Study objective: To compare the lung delivery of
chlorofluorocarbon-free salbutamol via a pressurized metered-dose
inhaler (pMDI) alone, a pMDI with a small-volume plastic spacer, and a
pMDI with a cardboard tube.
Design: A randomized,
single (investigator)-blind, three-way, crossover study.
Setting: The Asthma and Allergy Research Group, Ninewells
Hospital, University of Dundee, Dundee, Scotland, UK.
Participants: Twelve healthy volunteers aged 16 to 65
Interventions: The subjects were administered
400 μg of salbutamol via a pMDI alone, via a pMDI plus a small-volume
plastic spacer, or via a pMDI plus a cardboard tube.
Measurements and results: Blood samples for plasma
salbutamol concentrations were taken at 5 min, 10 min, and 20 min after
inhalation, to measure lung bioavailability as a surrogate for relative
lung dose. The addition of the plastic spacer resulted in a
significantly higher maximal plasma salbutamol concentration
(Cmax) and average plasma salbutamol concentration
(Cav) than the pMDI used alone. This amounted to a
1.48-fold (32%) difference (95% confidence interval [CI], 1.03 to
2.13) for Cmax and a 1.42-fold (30%) difference (95% CI,
1.01 to 2.00) for Cav. There was no significant difference
in the Cmax or Cav comparing the addition of
the cardboard tube with the plastic spacer or the pMDI alone.
Conclusions: Using a chlorofluorocarbon-free pMDI with a
plastic spacer produced statistically, but not biologically,
significant greater lung delivery of salbutamol. If a spacer is
required for reasons other than increasing delivered drug dose, then
the addition of a readily available cardboard tube will fulfill many of
the required functions with no expense to the