2002 Abstracts
COMPARISON OF PERFORMANCE OF TWO VALVED HOLDING CHAMBERS (VHCs) WITH DELAY BETWEEN METERED DOSE INHALER ACTUATION AND USEJolyon P. Mitchell Ph.D, Sara-Lou Bates, Cathy C. Doyle B.Sc, and Mark W. Nagel HB.Sc
Trudell Medical Aerosol Laboratory, London, Canada
VHCs are recommended for use with pressurized metered-dose inhalers (pMDIs) for those patients who may delay the onset of inhalation after pMDI actuation. A draft Canadian (CAN/CSA) Standard on Spacers and Holding Chambers (expected publication, 2002) has recommended that in vitro performance testing be undertaken with a 2 s delay to simulate this behavior. We compared the performance of two similar sized VHCs (AeroChamber Plusª , Monaghan Medical Corp., Plattsburgh, NY and PrimeAire®, Thayer Medical, Tucson, AZ) (n = 4 devices/group) with a 2 s delay between actuation and sampling into an Andersen 8-stage cascade impactor equipped with USP Induction port. Each VHC was washed with an ionic detergent, rinsed and drip-dried to minimize the influence of electrostatic charge. The impactor was operated at 28.3 ± 0.5 L/min in accordance with <601> of the US Pharmacopeia, representative of the inspiratory flow rate range seen in adult patients. A purpose-built apparatus enabled the delay interval to be reproduced to within 0.1 s. 5-doses of fluticasone propionate (FP) (Flovent® 110, GSK Canada Inc.) were initially delivered from a pre-primed and shaken pMDI canister at 30-s intervals via the VHC into the induction port of the impactor. The induction port and stages of the impactor and the VHC were subsequently assayed for FP by HPLC – UV spectrophotometry.
Measurements of fine particle dose (FPD – particles < 4.7 mm aerodynamic diameter) and total emitted dose (TED) are summarized in the table. Fine particle fraction (FPF) is the ratio of FPD/TED, expressed as a percentage.
| PrimeAire® VHC |
AeroChamber Plusª VHC |
|
| TED (mg) | 14.2 ± 1.8 | 31.2 ± 5.4 |
| FPD (mg) | 13.3 ± 1.9 | 30.1 ± 5.3 |
| FPF (%) | 93.6 ± 2.7 | 96.3 ± 0.6 |
mean ± S.D
As expected, both types of VHC largely eliminated coarse particles, with similar values of FPF for this formulation (p = 0.10). However, both TED and FPD from the AeroChamber Plus? VHCs were greater than their equivalent values from the PrimeAire® VHCs [un-paired t-test, p< 0.001].
The introduction of
a delay to mimic the uncoordinated patient resulted in significantly reduced
output from the PrimeAire® VHC. The clinical
significance of these results remains to be explored.
