MONDAY, July 20, 2026 (HealthDay News) -- Insurance denials of first attempts to fill brand-name prescription drugs with no generic competitors increased more than two-thirds from 2018 to 2024, according to a study published online July 9 in the Journal of the American Medical Association.Joseph F. Levy, Ph.D., from Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues estimated formulary-based rejections and subsequent dispensing of initial attempts to fill single-source branded drug prescriptions. The analysis included data from 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) from January 2018 through September 2024.The researchers found that 68.0 percent were paid on the initial fill attempt, while the remainder were rejected for formulary exclusion (14.8 percent) or due to requiring prior authorization or step therapy (e.g., utilization management; 17.2 percent). During the study period, formulary-based rejections increased 67.4 percent (from 24.3 percent in 2018 to 40.7 percent in 2024). Rejections were most common among exchange (48.7 percent) and Medicaid managed care (49.8 percent) versus Medicare prescription drug plans (24.0 percent) and Medicare Advantage prescription drug plans (19.8 percent). Of the attempts that were initially rejected, more than one-third (38.6 percent) ultimately resulted in the rejected molecule being filled within 90 days and nearly half (48.4 percent) resulted in no medication fill in the same therapeutic class within that time frame. Among those ultimately receiving the same molecule or a therapeutic substitute, treatment initiation was delayed an average of 12.2 days after initial rejection."We found that insurance restrictions are increasingly shaping whether and when patients receive medications their clinicians prescribe," Levy said in a statement. "While these policies may help control drug spending, they can also create meaningful barriers to timely treatment and place growing administrative burdens on patients, pharmacists, and clinicians."Abstract/Full Text (subscription or payment may be required).Sign up for our weekly HealthDay newsletter