Relative efficacy of three different inhalers containing salbutamol in patients with asthma

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 1s (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 μg, 50 μg, 100 μg and 200 μg by TBH and 200 μg, 200 μg, 400 μg and 800 μg 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 μg by TBH, 200 μg 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. Received: 15 February 1996/Accepted in revised form: 16 February 1996