This retrospective, national, all-payer cohort study examined formulary-based rejections (formulary exclusions, prior authorization, and step therapy) of first-fill attempts for single-source branded drug prescriptions across 1.17 million US patients from January 2018 through September 2024.
32% of 2+ million initial fill attempts were rejected — 14.8% for formulary exclusion and 17.2% for utilization management. Of those rejected, 48.4% received no medication in the same therapeutic class within 90 days, and 38.6% eventually got the originally prescribed molecule; average treatment delay was 12.2 days. Rejections rose 67.4% over the study period (24.3% in 2018 → 40.7% in 2024), with highest rates in Medicaid managed care (49.8%) and exchange plans (48.7%).
Claims data cannot capture clinical outcomes (e.g., disease progression, hospitalizations) resulting from delayed or absent treatment. The study covers only outpatient pharmacy claims and may not reflect prescriptions abandoned before submission. Causal inference is limited by the observational design.
Nearly 1 in 2 patients whose single-source branded drug prescription is initially rejected receives no drug in that therapeutic class within 90 days — clinicians should proactively anticipate denials, document medical necessity early, and have a step-therapy or appeals strategy ready at the point of prescribing.
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