Author's response

The correspondents raise an important point regarding the drug–device interaction and their references support their concern.1 Indeed, there can be a significant interaction between the delivery device and the drug that can affect systemic delivery to the body.2 Our comment was directed at the amount coming out of the metered-dose inhaler to the mouth and that the total fraction is decreased with a spacer. There are many factors, as summarized in our review, that ultimately affect the amount of drug that is systemically absorbed from the lung or the gastrointestinal tract that can modify the amount available systemically in the body.

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