Mucoadhesive retentive system

The size of the delivery system varies with the type of formulation, i.e., a buccal tablet may be approximately 5-8 mm in diameter, whereas a flexible buccal patch may be as large as 10-15 cm in area. Mucoadhesive buccal patches with a surface area of 1-3 cm are most acceptable. It has been estimated that the total amount of drug that can be delivered across the buccal mucosa from a 2-cm system in 1 day is approximately 10-20 mg.f The shape of the delivery system may also vary, although for buccal drug administration, an ellipsoid shape appears to be most acceptable. The thickness of the delivery device is usually restricted to only a few millimeters. The location of the delivery device also needs to be considered. A mucoadhesive retentive system is preferred over a conventional dosage form. A bioadhesive buccal patch would appear to be the most appropriate delivery system because of its flexibility and the area of the buccal mucosa available for its application. The maximal duration of buccal drug retention and absorption is approximately 4-6 h because food and/or liquid intake may require removal of the delivery device. 

Stimulation of saliva production is under sympathetic and parasympathetic control. Parasympathetic stimulation produces a serous watery secretion, whereas sympathetic stimulation produces much thicker saliva. Drug delivery systems, therefore, should not be placed over a duct or adjacent to a salivary duct, as this may dislodge the retentive system or may result in excessive wash-out of the drug or rapid dissolution/erosion of the delivery system making it difficult to achieve high local drug concentrations. If a retentive system is placed over salivary ducts, the reduced salivary flow rate may produce less or no mucus which is required for the proper attachment of a mucoadhesive delivery device. 

Bioadhesive formulations and microsphere delivery systems in particular have attracted much attention. As drug formulations are usually rapidly removed from the site of deposition by the mucociliary clearance, increasing the retention time of drug in the nasal cavity via bioadhesion can increase bioavailability [28], Bioadhesion may be defined as the ability of a material (synthetic or biological) to adhere to a biological tissue for an extended period of time. When applied to a mucous membrane, a bioadhesive polymer may adhere primarily to the mucus layer or epithelial cell surface in a phenomenon known as mucoadhesion [29,30]. The bioadhesive properties of a wide range of materials have been evaluated over the last decade. 

Both for local and systemic therapy to prevent poor retention, messiness, and leakage associated with conventional vaginal dosage forms, it is useful and sometimes necessary to prolong and improve the contact between the drug and the mucosa. The presence of mucoadhesive agents in the formulation could enable the attainment of such a goal. 

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... 

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