Smoking history and underlying lung disease are associated with poor outcome in patients developing interstitial pneumonia during low-dose amiodarone therapy

BackgroundAmiodarone is a useful antiarrhythmic drug, especially in patients with serious heart diseases, but amiodarone-induced interstitial pneumonia (AMD-IP) is sometimes lethal.Methods and resultsWe retrospectively analyzed the clinical characteristics of 280 patients who were treated with daily oral amiodarone. Among the patients, 29 (10.2%) developed AMD-IP during the follow-up period of 66.0±38.2 months. The average dose of amiodarone in the AMD-IP group (173±10 mg) was significantly higher than that in the non-AMD-IP group (150±3 mg). The prevalence of smoking history (AMD-IP group: 70.0%; non-AMD-IP group: 42.2%; P<0.01) and underlying lung disease (AMD-IP group: 17.2%; non-AMD-IP group: 5.6%; P<0.05) was significantly higher in the AMD-IP group than in the non-AMD-IP group. Furthermore, multiple stepwise logistic regression analysis demonstrated that smoking history was an independent predictor of AMD-IP (OR, 3.56; 95% CI, 1.08–10.23; P<0.001). Among patients who developed AMD-IP, those with chronic obstructive pulmonary disease (COPD) had a higher relapse rate and a worse prognosis.ConclusionsDuring the mean follow-up period of >5 years, 10.2% of patients receiving low-dose amiodarone therapy developed AMD-IP. Higher maintenance doses, smoking history, and preexisting lung disease were related to the development of AMD-IP. The AMD-IP patients with COPD had a poor prognosis.