THURSDAY, June 27, 2019 (HealthDay News) — Cardiovascular event rates are similar for patients with newly treated hypothyroidism receiving generic and brand levothyroxine (L-T4), according to a study published online April 26 in the Mayo Clinic Proceedings.

Robert C. Smallridge, M.D., from the Mayo Clinic in Jacksonville, Florida, and colleagues conducted a retrospective analysis to examine whether L-T4 preparation (generic versus brand) affected hospitalization for cardiovascular events. A total of 87,902 propensity score-matched patients initiating generic or brand L-T4 (43,951 patients per cohort) were included; patients were followed for a mean of one year.

The researchers found no differences in event rates between patients on generic and brand L-T4 therapy for four outcomes: atrial fibrillation (1.82 versus 2.19 per 1,000 person-years; hazard ratio [HR], 1.22 [95 percent confidence interval, 0.9 to 1.65]; P = 0.19), myocardial infarction (2.12 versus 1.83 per 1,000 person-years; HR, 0.86 [95 percent confidence interval, 0.64 to 1.17]; P = 0.35), congestive heart failure (2.27 versus 2 per 1,000 person-years; HR, 0.88 [95 percent confidence interval, 0.66 to 1.18]; P = 0.41), and stroke (3.1 versus 2.38 per 1,000 person-years; HR, 0.77 [95 percent confidence interval, 0.59 to 1]; P = 0.05). There were no differences after stratification by age group.

“If these observations are confirmed with longer-term follow-up, then either generic or brand L-T4 preparations may be used to treat hypothyroidism due to benign thyroid disorders, at least with respect to the risk of cardiovascular events,” the authors write.

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