Particle size nasal deposition

There are only scant data on nasal deposition. The available studies reported utilized micron sized particles and the dominant mode of deposition is impaction. This is not the case for the particles considered here and diffusion and turbulent diffusion are the mechanisms of interest. George and... 

Breslin (1969) measured nasal deposition for both the attached and unattached fraction of radon daughters in a laboratory atmosphere and found it to be about 1% for the attached and 60% for the unattached fraction. The size characteristics of the unattached fraction is assumed to be that found by Knutson et al. (1983) for older air of 0.005 pm (D=0.0025 cm2/sec). No data are available for nasal deposition of the small sized kerosene heater particles, 0.030 pm, and the value for the attached radon daughters of 1.3% is used. 

Harris, A.S., et al. 1988. Effect of viscosity on particle size, deposition and clearance of nasal delivery systems containing desmopressin. J Pharm Sci 77 405. 

Increasing the viscosity of solutions administered to the nasal cavity with, for example, methylcellulose, hyaluronan etc., has been shown to increase the time the formulation is retained in the nasal cavity and to enhance the absorption of certain drugs. It is thought that, up to an optimum viscosity, higher viscosity solutions give a more localized deposition in the anterior portion of the nose (i.e. low clearance site). As viscosity can affect droplet size by altering the surface tension of the solution, the more localized deposition in the anterior of the nose may be due to viscosity-related changes in the particle size of the delivered droplets. 

Microspheres intended for nasal administration need to be well characterized in terms of particle size distribution, since intranasal deposition of powder delivery systems is mostly determined by their aerodynamic properties and particle sizes. Commonly used methods for particle size determinations described in the literature are sieving methods [108], light microscopy [58], photon correlation spectroscopy [66], and laser diffractometry [25,41,53,93], The morphology of the microparticles (shape and surface) has been evaluated by optical, scanning, and transmission electron microscopy [66, 95],... 

The particle size of nasal powders is not regarded as critical as for inhalation powders. For inhalation, the particle size should be in the range of 1-5 pm. To allow deposition in the nasal cavity, this fine particular fraction... 

Recently, a comparison study of deposition pattern of aqueous nasal spray pumps and non-portable nebulizers was published. The obtained controversial results showed a relative standard deviation of 35-80%. This demonstrates the variations in nasal anatomy and physiology from individual to individual. Other stud-ies indicate that differences in the spray performance, i.e., spray angle and particle size distribution, of delivery systems do not necessarily result in different in vivo deposition. 

While the removal of airborne contaminants by the nose is effective, this action also renders this organ susceptible to toxic damage. The behavior of the inhaled substances in the NP airways and the ultimate determination of whether they are deposited or exhaled depends on numerous factors for example, breathing patterns that influence nasal airflow rates and the chemical and physical properties of the airborne material, such as size, shape, water solubility, and reactivity. Soluble particles may, once deposited, rapidly enter the blood circulation and be transported systemically. Thus, the effective dose of toxicant delivered to the target tissue depends on factors other than the environmental concentration. 

The dominant route of human exposure to wood dusts is inhalation. In fact, most significant health effects seem to result from direct contact of the inhaled wood dusts with tissues of the respiratory tract. Because of the wide distribution of wood dust particle sizes, there is potential for deposition throughout the respiratory system. However, the majority deposit in the upper airways, primarily in the nose. This correlates well with observations that the most important health effects, such as upper respiratory symptoms and sino-nasal cancer, occur in the upper airways. While ingestion also is common, no adverse health effects were reported. Dermal contact also occurs routinely, occasionally causing dermatitis. 

Various studies (Bond et al. 1984 Newman et al. 1987a) have found droplet size distributions of aqueous nasal spray products to have mass mean (median) diameter values between 44 and 62 pun. These studies showed that the majority of the dose was deposited locally in the anterior one-third of the nose. The relationship between retention time and viscosity has shown that the addition of various concentrations of methylcellulose (MC) to a metered spray pump containing desmopressin resulted in a dose-related increase in mean particle size from 51 pan (0 percent MC) to 81 pan (0.25 percent MC) to 200 pirn (0.5 percent MC), without a change in mean spray weight. The longest retention time was observed for the 0.25 percent MC solution, which was attributed to its particle size (81 p,m) and not to an increase in viscosity, since a decrease in retention time was observed for the highest viscosity (0.5 percent MC) solution... 

To study particle transport and deposition in the nasal passage, 7(X)-1,2(X) particles of different sizes were introduced at the nostril with a uniform distribution, and their corresponding trajectories were analyzed. Figure 50 shows sample stream traces. It is seen that the stream traces are focused in certain areas of the nasal passage. 

Deposition of particles of the thermodynamic size range has not been studied extensively in humans. Cheng and co-workers (185) measured deposition efficiencies for 4-, 8-, 20-, and 150-nm particles in ten healthy adult, male volunteers. For nose-in mouth-out breathing at flow rates of 333 cm s, deposition fractions for these particle sizes were 36.7 10.6 (mean SD), 21.2 8.9, 11.1 7.7, and 5.2 3.8%. However, because expiratory deposition in the mouth is not negligible for particles in the thermodynamic domain, these values overestimate nasal deposition. The large SD values indicate that intersubject deposition variability is notable in the thermodynamic domain. Mean nasal deposition, as de-... 

In general, particles or droplets in the size range 5-10 wm tend to deposit in the nasal passages. Although the extent and site of particle deposition can be estimated from a knowledge of the aerodynamic size distribution of the aerosol, the situation can be complicated by the fact that the size of the particle can increase (and possibly its density decrease) as a result of water condensation, due to the humidity change upon entering the nasal cavity. 

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