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Side Effects With Inhaled Corticosteroids: HFA

Published in Asthma

Side Effects With Inhaled Corticosteroids: HFAInhaler device can also influence the occurrence of local side effects, mainly through determining the relative amount of drug deposited in the lungs vs the oropharynx. Ideally, a device should maximize the proportion of drug that reaches the lung; higher lung deposition reduces the required dose, and lower oropharyngeal deposition reduces the potential for oropharyngeal side effects. Two types of inhaler device are used by the majority of asthma patients. read

In a pMDI, the drug is dissolved or suspended in a propellant under pressure, and when activated releases a predetermined dose. A pMDI can be used with or without a spacer and can be manually or breath actuated. Use of a spacer device may improve lung deposition and reduce oropharyngeal deposition for patients with poor inhaler technique. The choice of propellant greatly influences drug deposition. Chlorofluorocarbon (CFC) propellants used to be ubiquitous, but concern over their effect on the depletion of ozone in the upper atmosphere has led to their replacement with hydrofluoroalkane (HFA). The use of HFA has had some additional benefits. Because particle sizes of < 5 ^m diameter will reach the lower airways when larger particles are deposited in the oropharynx, and because smaller particle sizes can be achieved with HFA, the use of HFA will likely lead to greater lung deposition, allowing lower doses, and lower oropharyngeal dep-osition. With CFC-based pMDI devices, lung deposition was approximately 10 to 20% depending on the exact device and method of measurement. In contrast, newer HFA-based inhalers are achieving levels of lung deposition 50%.

Dry powder inhalers (DPIs) do not require propellants and use inspiratory efforts to disperse the drug and deliver it to the lungs. Lung deposition with these devices is approximately 15 to 40%, with considerable interdevice variability. Thus, modern pMDI devices that use HFA propellants are at least as good as DPI devices in achieving high lung deposition. It is important to realize that a patient who is having local side effects using one drug/device combination may tolerate the same drug very differently using a different device.
There is a great deal of variability in the reported local side effects of ICS in general and for specific agents. Much of this is due to how side effects are defined and assessed. As many studies compared active agents, without a placebo group, the accuracy of the risk estimation for side effects is often unknown. Nevertheless, the weight of evidence suggests that the risk of local side effects may be higher with FP than with BDP.