Regular short-acting β₂-agonist use over two weeks does not increase diurnal variation or induce tolerance during...

Asthma diagnosis in Finnish primary care relies heavily on home peak expiratory flow (PEF) monitoring. A distinctive feature of the Finnish PEF monitoring protocol is the assessment of bronchodilator response (BDR) twice daily.

Our aim was to determine whether consistent short-acting β₂-receptor agonist (SABA) use leads to increased diurnal PEF variation or tolerance to its bronchodilator effects.

We retrospectively studied 108 steroid-naive patients who had completed home PEF monitoring using two different protocols: in Protocol A patients used salbutamol 200 µg or terbutaline 500 µg twice daily only during the second week, while in Protocol B they used SABA during both weeks. Mean PEF, diurnal variation, BDR, and the number of instances of significant diurnal variation and BDR were compared between the first and second weeks of monitoring for both groups.

Mean PEF values remained stable, with no significant differences between the first and second weeks in either protocol. Similarly, no significant differences were observed in relative diurnal variation, absolute diurnal variation, or in the number of occurrences of significant diurnal variation. Likewise, no changes were found in relative BDR, absolute BDR, or in the frequency of significant BDRs during the two-week SABA use.

We conclude that regular SABA use for one or two weeks does not lead to decreased PEF, increased diurnal variation, or tolerance to its bronchodilator effects. However, such adverse effects cannot be ruled out with longer use. Regular twice-daily BDR assessment during two-week home PEF monitoring appears safe and appropriate.