Formulary-related insurance denials of single-source branded drugs in the US

A new study published in JAMA has found that insurance formulary rejections of single-source branded drugs are common in the United States and often leave patients without timely access to prescribed medicines.

Drawing on a large and diverse national sample, researchers found that formulary rejections occurred frequently and, in many cases, resulted in treatment being delayed or never received at all. The findings underscore the persistent tension between efforts to control drug spending and patients’ ability to obtain the medications their clinicians prescribe.

Single-source branded drugs—medications available from only one manufacturer with no generic equivalent—can be particularly vulnerable to access problems when insurers decline to cover them under their formularies, the lists of drugs a health plan agrees to pay for.

The authors say the results highlight the real trade-offs patients face between cost and access, and point to the need for closer scrutiny of how formulary decisions affect the people who depend on these treatments.

The study was led by corresponding author Joseph F. Levy, PhD, of Johns Hopkins University. Additional details, including author affiliations, conflict of interest disclosures, and funding sources, are available in the full article (doi:10.1001/jama.2026.8702).