Inhalant properties aerosols

Even when the appropriate inhaler is chosen, the influence of the disease state cannot be ignored. Disease states can influence the dimension and properties of the airways and hence the disposition of any inhaled drug. Thus, great care must be taken when extrapolating the findings based on intratracheal administration to different animal species in order to predict deposition profiles after inhalation of aerosol formulations by patients suffering from airway disease. DPIs are not appropriate in many diseases when the ability to have sufficient airflow is hindered. Since many diseases that we would like to treat via pulmonary administration of biomolecules cause a decrease in airflow, we must be careful in the decision of which type of inhalation mechanism to choose. 

The hazard from inhaled uranium aerosols, or any noxious agent, is determined by the likelihood that the agent will reach the site of its toxic action. Two main factors that influence the degree of hazard from toxic airborne particles are the site of deposition in the respiratory tract of the particles and the fate of the particles within the lungs. The deposition site within the lungs depends mainly on the particle size of the inhaled aerosol, while the subsequent fate of the particle depends mainly on the physical and chemical properties of the inhaled particles and the physiological status of the lungs. 

Powder can be easily extracted from its packaging On delivery, coughing and other unpleasant sensations may be induced because the carrier particles deposit in the mouth and throat Little mouth and throat deposition patient does not feel he/she is inhaling an aerosol Formulation process becomes a key factor in the development of the product the properties of the compound to be delivered dominate the performance of the resulting powder... 

Isoetharine, a sympathomimetic agent with bronchodilating properties (aerosol inhaler 340 mcg/metered spray), is indicated in the treatment of bronchial asthma and reversible bronchospasm that may occur with bronchitis and emphysema (see also Figure 94). 

The two main determinants for medicine deposition in the respiratory tract are the aerodynamic size distribution of the aerosol and the manoeuvre with which the aerosol is inhaled. They govern the mechanisms that are respraisible for particle deposition in the lungs. By varying the inhalation manoeuvre, not only the distribution in the airways for the same aerosol is changed in many cases also the amount and properties of the delivered fine particle dose are affected. The complex interplay between inhalation manoeuvre, aerosol properties and site of deposition has led to many misconceptions regarding the best inhaler choice for individual patients and the way these inhalers need to be operated to achieve optimal therapy for the patient. In this chapter the medicine deposition mechanisms for inhaled aerosols are explained as functions of the variables involved. In addition, the working principles of different inhaler types are described and it is discussed how their performance depends on many inhalation variables. Finally, some persistent misconceptions in the literature about the most preferable dry powder inhaler properties and performance are umaveUed. 

In the United States, use of CEC propeUants, designated as PropeUants 11, 12, and 114, is strictly limited to specialized medicinal aerosol products such as metered-dose inhalers. The physical properties and chemical names of these propeUents are given in Table 2. 

Propagated outbreaks of infection relate to the direct transmission of an infective agent from a diseased individual to a healthy, susceptible one. Mechanisms of such transmission were described in Chapter 4 and include inhalation of infective aerosols (measles, mumps, diphtheria), direct physical contact (syphilis, herpes virus) and, where sanitation standards are poor, through the introduction of infected faecal material into drinking water (cholera, typhoid). The ease oftransmission, and hence the rate of onset of an epidemic (Fig. 16.3) relates not only to the susceptibility status, and general state of health of the individuals but also to the virulence properties of the organism, the route oftransmission, the duration of the infective period associated with the disease. 

Battelle Pacific Northwest Labs. 1975. Effect of physico-chemical properties on metabolism of transuranium oxide aerosols inhaled by beagle dogs. Richland, WA Battelle Pacific Northwest Labs. BNWLSA5430. 

Dry powders must be able to flow readily in order to leave the capsule or powder reservoir, but must also generate a fine aerosol enabling the patient to inhale a proper dose. These two requirements are often difficult to achieve simultaneously. Fine powders tend to be eohesive and have poor flow properties. Blending with a carrier phase, pelletization, and other approaches have been used to overcome these limitations. The featmes of blends and homogeneous powders are compared in Table 4 from a DPI device perspective ... 

Adhesive mixtures require large carrier crystals to improve the handhng properties of the powders. Dispersion of the small drng particles over the larger carrier material should assure dose uniformity. However, the small dmg particles shonld be removed from the carrier material dnring inhalation, to render an aerosol clond of respirable particles. If the particles remain on the carrier, month or throat deposition of the drng will occur, which might decrease therapeutic efficacy or cause serious side-effects. 

The potential for liquid aerosols or finely divided powders to be inhaled will be determined by their particle size. Deposition patterns for dusts will depend not only on the particle size of the dust but also the hygroscopicity, electrostatic properties and shape of the particles, and the respiratory dynamics of the individual. Thus, it is only possible to make very general statements about sites of... 

Fujitani, Y., Kobayashi, T., Arashidani, K., Kunugita, N. and Suemura, K. (2008) Measurement of the physical properties of aerosols in a fullerene factory for inhalation exposure assessment /. Occup. Environ. Hyg., 5 (6), 380-389. 

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