Equivalent therapeutic ratio of salbutamol given by Turbuhaler and Diskus

Some inhalers have been claimed to give better deposition, resulting in higher efficacy. In a previous study we did not find any evidence of different potency of salbutamol given either via pMDI or Turbuhaler. The aim of the present study was to compare the efficacy and safety of salbutamol given via Diskus or Turbuhaler. Twenty-five asthmatics with step-wise reversible airflow obstruction (total reversibility of at least 15%) were included in a randomized, double-dummy, placebo-controlled cross-over study. On each study day, the patients were given placebo repeatedly, or cumulative doses of 200, 400, 800, 1600 and 3200 microg salbutamol given via either device (double-blind, placebo-controlled). Salbutamol caused a dose-related increase in FEV1 when given by Diskus or Turbuhaler. The improvement in FEV1 was similar regardless of whether salbutamol was given via Diskus or Turbuhaler, at equivalent microgram doses. After a total cumulative dose of 3200 microg, mean FEV1 for Diskus was 2.46 l (change from baseline of 20.5%), for Turbuhaler 2.50 l (change from baseline 24.6%) and for placebo 2.11 l (3% change from baseline). After correcting for different baseline differences, the percentage difference between Diskus and Turbuhaler was -1.8% (P = 0.2). Systemic effects (potassium and heart rate) did not differ between Diskus or Turbuhaler. We conclude that the efficacy of salbutamol given at equivalent microgram doses, as well as side-effects, are comparable when the drug is given via Diskus or Turbuhaler. The present data shows that salbutamol given by these devices have similar therapeutic ratios.