Mucoadhesion; A prerequisite or a constraint in nasal drug delivery?

Nasal drug administration has frequently been proposed as the most feasible alternative to parenteral injections. This is due to the high permeability of the nasal epithelium, allowing a higher molecular mass cut-off at approximately 1000 Da and the rapid drug absorption rate with plasma drug profiles sometimes almost identical to those from intravenous injections. Nasal drug administration is presently used for local therapies within the nasal cavity. Anti-allergic drugs and nasal decongestants are the most common examples. However, nasal drug administration for systemic effects has been practiced since ancient times. Nasallyadministered psychotropic drugs by native Indians, the use of tobacco snuffs, and nasal administration of illicit drugs such as cocaine are all well known.