A prescription arriving at the pharmacy does not guarantee that an insurer will pay for it on the first try. For brand-name medicines without generic competitors, that barrier became markedly more common across a six-year study period. The result was not only paperwork: many patients waited for treatment or never filled a drug in the same class.
The study followed first attempts at the pharmacy counter
Researchers examined pharmacy claims for people trying to fill a single-source branded medicine for the first time. These are brand-name drugs sold without a generic competitor, a group in which the insurer’s formulary decision can carry particular weight because a chemically equivalent lower-cost version is unavailable.
The Johns Hopkins Bloomberg School of Public Health summary says the analysis covered more than 2 million prescription attempts by 1.17 million people from January 2018 through September 2024. Claims represented commercial insurance, Medicare drug plans, Medicaid and Affordable Care Act marketplace coverage. The study was published online in JAMA on July 9, 2026.
Rejections climbed from 24.3% to 40.7%
The share of initial attempts rejected for formulary reasons rose 67.4% over the period, from 24.3% in 2018 to 40.7% in 2024. In the full sample, 68% were paid on the first attempt. The other 32% were rejected because the medicine was excluded from the plan’s formulary or because utilization-management rules applied.
The peer-reviewed study record separates those barriers into 14.8% rejected for formulary exclusion and 17.2% rejected for prior authorization or step therapy. Prior authorization requires the insurer to approve coverage before payment, while step therapy generally requires a patient to try another treatment first. A rejection at this stage is therefore not always a permanent refusal, but it interrupts the original fill.
Nearly half had no same-class fill within 90 days
Among initially rejected attempts, 38.6% eventually resulted in the originally prescribed medicine being dispensed within 90 days. Another share received an alternative from the same therapeutic class. Still, 48.4% had no record of either the rejected medicine or a same-class alternative being filled within that window.
For patients who eventually received the original medicine or a same-class substitute, treatment began an average of 12.2 days after the first rejection. The JAMA investigation describes those results as evidence of a trade-off: formulary controls may restrain spending, yet frequent rejections can delay or prevent access to prescribed treatment. The study did not determine the clinical effect of each delay.
Coverage type and drug class changed the odds
Initial rejection rates were not uniform. Marketplace plans and Medicaid managed-care plans approached a 50% rejection rate in the study, while stand-alone Medicare drug plans and Medicare Advantage drug plans had lower rates. Commercial plans and Medicaid managed care showed some of the steepest increases in utilization-management restrictions over time.
Therapeutic categories also varied widely. Incretin-based weight-loss treatments, including GLP-1 receptor agonists and related drugs, had an initial rejection rate of about 85%, while oral anticoagulants were rejected far less often. Those comparisons reflect the medicines, plans and time captured in the claims database; they do not predict the outcome of a particular prescription.
Claims data reveal access barriers but not every outcome
The database recorded adjudicated outpatient pharmacy claims from participating pharmacies. It could miss a medicine paid for through another channel or filled somewhere outside the data network. The researchers also could not always identify the precise rejection reason or determine whether a patient received a clinically appropriate treatment from a different therapeutic class.
Because the analysis begins when a prescription reaches the pharmacy, it cannot measure drugs clinicians chose not to prescribe after seeing formulary restrictions. It also does not establish that every rejected drug was the best treatment or that every utilization rule was inappropriate. Its narrower finding is still consequential: the payment barrier attached to first fills became much more common, and a large share of rejected attempts were followed by no same-class dispensing within three months.
An initial denial starts a process rather than ending one
Patients and prescribing offices can ask the plan or pharmacy for the exact rejection reason, determine whether prior authorization or step therapy is required, and review covered alternatives. Plans provide appeal procedures, and urgent medical circumstances may qualify for faster review. Records of the prescription, denial notice, prior treatments and clinician’s rationale can support that process.
For marketplace coverage, HealthCare.gov explains internal appeals and external review rights. Medicare, Medicaid and employer plans use their own procedures and deadlines, so the controlling plan documents matter. The new study shows why those procedures are no longer edge cases for single-source branded drugs: the first barrier now appears in a substantial portion of attempts across major insurance markets.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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