Introduction: Although drug shortages for outpatient chronic conditions commonly occur, population-level data on how they impact patients' ability to refill prescriptions is scarce. We sought to identify distinct patterns of refill adherence following drug shortages and patient- and prescription-level factors associated with adherence trajectories reflecting potential shortage-related treatment disruption.
Methods: We retrospectively analyzed panel data assembled from 2017 to 2020 Veterans Health Administration (VHA) electronic health record data. Patients were included if they were baseline users of medications subject to a shortage within VHA. Group-based trajectory modeling was applied to users' monthly proportion of days covered (PDC) values from 6-months before to 6-months after the reported drug supply chain disruption. Patient demographics and medication characteristics were compared between identified trajectory groups using multivariable logistic regression.
Results: Among 1.5 million episodes of medication use (representing 1.3 million unique Veterans) for 29 medications in shortage in VHA, 6.3% were for female patients and the mean age was 66.4 ± 12.8 years. A 4-group trajectory model had the best fit: High Adherence (69.2% of observations), Moderate Adherence (14.1%), Potential Shortage-Related Disruption (8.5%), and Pre-Shortage Disruption (8.3%). Drug characteristics (drug class, number of manufacturers) were more strongly associated than patient characteristics with having Potential Shortage-Related Treatment Disruption vs. High Adherence.
Conclusions: We identified 4 trajectories of refill adherence for medications subject to VHA drug shortages, with 8.5% of users of affected drugs exhibiting a trajectory consistent with shortage-related treatment disruption. Drug characteristics may modify whether drug shortages lead to treatment disruption in VHA.
Keywords: drug shortage; drug supply chain; medication adherence; treatment disruption; veteran.
The frequency of drug shortages due to supply chain issues has increased dramatically over the past decade, but evidence for their impact on patient care is limited. Using a sample of prescription data from 1.3 million patients from the Veterans Health Administration (VHA), we examined trends in continuous medication use for 29 outpatient drugs that experienced shortages between 2017 and 2020. Although most veteran patients continued to receive their medications consistently throughout the shortages, 8.5% potentially experienced disruption in their prescription fills that lined up with the timing of the shortages. Disruptions were more marked for drugs with fewer manufacturers, while demographic factors were largely unrelated. These results show that further action is needed to protect patients' access to outpatient medications in the event of shortages.
© 2026 The Author(s). Pharmacoepidemiology and Drug Safety published by John Wiley & Sons Ltd.