Objective: To investigate the relative efficacy of three inhalers containing salbutamol: Turbuhaler (TBH), Rotahaler (RH) and Diskhaler (DH).
Methods: A randomized, open, three-way crossover, cumulative dose response study was performed in 20 patients with asthma with mean forced expiratory volume in ls (FEV1) values of 60% of predicted (range 41-90%) and a 27% reversibility in FEV1 (range 15-61%). Four doses of salbutamol were inhaled at 30-min intervals: 50 micrograms, 50 micrograms, 100 micrograms and 200 micrograms by TBH and 200 micrograms, 200 micrograms, 400 micrograms and 800 micrograms by both RH and DH. FEV1 was measured at baseline and 25 min after each dose.
Results: The increases in FEV1 after the first doses (50 micrograms by TBH, 200 micrograms by RH and by DH) were not statistically significantly different (23.6%, 25.1% and 28%, respectively). Based on the parallel shift in the dose response curves, salbutamol TBH was calculated to be 2.4 times as potent as salbutamol RH (95% confidence interval 1.4-3.3) and 2.2 times as potent as salbutamol DH (90% CI 1.3-3.3). Additionally, during dosing with TBH, fewer patients experienced adverse events than during dosing with RH or DH.
Conclusion: Turbuhaler is a twofold more efficient inhaler for salbutamol than Rotahaler or Diskhaler as measured by its bronchodilating effect.