Incidence of thyroid dysfunction rates similar in patients treated with either formulation
TUESDAY, July 12 (HealthDay News) -- The incidence of thyroid dysfunction is similar in patients with atrial fibrillation treated with brand-name or generic formulations of amiodarone, according to a study published online July 11 in CMAJ, the journal of the Canadian Medical Association.
Meytal A. Tsadok, Ph.D., of the McGill University Health Center in Montreal, and colleagues compared the risk of thyroid dysfunction in patients treated with generic amiodarone with those treated with the brand-name formulation. The retrospective cohort study of 60,220 patients with atrial fibrillation, aged 66 years or older, was conducted using demographic information, prescription drug claims, and hospitalizations. Thyroid dysfunction was estimated using person-year incidence.
The investigators found that brand-name and generic formulations were used by 4.7 and 10.4 percent of the patients, respectively. Both groups of patients had similar baseline characteristics and a median maintenance dose of 200 mg/d. Both brand-name and generic amiodarone had a total incidence rate for thyroid dysfunction of 14.1 per 100 person-years. The mean time to clinical thyroid dysfunction was 4.32 and 4.09 years for the brand-name and generic formulations, respectively. After multivariate analysis, no significant difference in the incidence rates between the two formulations was found.
"In this population-based study, we did not detect a difference between the effects of brand and generic formulations of amiodarone on the incidence of thyroid dysfunction," the authors write.
One of the study authors disclosed financial relationships with the pharmaceutical and medical technology industries.