Rates of, and factors associated with, switching among generic levothyroxine preparations in commercially insured American adults
Open accessAbstract
Importance Some practice guidelines warn against generic L-thyroxine preparation switching.Objective To examine the rates of generic L-thyroxine preparation switching within one year of initiating L-thyroxine, and to examine factors associated with switching.Design and setting Retrospective study using national data from a large administrative claims database from January 2008 through November 2018.Patients Medicare or commercially insured adults (≥18 years) who filled a generic L-thyroxine preparation.Main outcome measures At least one switch from one generic L-thyroxine preparation to another within 1 year of L-thyroxine initiation defined by prescription fills.Results From January 2008 to November 2018, we included 483,390 patients who initiated generic L-thyroxine: mean (SD) age was 61.4 years (15.2), 75.2% were female, 72.6% were white. Within 1 year of initiating therapy, 98,013 (20%) switched to another L-thyroxine generic preparation at least once. In a multivariate logistic regression analysis, factors associated with switching included the number of pharmacies visited to fill L-thyroxine (>2 vs 1 adjusted OR [aOR] 7.15, 95% confidence interval [CI] 6.97-7.34), age ≥75 vs. <45 years (aOR 1.29, 95% CI 1.26-1.33), history of thyroid surgery (aOR 1.22, 95% CI 1.13-1.31), and first L-thyroxine fill date in 2018 vs. 2008 (aOR 3.32, 95% CI 3.14-3.51).Conclusions and relevance One in five patients switched among generic L-thyroxine manufacturers within one year of treatment initiation. Generic L-thyroxine switching occurred more often when more pharmacies were used to fill L-thyroxine. Given existing guideline recommendations, additional studies should clarify the impact of generic L-thyroxine switching on thyroid hormone values.
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As reported in US studies, 20% of patients switch to another LT4 generic preparation at least once within the first year of initiating therapy, and a change in the LT4 preparation is the leading cause (56.0%) of the TH level fluctuation observed in LT4-treated patients.
“As reported in US studies, 20% of patients switch to another LT4 generic preparation at least once within the first year of initiating therapy, and a change in the LT4 preparation is the leading cause (56.0%) of the TH level fluctuation observed in LT4-treated patients (118, 119).”
From Levothyroxine: conventional and novel drug delivery formulations. (2023) · cites this paper as [119]
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Levothyroxine: conventional and novel drug delivery formulations.
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- Authors
- Brito, J. P., Deng, Y., Ross, J. S., Choi, N. H., Graham, D. J., Qiang, Y., Rantou, E., Wang, Z., Zhao, L., Shah, N. D., & Lipska, K. J.
- Affiliations
- Mayo Clinic (US)
- Yale New Haven Hospital (US)
- United States Food and Drug Administration (US)
- Delta Air Lines (United States) (US)
- Corresponding author
- Brito, Juan P.
- ORCID
- Venue
- Endocrine
- Published
- 2022-02-02
- Volume
- 76
- Issue
- 2
- Pages
- 349-358
- ISSN
- 0969-711X (ISSN-L)
- 1559-0100
- PMC
- PMC9210352
- OpenAlex
- W4210432149
- Cited by
- 4
- References
- 10
- Citations by year
- 2024: 1 · 2023: 1 · 2022: 2
- FWCI
- 0.80
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- Endocrine (publishedVersion)
- PubMed (publishedVersion)
- PubMed Central (acceptedVersion)
- Funders
- U.S. Food and Drug Administration (U01 FD004585, U01FD005938)
- Agency for Healthcare Research and Quality (R03 HS025517, U19 HS024075, R01 HS025402, R01 HS025164, R01HS022882)
- National Institute on Aging (K23AG048359)
- National Heart, Lung, and Blood Institute (R56HL130496, R01HL131535)
- Topics
- Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Pharmaceutical Economics and Policy
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Healthcare Policy and Management
- Keywords
- levothyroxine, generic drug switching, thyroid hormone replacement, pharmaceutical manufacturers, commercially insured adults, Medicare, pharmacy visits, age, prescribing guidelines
- MeSH terms
- Adult, Aged, Female, Medicare, Humans, Male, Middle Aged, Retrospective Studies, Thyroid Hormones, Thyroxine, United States, Drugs, Generic
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