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pMDIs produce aerosols that leave the device at high speed. This means that the patients have got very short time to inhale the dose. This can make the coordination of actuation and inhalation difficult, resulting in considerable oropharyngeal (mouth and throat) drug deposition and variability in lung dose. The use of holding chambers slows the aerosol cloud, thereby eliminating the need for coordination of actuation and inhalation. As a result, oropharyngeal deposition is reduced, and hence the therapeutic ratio is improved. The combination of pMDI and holding chamber provides a particularly useful means of drug delivery in children, who are often unable to use a pMDI correctly (Bisgaard, 1995; Bisgaard et al, 2002; Janssens, 2001).
Bisgaard H. Delivery of inhaled medication to children. J Asthma 1995;34:443-67. Bisgaard H, et al. Spacer devices. In: Drug delivery to the lung. Bisgaard H, O’Callaghan C, Smaldone GC, eds. Marcel Dekker, New York; 2002;389-420. Janssens HM. Aerosol delivery in young children. Thesis. Erasmus University, Rotterdam, The Netherlands. 2001. |
