Relationship Between Pulmonary Deposition and Clinical Effect

Relationship Between Pulmonary Deposition and Clinical Effect 

In order to inhale an aerosolized drug, the patient should activate the inhaler, from which a dose is subsequently emitted (Table 1.). Some of this metered dose is retained in the inhaler, adapter, spacer, or mouthpiece (retained dose). Only a fraction of the deUveied dose will reach the airways, since some of it may be lost into the air or on the face, another fraction will be deposited in the oropharynx, and a small part of the drug will be exhaled (Fig. 2). 

In clinical studies, pulmonary deposition of a drug delivered from a given formulation is generally expressed as a fraction of a reference dose, which may be the 

Nominal dose Metered dose Delivered dose Fine particle dose Retained amount Inhaled dose Exhaled amount Recovered amount  

Dose written on the package label also called labeled dose 

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VII. Relationship Between Pulmonary Deposition and Clinical Effect... 

At appropriate doses, a twofold increase in dose of an inhaled pj-agonist has been shown to result in a statistically significant increase in bronchodilating effect (11). Conversely, it appears to be much more difficult to assess this relationship for inhaled glucocorticosteroids, as an at least fourfold increase in dose is necessary to obtain a statistically significant difference in effect (36). The next paragraphs of this section therefore focus mainly on the relationship between pulmonary deposition and clinical effects of Pj-agonists. 

Most of the work on the relationship between pulmonary deposition and clinical effect has been done with p -agonists, since the immediate effect these drugs is easy to measure. Although it is more difficult to conduct comparative studies with inhaled glucocorticosteroids and anticholinergics, it is very likely that the same concepts also hold true for these drugs, as some studies clearly suggest (99,100). 

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