bioadhesive system

A bioadhesive system is a dosage form designed to stick to a body tissue and hold its position, like a plaster that grips the skin, so the medicine stays in contact with the surface for far longer than it otherwise would.

Bioadhesion is the broad term for a material sticking to any biological surface; when that surface is a mucous membrane, the more specific word mucoadhesion is used. The sticking is achieved with polymers that first wet and spread on the tissue, then bond to it by interpenetrating its surface and forming hydrogen bonds and other weak attractions. Bioadhesive systems include buccal patches held against the cheek, vaginal and rectal forms, ocular inserts, and gels that gel in place after application.

Prolonged, intimate contact is the whole point: it can increase how much drug is absorbed, allow less frequent dosing, and let a drug be delivered across a chosen surface such as the cheek to bypass first-pass metabolism. The limitations are that the body continually renews mucus and sheds surface cells, so adhesion is temporary, patient comfort and acceptability matter (a patch in the mouth must not be irritating), and the strength and duration of adhesion vary with the tissue and its moisture.