Investigating improving powder deagglomeration via dry powder inhalers at a low inspiratory flow rate by employing add‐on spacers

The aim of this study was to investigate whether small add‐on spacers alone or equipped with a passive deagglomerating component would improve aerosol performances of passive low airflow resistance dry powder inhalers (DPIs) at a low inhalation flow rate. Depositions of beclometasone dipropionate (BDP) and salbutamol sulphate (SS) via the Asmabec Clickhaler and Asmasal Clickhaler at 30 L/min airflow rate in an oropharyngeal model and attached filter were determined. Three add‐on spacers, one with 5.0 cm length, and the other with the same features but incorporating a fine mesh, and the third one with the length of 8.5 cm (long add‐on spacer) were used. Incorporating mesh did not improve the filter dose for SS, and significantly reduced this dose for BDP. The long add‐on spacer was the most efficient spacer as it had minimal effects on the filter doses, also significantly reduced drug depositions in the model. In conclusion, an optimum length of an add‐on spacer is required to minimise oropharyngeal drug deposition via a low airflow resistance DPI at a low inspiratory flow rate without considerable reduction of the respirable dose. Incorporating sieves within add‐on spacers may diminish aerosol performances of the DPIs at low airflow rates. © 2008 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:5212-5221, 2008