Impact of Number of Pharmacies on Dornase Alfa Medication Possession Ratio in Children With Cystic Fibrosis.

Introduction: Medication adherence in cystic fibrosis (CF) has been shown to slow disease progression. Integrated pharmacy services can help increase medication access. The objective of this study was to compare the medication possession ratio (MPR) of dornase alfa between people with cystic fibrosis (PwCF) filling maintenance CF medications at one integrated health system specialty pharmacy (IHSSP) to those filling at multiple pharmacies.

Methods: This retrospective study included PwCF < 18 years of age who were prescribed dornase alfa from January 1 to December 31, 2019. The primary endpoint was the MPR for dornase alfa. Subgroup analyses were performed for those with Medicaid and those with private insurance.

Results: A total of 85 patients were included, with 29 (34.1%) filling all medications at IHSSP and 56 (65.9%) filling at multiple pharmacies. The median MPR of dornase alfa was 0.98 (IQR: 0.76-1) and 0.64 (IQR: 0.34-0.85), (p < 0.001), and ppFEV1 changed by -1% (IQR: -7% to 5%) compared to -5% (IQR: -10% to -1%), (p = 0.03) for the IHSSP group and multiple pharmacies groups, respectively. There was no difference in the number of hospitalizations or length of stay. Improved MPR for PwCF in the IHSSP group was sustained in the Medicaid and private insurance subgroups.

Conclusions: The MPR of dornase alfa was higher, and pulmonary function was maintained in PwCF who were able to use the IHSSP for CF medications. Some insurance policies require specific pharmacies for specialty medications, requiring PwCF to fill prescriptions at multiple pharmacies and potentially worsening adherence and clinical outcomes.