For instance, in the Turbuhaler DPI, a reduction in peak inhaled flow rate from 60 to 30 l min −1 was shown to result in a reduction in lung deposition from 27% to 14% of the dose. All DPIs exhibit some degree of inhaled flow rate dependence, with forceful (fast) inhalation tending to give higher lung deposition than more gentle (slow) inhalation. In order to disperse the powder as efficiently as possible, and hence to maximize lung deposition, it may be necessary for patients to inhale as forcefully as possible via the DPI, and some patients may be either unable or unwilling to do this. However, this second advantage is closely linked to a disadvantage. Second, all currently marketed models are breath-actuated, and patients find them easier to use correctly than pMDIs.
However, DPIs tend to be more expensive than pMDIs, and this may limit their use, especially in developing countries.ĭPIs have two major advantages over pMDIs. In particular, combination products in DPIs containing a long-acting β-agonist and a corticosteroid (e.g., Advair Diskus and Symbicort Turbuhaler) have been very successful. It is interesting to note that the major pharmaceutical companies with an interest in inhaled asthma and COPD drugs appear to be prioritizing the DPI over reformulated HFA pMDIs products. The anticipated expansion of the generics market for inhaled asthma and COPD drugs is likely to result in a number of these novel DPIs reaching the market. A further 20–30 DPIs were also known to be in development. The high lung deposition from the Flowcaps and Eclipse DPIs probably reflects the properties of the formulation as much as the DPI.īy the end of 2004, at least 16 DPIs had been marketed in different areas of the world for asthma and COPD therapy, involving a range of unit-dose, multiple unit-dose, and reservoir systems. Mean percentage of the dose deposited in the lungs from 14 dry powder inhalers (DPIs), obtained in scintigraphic studies.
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