ABSORPTION ENHANCERS IN NASAL DRUG DELIVERY - EFFICACY AND SAFETY

Efficacy and safety of nasal absorption enhancers depend on many different parameters, such as their influence on nasal epithelial membrane barriers, the enzymatic activities in the nasal cavity, and the mucociliary clearance. Large interspecies differences appear to exist in the nasal absorption of drugs. Nasal absorption enhancers, although very effective in some cases, differ substantially in efficacy and safety. For a number of enhancers like surfactants, bile salts and fusidate derivatives a good relationship (similarity in rank order) can be established between the morphological damage and the influence on the ciliary beat frequency (CBF) of nasal epithelial tissue, making CBF measurements a valuable tool in the search for safe nasal absorption enhancers.