Several in vitro aerosol deposition studies have verified that electrostatic charge, inherent on a plastic valved holding chamber (VHC), can reduce the quantity of drug delivered from a metered-dose inhaler (MDI). This information has spawned the development of at least one metal VHC that is less likely to store electrostatic charge. Interestingly, simply washing the VHC in common liquid household detergent can negate the negative effects of electrostatic charge on a plastic VHC. The ionic detergent coating apparently neutralizes electrostatic charge and improves in vitro drug delivery. We compared in vitro aerosol deposition of fluticasone (Flovent®, GlaxoSmithKline) from a MDI mated to the plastic AeroChamber-Plus™ (Monaghan) VHC treated with detergent to minimized electrostatic forces, and a new metal VHC touted as being “nonelectrostatic” (Votrex™, Pari Respiratory).
The quantity of fluticasone aerosol delivered to a 2“ x 2” fabric filter (Filtrete™, 3M) placed in-line at the VHC mouthpiece was determined by sampling five 110 μg MDI actuations though a constant suction flow of 28.3 L/minute. The mean dose of fluticasone aerosol appearing on this filter (i.e. filter dose) from five runs with each MDI + VHC configuration was normalized per MDI actuation. Fluticasone aerosol was washed from the MDI valve stem, MDI actuator, VHC, and filter with 50% methanol and quantified via HPLC-UV. Differences among the primary outcome were determined using a two-sided Student t test.
The mean normalized filter dose from the detergent coated plastic VHC (91.0 ± 6.9 μg/ actuation) was significantly greater than the filter dose observed for the “nonstatic” metal VHC (81.8 ± 1.2 μg/ actuation; p = 0.0198).
The difference in the quantity of fluticasone aerosol delivered to a 2“ x 2” fabric filter between a detergent coated plastic VHC and a metal VHC is statistically significant but clinically probably irrelevant.
A detergent coated plastic VHC works just as well as a metal VHC advertised as “nonelectrostatic”.
M.J. Asmus, Monaghan Medical Corporation, Grant monies.