Deposition of intranasal glucocorticoids--preliminary study

Intranasal glucocorticoids are the treatment of choice in the therapy of rhinitis. The differences in efficiency of particular medications proven by therapeutic index may result from differences in composition of particular formulations as well as from diverse deposition in nasal cavities. Intranasal formulations of glucocorticoids differ in volume of a single dose in addition to variety in density, viscosity and dispenser nozzle structure. The aim of this report was to analyze the deposition of most often used intranasal glucocorticoids in the nasal cavity and assessment of the usefulness of a nose model from a 3D printer reflecting anatomical features of a concrete patient.

Three newest and most often used in Poland intranasal glucocorticoids were chosen to analysis; mometasone furoate (MF), fluticasone propionate (FP) and fluticasone furoate (FF). Droplet size distribution obtained from the tested formulations was determined by use of a laser aerosol spectrometer Spraytec (Malvern Instruments, UK). The model of the nasal cavity was obtained using a 3D printer. The printout was based upon a tridimensional reconstruction of nasal cavity created on the basis of digital processing of computed tomography of paranasal sinuses. The deposition of examined medications was established by a method of visualization combined with image analysis using commercial substance which colored itself intensively under the influence of water being the dominant ingredient of all tested preparations. On the basis of obtained results regions of dominating deposition of droplets of intranasal medication on the wall and septum of the nasal cavity were compared.

Droplet size of aerosol of tested intranasal medications typically lies within the range of 25-150 µm. All tested medications deposited mainly on the anterior part of inferior turbinate. FP preparation deposited also on the anterior part of the middle nasal turbinate, marginally embracing a fragment of the central part of this turbinate as well together with deposition in the middle and superior nasal meatus reaching the region of nasal ceiling and olfactory field. MF preparation deposited on the anterior part of the inferior turbinate and central part of this turbinate alike. The area of mucous membrane of lateral wall of nasal cavity on which MF deposited was similar to the area achieved after the application of FP preparation but much greater than in the case of FF preparation. FF drug deposition concentrates only on the anterior part of the inferior turbinate. Despite directing the drug to the lateral wall of the nasal cavity a great proportion of examined preparations deposit also on the nasal septum.

The practical application of tridimensional representation (3D printout) of actual geometry of nasal cavity to establish the deposition of inGKS was proven. Droplet size and the geometry of the aerosol cloud introduced into the nostril determine the significant deposition of medication droplets in the anterior part of the nasal cavity. Both physical properties of the drug as well as spraying system applied influence spatial distribution of the drug. The interaction of the air flow with the layer of deposited fluid plays a major role in the deposition of the drug in the nasal cavity, therefore it is so important that the drug does not drain by gravity but remains at the site of deposition which may be reinforced by thixotropic properties of the preparation.