Lung deposition, of inhaled drugs

Other factors that determine the absorbed fraction of inhaled glucocorticoids include the age of the child, as lung deposition of inhaled drugs increases with age (80). Therefore, the minimum effective dose may fall as the child becomes older. Moreover, it is reasonable to hypothesize that systemic absorption will increase once asthma control is established (81). Furthermore, patient adherence and inhaler technique are two factors that can have a large influence on the amount of glucocorticoid inhaled and absorbed. 

Onhoj J, Thorsson L, Bisgaard H. Lung deposition of inhaled drugs increases with age. Am J Respir Crit Care Med 2000 162(5) 1819-22. 

Borgstrom, L., Bengtsson, T., Derom, E., and Pauwels, R. (2000), Variability in lung deposition of inhaled drug, within and between asthmatic patients, with a pMDI and a dry powder inhaler, turbuhaler, Int. J. Pharm., 193,227-230. 

The reality is that it is impossible to measure accurately the lung deposition of inhaled drugs in humans. 

Lung deposition of inhaled drug can be determined by both scintigraphic and pharmacokinetic methods. 

In general, during normal inhalation flow rates, deposition in the oropharynx may be estimated by the impaetion factor AD F (see Fig. 2). In the future, it would be desirable to develop methods for clinieal use in evaluating oropharyngeal, as well as lung deposition of inhaled drugs. 

The alveolar region of the human lung is the ideal region for targeting deposition of inhaled drugs for systemic delivery. 

Biddiscombe, M.F., Melchor, R., Mak, V.H.F., Marriott, R.J., Taylor, A.J., Short, M.D., and Spiro, S.G., The lung deposition of salbutamol, directly labelled with technetium-99m, delivered by pressurized metered dose and drug powder inhalers, Int. J. Pharm., 91 111-121... 

After a brief explanation of the factors governing deposition of aerosol particles in the lung, the common methods of administration of inhalation aerosols have been described. The drugs most frequently delivered by this route are bronchodilators. Correct administration and the use of inhaler accessories, such as spacer devices, enhance the efficacy of inhaled drugs. It is essential that the patient be instructed in the correct use of the devices to optimize the therapeutic effect. 

A spacer, a device that attaches directly to the metered-dose inhaler, should be used because a spacer increases the delivery of the drug to the lungs and decreases deposition of the drug on the oropharyngeal mucosa. 

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