Mucoadhesive systems

An alternative to the oral route is the buccal mucoadhesive system. The Striant buccal system adheres to the inside of the mouth and the testosterone is absorbed through the oral mucosa and delivered to the systemic circulation. There is no first-pass effect, as the liver is bypassed by this route of administration. Patients apply a 30-mg tablet to the upper gum twice daily. The cost is similar to that of the patch or gel. Side effects unique to this dosage form include oral irritation, bitter taste, and gum edema. 

The failure in increasing residence time of mucoadhesive systems in the human intestinal tract has led scientists to the evaluation of multifunctional mucoadhesive polymers. Research in the area of mucoadhesive drug delivery systems has shed light on other properties of some of the mucoadhesive polymers. One important class of mucoadhesive polymers, poly(acrylic acid) derivatives, has been identified as potent inhibitors of proteolytic enzymes [72-74]. The interaction between various types of mucoadhesive polymers and epithelial cells has a direct influence on the permeability of mucosal epithelia by means of changing the gating properties of the tight jrmctions. More than being only adhesives, some mucoadhesive polymers can therefore be considered as a novel class of multifunctional macromolecules with a number of desirable properties for their use as delivery adjuvants [72,75]. 

In order to overcome these issues, various noninvasive routes are tested for the delivery of peptides. The oral mucosa due to its high vascularity, avoidance of hepatic first-pass metabolism, and the absence of degradative enzymes normally present in the GI tract has been explored as a suitable route for peptide delivery. Several studies of peptide absorption through the oral mucosa have been conducted, and the results have been impressive in some cases, and not in the others. The development of mucoadhesive systems for buccal and sublingual delivery has increased the absorption and bioavailability of peptides, and various formulations have been developed using these systems. 

The factors that hinder the absorption of peptides through the intestinal epithelium, namely high molecular weight, charge, and hydrophilicity also affect their absorption through the oral mucosa. Combinations of mucoadhesive systems, absorption enhancers, and enzyme inhibitors have enabled better absorption. 

Conventional systems do not offer sufficient flexibility in controlling drug-release rate and sustaining the release over time periods extending from days to months. Therefore specific modified release vaginal delivery systems are continuously under development and are based on mucoadhesive systems. Penetration enhancement may represent a necessary feature for certain delivery systems, particularly when the absorption regards a macromolecule (such as a peptide or a protein). 

Design of Retentive Delivery System Based on Adhesion Mucoadhesive Systems... 

Mucus and salivary clearance reduces the retention time of drags within the oral cavity and thus the opportunity for absorption. This may be overcome by the use of mucoadhesive systems. 

In order to address the rapid removal of pharmaceuticals due to the mucociliary clearance mechanism, mucoadhesive systems that promote bioadhesive interactions with a mucous membrane and increase retention time by prolonging the contact between the formulation and absorption site have been evaluated as a strategy to enhance systemic absorption following... 

Bonferoni, M.C., Chetoni, R, Giunchedi, P., Rossi, S., Ferrari, F., Burgalassi, S. Caramella, C. Carrageenan-gelatin mucoadhesive system for ion-exchange based ophthalmic... 

Mucoadhesion invariably involves the presence of a hydrated gel phase. The hydrogel may be applied as such to the mucosal surface or the hydrated gel phase can be formed in situ upon hydration of a solid mucoadhesive system in contact... 

Deacon, M. R, McGurk, S., Roberts, C. J., et al. Atomic force microscopy of gastric mucin and chitosan mucoadhesive systems. J. Biochem. 2000,348,557-563. 

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