Spacer |


If a pMDI is to be used in children it must be developed for use together with a specific appropriate spacing device. Differences between inhalation devices can cause several fold changes in efficacy as well as systemic bioavailability. Effective spacers improve lung dose and facilitate coordination between actuation and inhalation. Also, spacers decrease the amount of medicinal product deposited in the mouth and pharynx and subsequently swallowed. Spacers perform differently with different active substances and formulations. The distribution and response to an active substance cannot be assumed to be equivalent if a different spacer is used or if a different pMDI is used with the same spacer. The development of a pMDI should always include the testing of at least one specific named spacer for use with the particular pMDI containing a particular active substance. The behaviour of the spacer will depend on the volume and material of the holding chamber, on the electrostatic properties of the internal surface of the chamber and on the way in which the device is used. Hence the in vitro testing should be carried out by preparing the spacer and setting up the apparatus in a clinically relevant manner which may influence the performance of the product, for example, inserting a time delay between actuation and inhalation to simulate tidal breathing and washing/preparation of the spacer before and during use according to the instructions of the manufacturer of the spacer.
Professor Hans Bisgaard • Copenhagen • Denmark •