Background: Guidelines recommend stepping down inhaled corticosteroids (ICS) in patients with well-controlled asthma. However, no information is available on the index that should be used to predict the outcome of reducing the ICS dose.

Objective: The aim of this study was to investigate the degree of airway responsiveness to adenosine 5' monophosphate (AMP) as an index for deciding whether to reduce ICS dose.

Patients and Methods: The study population comprised 70 patients with asthma that was well controlled with ICS. Patients were treated for a 2-week baseline period with their usual dose of ICS. For the following 12 weeks, patients were treated with ICS at half their previous dose. Bronchial challenge with AMP was performed at the end of the baseline period and after 2 weeks of treatment with a reduced dose of ICS. Concentration-response curves were used to show the provocative concentration of AMP causing a 20% fall (PC₂₀) in forced expiratory volume in 1 second (FEV₁).

Results: A decrease in the PC₂₀ of AMP of at least 1 doubling concentration 2 weeks after reducing the ICS dose was a significant predictor of the failure of dose reduction (P=.0011). In contrast, increased responsiveness to inhaled AMP at baseline did not predict the failure of dose reduction.

Conclusions: Our results suggest that, in patients whose asthma is well controlled with ICS, measurement of the modification in the response to AMP 2 weeks after the dose of ICS was halved is a suitable method for assessing the risk of asthma exacerbation following a reduction in ICS dose.

Key words: Inhaled corticosteroids. Adenosine 5'-monophosphate. Airway responsiveness. Asthma.