Generic and Brand-Name Thyroid Hormone Drug Use Among Commercially Insured and Medicare Beneficiaries, 2007 Through 2016.

Context: Generic drugs account for 9 out of 10 prescriptions dispensed in the United States but for a lower proportion of commonly prescribed thyroid hormone replacement therapies.
Objective: Characterize temporal patterns of generic and brand-name thyroid hormone drug use, including patient and prescriber characteristics associated with brand-name use.
Design and Setting: Cross-sectional longitudinal analysis of national data from a large administrative claims database from January 2007 through December 2016.
Patients: Adults with insurance coverage through commercial, Medicare Advantage, and Medicare Part D health plans.
Main Outcome Measures: Generic and brand-name thyroid hormone drug use.
Results: From 2007 to 2016, the annual number of thyroid hormone treatment pharmacy fills increased from 8,905,836 in 2007 to 11,613,923 in 2016, 73.6% of which were for generic levothyroxine, 23.4% for brand-name levothyroxine, and the remaining for other formulations. Dispensing of generic thyroid hormone drugs increased from 59.8% in 2007 to 84.9% in 2016 and was consistently higher among Medicare Advantage and Medicare Part D when compared with the commercial beneficiary population. For all three beneficiary populations, use of brand-name products was less common among older adults and more common among women and those receiving prescriptions from endocrinologists and was more common among those of white race and with greater household income for the Medicare Advantage and commercial beneficiary populations (P < 0.001).
Conclusions: Brand-name thyroid hormone product use declined from 2007 to 2016 among three large, national insurer beneficiary populations. Although certain patient characteristics were associated with brand-name use, prescriber specialty was the strongest predictor.
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