Size Distribution

To avoid oropharyngeal deposition, the drug-carrying particles should be either generated with low Dae (1-3 mm) or, if bigger particles are present, removed before entry into the patient's mouth. The extent to which the loss in the oropharynx is significant will depend on the acceptable variability of lung delivery and the cost of the drug. Since micron-size particles have poor flow properties, traditionally it has been necessary to include some large particles in the formulation. This could be achieved by mixing the micronized drug powder with a carrier material, such as lactose, which consists of particles so large that they will deposit almost entirely in the mouth. A different solution was found to improve the powder flow of cromolyn sodium without an excipient. Respirable-size particles of the drug were made to aggregate into larger, free-flowing spheres (pellets) that are broken up into the primary particles during the generation of the aerosol cloud in the Spinhaler [15].

Calculations predict that substantial changes in regional deposition would result not only if the median diameter of the size distribution is changed but also if the aerosols have different widths of size distribution [50,57-61]. It would be expected that, at the macroscopic level, a more selective delivery would be obtained with less polydisperse aerosols.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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