A systematic review 1 included 4 double-blind RCTs with a total of 1 465 subjects. The patients were on a maintenance dose of 400 mg/day (low-dose treatment) for at least 12 months. A higher likelihood of experiencing adverse effects as a result of low-dose amiodarone was found: thyroid OR 4.2 (95% CI 2.0 to 8.7), neurologic OR 2.0 (1.1 to 3.7), skin OR 2.5 (1.1 to 6.2), ocular OR 3.4 (1.2 to 9.6), bradycardic OR 2.2 (1.1 to 4.3). The odds of discontinuing the drug in the amiodarone group were approximately 1.5 times that of the placebo group (OR 1.52, 95% CI 1.2 to 1.9).
According to another review 2, amiodarone appears to be associated with a low incidence of proarrhythmic events with torsade de pointes developing in less than 1% of cases.
Clinical comment: The frequency of most adverse effects is related to the total amiodarone exposure (i.e., dosage and duration of treatment). Therefore, the dosage of amiodarone should be kept at the lowest effective level 3. Laboratory studies to assess liver and thyroid function should be performed regularly. If the patient is also taking digoxin and warfarin, special attention must be paid to digoxin levels and prothrombin time; the effects of interaction with amiodarone do not peak until 7 weeks after the initiation of concomitant therapy.
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