Provider and Patient Determinants of Generic Levothyroxine Prescribing: An Electronic Health Records-Based Study

Generic levothyroxine initiation and substitution among Medicare and Medicaid populations: a new user cohort study

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.

Comparison of Incident Cardiovascular Event Rates Between Generic and Brand l-Thyroxine for the Treatment of Hypothyroidism

OBJECTIVE

To determine whether levothyroxine (L-T4) preparation (generic vs brand) affected hospitalization for cardiovascular events.

PATIENTS AND METHODS

We performed a retrospective analysis using a large administrative claims database, OptumLabs Data Warehouse, creating two 1-to-1 propensity score-matched cohorts initiating generic or brand L-T4. Patients were followed for a mean of 1.0±1.2 years (range, 0-9.3 years). We included 87,902 propensity score-matched patients (43,951 patients per cohort) initiating generic or brand L-T4. Variables included in matching were age, sex, race/ethnicity, residence region, selected comorbidities, and Charlson-Deyo comorbidity score. Patients with previous use of any thyroid preparation, amiodarone, or lithium were excluded. Primary outcomes were the event rates for hospitalizations for incident atrial fibrillation, myocardial infarction, congestive heart failure, or stroke.

RESULTS

In the generic L-T4 cohort, 35,242 (80.2%) were women and 7327 (16.7%) were 65 years of age or older; in the brand L-T4 cohort, 34,633 (78.8%) were women and 8092 (18.4%) were 65 years of age or older. We found no differences in event rates (events per 1000 person-years) for 4 outcomes comparing generic and brand L-T4 therapy: (1) atrial fibrillation (1.82 vs 2.19; hazard ratio [HR], 1.22; 95% CI, 0.90-1.65; P=.19); (2) myocardial infarction (2.12 vs 1.83; HR, 0.86; 95% CI, 0.64-1.17; P=.35); (3) congestive heart failure (2.27 vs 2.00; HR, 0.88; 95% CI, 0.66-1.18; P=.41); and (4) stroke (3.10 vs 2.38; HR, 0.77; 95% CI, 0.59-1.00; P=.05). Stratification by age group revealed no differences.

CONCLUSION

In patients with newly treated hypothyroidism, cardiovascular event rates were similar for generic and brand L-T4.

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.