Drug delivery across the mucosa bypasses the first-pass hepatic metabolism and avoids the degradation caused by the gastrointestinal enzymes. Mucoadhesive dosage forms are designed to enable prolonged retention at the desirable site of action, provide sustained release of drug and thus, lead to an improved bioavailability, as well as therapeutic outcomes. Compared with other mucosa/ rissues, vaginal mucosa/ cavity is more appropriate and attractive for drug delivery. In addition, a prolonged contact of mucoadhesive dosage forms with the vaginal mucosa may be achieved more easily than at other absorption sites like rectum or intestinal mucosa. This review aims to highlight the recent advances in the study of mucoadhesion and mucoadhesive polymers. It provides an overview of the structure of mucosa/ membranes, the mechanism and theories involved in mucoadhesion, and finally it describes briefly the main characteristics and the advantages of vaginal mucoadhesive drug delivery systems compared with other delivery systems

Chitosan microspheres as potential carriers for colon targeting

Chitosan microspheres have been in the focus of increasing interest as polymeric drug carriers due to their appealing properties such as biocompatibility, biodegradability, low toxicity, mucoadhesion and relative low cost of production. Gel formation can be obtained by interactions of chitosan with low molecular we. counter-ions such as polyphosphates. However, one drawback of using this natural polysaccharide for oral controlled release dosage forms is its fast dissolution rate in the stomach. Since chitosan is positively, charged at low pH values [below its pKa value], it spontaneously associates with polyanions to form polyelectrolyte complexes [PEC]. These PEC these PEC exhibit favorable physicochemical properties with preservation of chitosan's biocompatible. characristics. These complexes are therefore good candidates for the design of colon-targeted dosage forms. Various techniques are used for preparing chitosan microspheres which have been reviewed. This review also includes factors that affect the release characteristics of drugs from chitosan microspheres