Equivalent therapeutic ratio of salbutamol given by Turbuhaler^®and Diskus^™

Abstract

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 μ g salbutamol given via either device (double-blind, placebo-controlled). Salbutamol caused a dose-related increase in FEV₁when given by Diskus or Turbuhaler. The improvement in FEV₁was similar regardless of whether salbutamol was given via Diskus or Turbuhaler, at equivalent microgram doses. After a total cumulative dose of 3200 μ g, mean FEV₁for 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.