[Spacer, Aerosol Therapy through Space and Time]

Within this review, results of a literature analysis on the application of spacers with pressurized metered dose inhalers (pMDI) are described and evaluated.

Next to an extensive revision on effects of spacers, the impacts of current guidelines and the conditions for product authorisations on the use of spacers are described which result from the interplay of characteristics from dose inhalers with a spacer.

Spacers are generally useful to avoid coordination problems concerning the actuation of a pMDI at the beginning of an inhalation. Furthermore, in comparison to the pMDI application without a spacer a reduced mouth-throat deposition is applicable to all pMDI spacer combinations. However, some new pMDI release the aerosol in a quality that may not necessarily require a spacer to avoid a high drug deposition in the mouth-throat area as the aerosol quality will not be greatly improved with a spacer. The delivered mass of the active ingredient as well as the aerosol quality released from a spacer vary substantially with the use of different spacers. A change of spacer while using the same dose inhaler can maximally result in a doubling or halving of the quantity of the active ingredient applied. These facts are nowadays considered by the European regulatory agency.

If a spacer application is intended for pMDIs that were developed and approved after 2009, the correspondent SMP (Summary of Product Characteristics) should at least make one specific recommendation for a spacer that should be based upon relevant in vitro data or additional in vivo data. If a different spacer than the recommended one is used, the effectively applied dose cannot be correctly anticipated. This should be considered when choosing a spacer.