An 18-month window is preferable when using dispensing data to study the use of asthma drugs. Still, many adolescents with reported drug use had not purchased any asthma drug in this period. The concordance between parental-reported use and dispensed drugs is higher for adolescents with severe asthma.

In 2016, all prescription drugs included in the reimbursement system in Sweden were made available for children (age 0‐17 years) without any patient fees. Our aim was to estimate the association between this intervention and the dispensing patterns of asthma medications among children. Dispensing data on asthma medications for all children living in Stockholm County during 2014‐2017 were selected to include two years before (January 2014‐December 2015) and after (January 2016‐December 2017) the intervention. In an uncontrolled before and after study, the measures of utilization were as follows: the proportion of children with at least one dispensed asthma medication (prevalence); the number of children initiated on treatment after an 18‐month drug‐free period (incidence); the number of defined daily doses (DDDs) dispensed per child; and the number of children with at least two prescriptions with controller medication (inhaled corticosteroid or leukotriene receptor antagonist) dispensed during 18 months (persistence). In an interrupted time series (ITS) analysis, all measures were included except for persistence. Socio‐economic status was defined using Mosaic data. The prevalence increased after the intervention (from 11.9% to 13.0%). However, the ITS analysis showed a positive trend already before the intervention, and consequently, the increase was not attributable to the intervention. For incidence, similar patterns were observed. There was an increase in dispensed volumes related to the intervention, 46.3 DDDs/child/month before and 51.1 after the intervention (P‐value 0.01). The proportion of children with persistent asthma medication increased from 46.0% to 51.9% in children with low socio‐economic status. In conclusion, the intervention was only modestly associated with changes in the dispensing patterns of asthma medication, with the volume dispensed per child increasing slightly, particularly in children with low socio‐economic status.

This population-based study indicates that adolescents with eczema are undertreated or completely untreated, even those with severe eczema.