Those findings are reported in the American Journal of Cardiology online by Dr. Louise Pilote, at McGill University, Montreal, Quebec, Canada, and colleagues.
They note that pulmonary toxicity is one of amiodarone’s most serious adverse effects, occurring in 1% to 10% of patients in clinical trials. To clarify the risk in “a real-world atrial fibrillation (AF) population,” the team used linked databases to identify 6460 users and 50,993 nonusers of amiodarone among patients aged 65 and older with AF in Quebec between 1999 and 2007.
Pulmonary toxicity was defined as pulmonary fibrosis, alveolar/interstitial lung disease, or adult respiratory distress syndrome. These conditions occurred in 3.87% of amiodarone users compared with 1.33% of nonusers, the investigators found.
“The nonusers’ pulmonary toxicity incidence rate of 1.33% may partly represent the underlying rate of idiopathic pulmonary fibrosis in the general population and misclassification of nonusers who during follow-up subsequently became amiodarone users,” the authors comment.
The age-standardized incidence of pulmonary toxicity was 28.30 and 16.02 per 1000 person-years in men and women users of amiodarone, respectively, compared with 14.05 and 8.82 per 1,000 person-years among nonusers, respectively, according to the report.
The risk was not dose dependent, with a hazard ratio for pulmonary toxicity of 1.63 for doses up to 200 mg/d and of 1.46 for doses higher than 200 mg/d.
Other risk factors for pulmonary toxicity included increasing age, male gender, COPD, and renal disease, Dr. Pilote and colleagues report.
“Identification of potential risk factors for pulmonary toxicity may assist clinicians in targeting surveillance to those at higher risk,” they suggest. “In patients considered at very high risk of pulmonary toxicity, some clinicians may consider alternative long-term antiarrhythmics, (sotalol, dronedarone), although these agents are less effective than amiodarone.”
Population-Level Incidence and Risk Factors for Pulmonary Toxicity Associated With Amiodarone
Am J Cardiol 2011.