Assessing adherence to inhaled medication in asthma: Impact of once-daily versus twice-daily dosing frequency. The...

This study was aimed at evaluating whether once-daily regimens (od-r) show benefits in adherence when compared to twice-daily (td-r).

Prospective, multicenter, 6-month follow-up study with two visits. The main objective was to compare adherence assessed by the electronic prescription refill rate (EPRR) and by the 10-item Test of Adherence to Inhalers (TAI) in patients with od-r and td-r. Suboptimal adherence was defined as TAI < 50 or EPRR ≤ 80%. The effect of suboptimal adherence on meaningful clinical outcomes and the concordance between EPRR and TAI were also examined.

One hundred and ninety-seven patients (47.3 ± 15.9 years, 65% women) were included and 180 completed the study. TAI score was <50 in 29.8% od-r patients and 46.9% in td-r (p = 0.01) and EPRR was ≤80% in 22.6% and 37.5% respectively (p = 0.02). The correlation between the two methods was moderate (rho = 0.548; p < 0.001). There were no significant differences in FEV₁ (%), symptoms or exacerbations between patients with optimal and suboptimal adherence. During follow-up, five patients (6%) with o-dr and 17 patients (17.7%) with t-dr suffered an exacerbation (p = 0.013). At visit two, 13.1% of the patients with o-dr and 31.3% with t-dr had uncontrolled asthma (p = 0.003), although more patients with o-dr were receiving inhaled corticosteroids in the high-dose stratum (25.8% vs. 11.5%; p = 0.001).

Mean adherence rates were greater with od-r than with td-r, but we did not observe an effect on clinical outcomes.