PERMEABILITY AND THE PATHOPHYSIOLOGY OF ORAL-MUCOSA

Drug delivery across the oral mucosa demands that compounds at the sur face of the tissue must first penetrate the superficial epithelial per meability barrier before they can exert a local or systemic effect. In the latter case, it is also necessary for there to be adequate vascul ar perfusion of the underlying connective tissue. Normal processes suc h as aging appear to have minimal effect on permeability, but developm ental and reactive changes, ranging from pathological thickening (hype rplasia and hyperkeratosis) to inflammation and thinning or atrophy ar e likely to be associated with increased permeability. Similarly, dise ase entities such as aphthous ulceration or blistering diseases (vesic ulo-bullous lesions) are likely to lead to the tissue being more perme able because of the damage to the barrier layer. Furthermore, delivery devices involving topical adhesives and occlusion will be more diffic ult to utilize if the mucosal surface is compromised. On the other han d, the oral cavity is readily accessible, free from extremes of pH or proteolytic enzyme activity and the mucosa heals rapidly and is less r eactive to drugs than is the skin.