Airway hyperresponsiveness (AHR) to adenosine 5'-monophosphate (AMP) occursin patients with asthma and COPD. In patients with asthma, but not with COPD, AHR to AMP is reduced by long-term treatment with inhaled steroids. In addition recently it has been shown that one single dose of fluticasone attenuates, after 2 h, AHR to AMP in mild asthma. The aim of this study was to establish whether or not this rapid protective effect of inhaled fluticasone occurs in patients with COPD.

We therefore compared changes in AHR to AMP after one single dose of inhaled fluticasone (1000 μg) in 13 non smokers with mild asthma and in 14 smokers with mild-moderate COPD. The study was conducted according to a randomized, double-blind, placebo-controlled protocol. Patients were in stable clinical condition and no inhaled/oral steroid was used in the last month before the study. Inhaled B₂-agonists were discontinuated at least 24 h before the study. In each study day the patients, underwent bronchial challenge with AMP, 2 hours after inhalation of either placebo or fluticasone.

The mean PC₂₀ AMP significantly increased from 15.2 ± 8.04 mg/ml after placebo to 79.10 ± 119.8 mg/ml after fluticasone (P<0.001) in asthmatics, whereas no significant change was observed in COPD patients their PC₂₀ AMP being 79.3 ± 14.7 mg/ml and 93.2 ± 31.3 mg/ml after placebo and fluticasone respectively (P=NS).

A single dose of inhaled fluticasone rapidly improves AHR to AMP in asthmatics but not in patients with COPD. This may provide a convenient way by which provocation challenge with inhaled AMP may be useful in discriminating asthma from COPD.