Effects of excipients in nasal powder formulations for systemic drug delivery

The nose as a site of drug delivery offers therapeutic opportunities for a variety of indications, due to the presence of immunocompetent cells, direct contact with the central nervous system and easy access to a permeable and highly vascularised mucosa. However, nasal drug delivery is primarily associated with locally acting drugs, being applied as simple liquid sprays or drops. A new generation of nasal products that takes advantage of the opportunities offered, however, will likely require more sophisticated formulations, as it will need to address specific challenges of the nose, such as the short residence time of inhaled particles. The formulation of nasal powders and the targeted use of excipients are conceivable strategies in this regard. This work investigates influences of excipients in powder formulations that affect systemic absorption of nasally administered druds.

The first part of the work characterises selected mucoadhesive excipients and fillers regarding their potential to extend the nasal residence time with methods that are suitable as screening tools in product development. Furthermore, the excipients were characterised regarding the occurrence of sensory and toxic effects on the nasal mucosa.

Since the benefit of excipient properties depends on the drug to be formulated, in the second part of the work the effect of selected mucoadhesives and fillers was investigated in model formulations. The influences of the formulations on the rheological properties of the nasal fluid, and thus the nasal residence time, on the dissolution and release of the drug, as well as on the permeation of the drug through the epithelium were assessed separately, in order to detect additive and counteracting effects on drug absorption. The consideration of the characterised processes in product development can avoid failures and enable the development of successful nasal products.

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