Original Investigation 

Formulary-Related Insurance Denials of Single-Source Branded Drugs in the United States

Joseph F. Levy, G. Caleb Alexander, Boris Vabson, et al

JAMA Published Online: July 9, 2026

doi: 10.1001/jama.2026.8702

Key Points

Question  How frequently are prescriptions rejected because of insurance formulary restrictions in the United States, and how often are the rejected medicines ultimately dispensed?

Findings  In this longitudinal, all-payer cohort study of approximately 1.17 million individuals attempting to fill more than 2 million single-source branded drugs between 2018 and 2024, 32.0% were rejected. Once rejected, 38.6% of individuals obtained the prescribed drug, 13.0% received a medication in the same therapeutic class, and nearly half (48.4%) received no medication in the same therapeutic class within 90 days.

Meaning  Formulary rejections are becoming more common over time, across all insurance, and often prevent patients from obtaining initially prescribed treatments, highlighting trade-offs between cost and access to medicines.

Abstract

Importance  Formulary exclusions and drug utilization management, including prior authorization and step therapy, reduce drug spending but may limit timely treatment access.

Objective  To estimate formulary-based rejections and subsequent dispensing of initial attempts to fill single-source branded drug prescriptions.

Design, Setting, and Population  Retrospective, national, all-payer cohort study using IQVIA Formulary Impact Analyzer, which represents anonymized, patient-level, adjudicated US outpatient pharmacy claims, from January 2018 through September 2024. The study focused on 1.17 million individuals attempting to fill 2 million single-source branded drug prescriptions for the first time.

Exposure  Attempt to fill a single-source branded drug prescription for the first time.

Main Outcomes and Measures  The primary outcomes were (1) rejection for formulary exclusion or utilization management (prior authorization or step therapy) of an initial prescription fill attempt and (2) failure of dispensing of the rejected molecule or another member of the same therapeutic class within 90 days of the initially attempted fill.

Results  Among more than 2 million initial fill attempts (commercial insurance, 0.84 million; stand-alone Medicare prescription drug plan, 0.40 million; Medicare Advantage prescription drug plan, 0.39 million; Medicaid fee-for-service, 0.21 million; Medicaid managed care, 0.10 million; health insurance marketplace [exchange] plan, 0.06 million), 68.0% were paid on the initial fill attempt, while the remainder were rejected for formulary exclusion (14.8%) or rejected due to requiring prior authorization or step therapy, ie, utilization management (17.2%). Formulary-based rejections increased 67.4% over the time frame examined, from 24.3% (2018) to 40.7% (2024), and rejections were most common among exchange (48.7%) and Medicaid managed care (49.8%) compared with Medicare prescription drug plans (24.0%) and Medicare Advantage prescription drug plans (19.8%). Of the 32% of attempts that were initially rejected, 38.6% ultimately resulted in the rejected molecule being filled within 90 days and nearly half (48.4%) resulted in no medication fill in the same therapeutic class within that time frame. Treatment initiation was delayed an average of 12.2 days (SD, 17.8 days) after initial rejection among those ultimately receiving the same molecule or a therapeutic substitute.

Conclusions and Relevance  Among this large, diverse sample of individuals in the United States, formulary rejections were frequent and often resulted in delayed or absent treatment, highlighting trade-offs between cost and access to medicines.