Concurrent Use of Thyroid Hormone Therapy and Interfering Medications in Older US Veterans.

CONTEXT: Thyroid hormone management in older adults is complicated by comorbidities and polypharmacy. OBJECTIVE: Determine the prevalence of concurrent use of thyroid hormone and medications that can interfere with thyroid hormone metabolism (amiodarone, prednisone, prednisolone, carbamazepine, phenytoin, phenobarbital, tamoxifen), and patient characteristics associated with this practice. DESIGN: Retrospective cohort study between 2004 and 2017 (median follow-up, 56 months). SETTING: Veterans Health Administration Corporate Data Warehouse. PARTICIPANTS: A total of 538 137 adults ≥ 65 years prescribed thyroid hormone therapy during the study period. MAIN OUTCOME MEASURE: Concurrent use of thyroid hormone and medications interfering with thyroid hormone metabolism. RESULTS: Overall, 168 878 (31.4%) patients were on at least 1 interfering medication while on thyroid hormone during the study period. In multivariable analyses, Black/African-American race (odds ratio [OR], 1.25; 95% CI, 1.21-1.28, compared with White), Hispanic ethnicity (OR, 1.12; 95% CI, 1.09-1.15, compared with non-Hispanic), female (OR, 1.11; 95% CI, 1.08-1.15, compared with male), and presence of comorbidities (eg, Charlson/Deyo Comorbidity Score ≥ 2; OR, 2.50; 95% CI, 2.45-2.54, compared with 0) were more likely to be associated with concurrent use of thyroid hormone and interfering medications. Older age (eg, ≥ 85 years; OR, 0.48; 95% CI, 0.47-0.48, compared with age 65-74 years) was less likely to be associated with this practice. CONCLUSIONS AND RELEVANCE: Almost one-third of older adults on thyroid hormone were on medications known to interfere with thyroid hormone metabolism. Our findings highlight the complexity of thyroid hormone management in older adults, especially in women and minorities.