Incidence Rate of Adverse Drug Reactions During Long-term Follow-up of Patients Newly Treated with Amiodarone

The aim of this observational prospective study was to assess the incidence rate and the characteristics of adverse drug reactions (ADRs) induced by amiodarone during the long-term follow-up of 98 French patients. Inclusions were performed between March 1994 and April 1997. Eligible patients were consecutive outpatients for whom amiodarone was initiated for the first time. The treatment had to be taken for at least 6 months if no ADR required its withdrawal. A cohort of 57 men and 41 women, mean age 72.6 years (SD: 8.6), was followed for a mean period of 38 months. The incidence rate of ADRs during the overall follow-up period was 13.91 cases for 100 person-years. Recorded ADRs were 13 hypothyroidism (incidence rate for 100 person-years: 4.61 [95% confidence interval: 4.58-4.63], 5 hyperthyroidism (1.62 [1.60-1.63]), 10 bradycardia and/or conduction ADRs (3.48 [3.46-3.50]), 7 photosensitivity (2.27 [2.25-2.28]), 1 storage disease (0.33 [0.32-0.33]), 3 interstitial pneumonitis (0.97 [0.96-0.98]), 2 peripheral neuropathies (0.65 [0.64-0.66]), 1 tremor (0.32 [0.32-0.33]) and 1 gastrointestinal disturbances (0.32 [0.32-0.33])). Thyroid and cardiac ADRs occurred mainly during the first 6 months. According to the French system of pharmacovigilance, 27 ADRs were "probable/likely" and 14 were "possible." Hypothyroidism, cardiac ADRs, and photosensitivity were the most frequent ADRs. None of the ADRs had a fatal outcome in this study.