Aims: To study the effects of electrostatics in a plastic spacer on the lung deposition of salbutamol in asthmatic children.
Methods: Twenty-five children (5-12 years) with mild asthma were given salbutamol hydrofluoroalkane pressurized metered dose inhaler 400 micro g via a 750 ml plastic spacer on separate days. Blood samples were taken for plasma salbutamol at 5, 10, 15 and 20 min after inhalation to measure lung bioavailability as a surrogate for relative lung dose. With immediate inhalation following actuation, a new rinsed spacer (NewRinsed ) was compared with a used spacer after repeated daily use (Used ), a spacer rinsed after repeated use (UsedRinsed ) and a spacer primed with benzalkonium chloride to avoid electrostatics (Primed1). In addition, spacers were evaluated using a 15 s inhalation delay following actuation with primed (PrimedDelay) and rinsed (RinsedDelay) spacers. Data were log transformed and expressed as geometric mean fold difference for the average plasma salbutamol concentration (Cav) over 20 min.
Results: There were significant differences (P < 0.05) in Cav (as geometric mean fold difference and 95% CI) between Primed1 vs NewRinsed 1.92 fold (95% CI 1.15, 3.20) and between Used vs NewRinsed 1.75 fold (1.11, 2.76). There were no significant differences comparing Primed1, Used or UsedRinsed. There were also significant differences (P < 0.05) between Primed1 vs PrimedDelay 2.34 fold (1.31, 4.19), or vs RinsedDelay 3.59 fold (2.15, 5.99); and for Used vs PrimedDelay 2.14 fold (1.24, 3.69), or vs RinsedDelay 3.28 fold (2.13, 5.04).
Conclusions: The relative lung dose of salbutamol from a plastic spacer may differ considerably depending on spacer handling suggesting that nonelectrostatic spacers may be the best way forward.