Population characteristics, use, and spending on sole-source, off-patent drugs among commercial insurance members in the United States—An analysis of outpatient claims data at a single health plan

Introduction: Large price increases of off-patent drugs with one manufacturer are common in the US due to the monopoly power afforded to single manufacturers. Little is known about the patients using these drugs, including the prevalence of use or the cost to patients and health systems. Objective: To analyze patient characteristics, prevalence of use, and spending on sole-source off-patent drugs among a commercially-insured population in 2017. Methods: We evaluated the prevalence of use of sole-source off-patent drugs overall and use of sole-source off-patent drugs with large price increases according to member demographic characteristics and medical conditions. We calculated total and out-of-pocket spending per member and total and out-of-pocket spending on all sole-source off-patent drug fills. We evaluated by insurance status, a drug's history of a large price increase, and drug classification. We determined the top ten sole-source off-patent drugs by highest overall spending. Results: Use of sole-source off-patent drugs was observed in 9% of patients. Use was more common among adults with chronic medical conditions, whereas use of drugs with large price increases was rare. Out-of-pocket spending was highest among Medicare-insured patient. Insulin accounted for a disproportionate share of total spending. Conclusion: Sole-source off-patent drug use among patients with chronic medical conditions was common, suggesting these populations are vulnerable to future price increases. Policies that promote manufacturer competition and limit out-of-pocket spending for these drugs, particularly insulin, are likely to benefit patients.