Suboptimal use of inhaled corticosteroids in children with persistent asthma: inadequate prescription, poor drug adherence, or both?

STUDY
OBJECTIVE: To assess the use of inhaled corticosteroids in children with persistent asthma, including patients' adherence to these drugs and physicians' prescribing patterns, by using a novel drug adherence measure, the Proportion of Prescribed Days Covered (PPDC).
DESIGN: Retrospective analysis. DATA SOURCE: Two administrative claims databases in Quebec, Canada. PATIENTS: Two thousand three hundred fifty-five children aged 5-15 years with persistent asthma who used more than 3 doses/week on average of a short-acting β-agonist during a 12-month period before beginning treatment with inhaled corticosteroids between 1997 and 2005.
MEASUREMENTS AND MAIN RESULTS: The PPDC measure was defined as the total days' supply dispensed divided by the total days' supply prescribed. During the 12-month follow-up period, 20% of the children received only one prescription for inhaled corticosteroids with no prescribed renewals. The mean number of prescriptions (including prescribed renewals) was 5.0, corresponding to only 152 days' supply prescribed. Mean PPDC (drug adherence) was 62.4%. Only 25% of the patients had controlled asthma, based on the use of 3 or fewer doses/week of short-acting β(2)-agonists and absence of moderate-to-severe exacerbations.
CONCLUSION: A large percentage of children with persistent asthma were prescribed intermittent rather than daily inhaled corticosteroids, and patient adherence to these drugs was suboptimal even though children had free access to their drugs. Many of these patients continued to experience poor asthma control. The PPDC adherence measure developed for this study allowed a better understanding of the gap between treatment goals and asthma control.