Nan Huo1, Li Chen2, Ahmed Ullah Mishuk1, Chao Li1, Richard A Hansen1, Ilene Harris3, Zippora Kiptanui3, Zhong Wang4, Sarah K Dutcher5, Jingjing Qian6. 1. Auburn University Harrison School of Pharmacy, Auburn, AL, USA. 2. Department of Medicine, Indiana University School of Medicine, Indianapolis, IL, USA. 3. IMPAQ International LLC, Columbia, MD, USA. 4. Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA. 5. Office of Surveillance and Epidemiology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA. 6. Auburn University Harrison School of Pharmacy, Auburn, AL, USA. jzq0004@auburn.edu.
Abstract
PURPOSE: Generic levothyroxine has been approved and available since 2004 but its substitution remains controversial. Therefore, the objective was to examine patterns of and identify factors associated with initiation and substitution of generic levothyroxine treatment. METHODS: This was a retrospective observational study, including new users of brand and generic levothyroxine in 2013-2015 Medicare (n = 15,877) or 2011-2012 Medicaid (n = 9390) administrative claim databases. The primary outcomes included (1) generic levothyroxine initiation, and (2) among brand-new users, generic levothyroxine substitution in 12 months. The factors associated with generic levothyroxine initiation and substitution were measured. RESULTS: Among all levothyroxine new users, Medicare beneficiaries had a higher proportion of generic levothyroxine initiation than Medicaid beneficiaries (66.40% vs. 44.04%, respectively). Medicare beneficiaries' demographic factors, and health service utilizations were associated with generic levothyroxine initiation. Medicaid beneficiaries who were male and residing in the northeast region and rural areas were more likely to initiate generic levothyroxine. Among brand levothyroxine new users, the generic substitution rate was higher in the Medicare than the Medicaid cohort (18.26 vs. 3.88%). Medicare brand levothyroxine new users' demographic factors and health service utilizations were associated with generic levothyroxine substitution. Medicaid brand levothyroxine new users who were residing in the northeast region, with more prior hospitalization, and initiating a lower dosage of brand levothyroxine, had higher rates of generic substitution. CONCLUSION: Patient demographic factors and health service utilizations are associated with generic levothyroxine initiation and substitution. Educational outreach programs targeted to increase generic levothyroxine use and prescription savings should be tailored based on different patient populations.
PURPOSE: Generic levothyroxine has been approved and available since 2004 but its substitution remains controversial. Therefore, the objective was to examine patterns of and identify factors associated with initiation and substitution of generic levothyroxine treatment. METHODS: This was a retrospective observational study, including new users of brand and generic levothyroxine in 2013-2015 Medicare (n = 15,877) or 2011-2012 Medicaid (n = 9390) administrative claim databases. The primary outcomes included (1) generic levothyroxine initiation, and (2) among brand-new users, generic levothyroxine substitution in 12 months. The factors associated with generic levothyroxine initiation and substitution were measured. RESULTS: Among all levothyroxine new users, Medicare beneficiaries had a higher proportion of generic levothyroxine initiation than Medicaid beneficiaries (66.40% vs. 44.04%, respectively). Medicare beneficiaries' demographic factors, and health service utilizations were associated with generic levothyroxine initiation. Medicaid beneficiaries who were male and residing in the northeast region and rural areas were more likely to initiate generic levothyroxine. Among brand levothyroxine new users, the generic substitution rate was higher in the Medicare than the Medicaid cohort (18.26 vs. 3.88%). Medicare brand levothyroxine new users' demographic factors and health service utilizations were associated with generic levothyroxine substitution. Medicaid brand levothyroxine new users who were residing in the northeast region, with more prior hospitalization, and initiating a lower dosage of brand levothyroxine, had higher rates of generic substitution. CONCLUSION:Patient demographic factors and health service utilizations are associated with generic levothyroxine initiation and substitution. Educational outreach programs targeted to increase generic levothyroxine use and prescription savings should be tailored based on different patient populations.
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