Efficacy of low-dose inhaled corticosteroids

Evidence indicates that optimal asthma control can be achieved with lower doses of ICS than were previously used. Recent meta-analyses have demonstrated that doses less than 500 mcg fluticasone per day are very effective in controlling symptoms and improving lung function in people with asthma, and that higher doses confer little additional clinical benefit.^{3, 4}

In one meta-analysis, over 90% of the clinical benefit was achieved at relatively low doses of 250 mcg fluticasone per day.³ The dose-response curve began to flatten out at 100-200 mcg/day and had peaked by around 500 mcg/day. This trend was seen for all major clinical outcome measures, including exacerbations (see Figure 1). A second meta-analysis evaluated the efficacy and safety of ICS and found that the dose-response curve for efficacy was also relatively flat, with very little difference between the efficacy of fluticasone 100 mcg and 1000 mcg daily.⁴

In contrast, the dose-response curve for side effects with ICS is steep beyond a daily dose of around 500 mcg FP.⁴ High doses achieve minimal additional benefit compared with moderate and low doses,³ but significantly increase the risk of adverse effects.⁴ In children, serious adverse events have been reported when higher than recommended doses of ICS have been used, including growth suppression⁵ and significant adrenal suppression.⁶ Studies in adults indicate that the risk of reduced bone density is related to the cumulative dose of ICS treatment.⁷

Figure 1. Dose-response relationship of ICS. The majority of clinical benefit is achieved at low doses, after which the efficacy curve begins to flatten out.³ In contrast, the dose-response curve for side effects increases sharply with higher doses of ICS.⁴