Background: Monodisperse salbutamol inhalers were compared to select the optimal mass median aerodynamic diameter: 4.0, 5.0 or 6.0 microm.
Methods: Fifteen mild asthmatic patients participated. In all a FEV(1)-response of >12% (vs. baseline) or >200 mL after inhalation of 200 microg salbutamol was measured. Each patient was studied four times with intervals of 1 week (three active and one placebo inhaler). First, 10 microg salbutamol was administered, followed by 10, 20, and 40 microg, resulting in cumulative doses of 10, 20, 40, and 80 microg salbutamol. The FEV(1) and other lung function parameters were assessed at baseline and 30 min after inhalation of each consecutive dose. Five minutes later a next inhalation was given.
Results: The 4.0- and 5.0-microm droplets did not differ from placebo (p = 0.502, p = 0.127), but the 6.0-microm droplets differed significantly (p = 0.003). The difference between 6.0-4.0 microm droplets was significant (p = 0.020), but not between the 6.0-5.0 microm droplets (p = 0.129). The FEV(1) increase after 80-microg salbutamol for the 6.0-microm droplets was 243 +/- 144 mL.
Conclusions: The study showed that the 6.0-microm droplets differed from the others in terms of FEV(1)-improvement, and hence, are the most efficacious of the three evaluated.