AN IN-VITRO EVALUATION OF VARIOUS SPACER DEVICES FOR METERED-DOSE INHALERS USING THE TWIN-IMPINGER

Spacer devices are a useful tool in inhalation therapy with metered-dose inhalers (MDI). Various spacers with different shapes and sizes are currently on the market. This study intends to evaluate nine commercial spacers for use with MDIs. These devices were tested in combination with two different cromolyn-sodium MDIs. The assessment has been carried out using the Twin Impinger. The fractions of the dose remaining in actuator and spacer and the fractions delivered to stage 1 (D-50% > 6.4 mu m) and stage 2 (D-50% < 6.4 mu m) of the Twin Impinger were calculated and compared to a control experiment without spacer. Deposition in stage 1 is significantly reduced for all spacers. The differences indicated that the spacers are not equivalent. Some spacers increase the fraction of the dose delivered to stage 2 whereas others strongly reduce this fraction. This effect appears to be independent of spacer volume but depends on spacer and valve construction.