Nasal drug delivery systemic absorption

Microspheres can be used as nasal drug delivery systems for systemic absorption of peptides and proteins. 

Although this section deals mainly with the advantages of excised tissues with respect to nasal drug delivery studies, it is important to highlight some important attributes of nasal in situ perfusion model. Although this method does not provide data on systemic absorption, it enables study of the interactions of nasal mucosal enzymes, peptide substrates, and metabolic inhibitors and their implications for nasal drug absorption [13], It also enables the rate of nasal drug absorption to be determined. 

Both the type of drug delivery system and the specific type of delivery device can affect drug absorption via the nasal route. The choice of delivery system depends mainly on the physiochemical properties of the drug, its desired site of action, and, more importantly, patient compliance and marketing aspects. The formulations most commonly used in nasal delivery are solutions, suspensions, gels, dry powders, and, most recently, nanoparticulate formulations. 

Alternative means that help overcome these nasal barriers are currently in development. Absorption enhancers such as phospholipids and surfactants are constantly used, but care must be taken in relation to their concentration. Drug delivery systems, including liposomes, cyclodextrins, and micro- and nanoparticles are being investigated to increase the bioavailability of drugs delivered intranasally [2]. 

As an exemplification, a novel system called PecSys (PS), which is a pectin based drug delivery system, is developed to gel on mucosal surfaces when applied. These systems are currently focused in their application in intranasal delivery of drugs where it plays the role of optimizing the absorption of lipophilic drugs into the circulation. The PS based systems were commonly used for the intranasal formulations constituting opioid analgesics for the rapid pain relief The lead product that uses the PS system is NasalFent, which is a fentanyl nasal spray formulation [82]. 

J. Wang, Y. Tabata, and K. Morimoto. Aminated gelatin microspheres as a nasal delivery system for peptide drugs Evaluation of in vitro release and in vivo insulin absorption in rats. J Control Release 113 31-37 (2006). 

The nasal route of drug delivery is used for the direct administration of medicines to the nose for treatment of local conditions or the systemic delivery of compounds that are not easily delivered by the oral route. It is also suggested that there may be a direct route for drug absorption to the central nervous system (CNS) from the olfactory region of the nose. 

The nasal application of drugs is an area of growing interest (21) and a number of publications has shown that simple molecules as well as more complex species (eg calcitonin, insulin etc) can be well absorbed by this route, either directly or in the presence of so-called absorption enhancers. One problem with such materials could be too rapid clearance of the delivery system from the nasal cavity through the efficient action of the mucociliary system. For this reason Ilium has considered the use of microsphere systems. 

---