Anti-amiodarone antibodies: Detection and relationship to the development of side effects**

Purpose It has become evident in the past few years that amiodarone, a powerful antiarrhythmic agent, induces considerable side effects. These may be due to an amiodarone-elicited lipid storage disease and to the iodine content of amiodarone, but might also be causally related to amiodarone-induced immune reactions. The latter possibility prompted us to develop a sensitive anti-amiodarone antibody detection assay based on the immunodot technique. Patients and methods Sera were obtained from 10 untreated control subjects and 33 patients receiving amiodarone. Using serum dilutions of 1:500 and 1:1,000, the lower detection limit was 0.3 μg/ml of anti-amiodarone antibodies as calculated from a simultaneously performed IgG standard curve. Results Screening of sera from the untreated control subjects and amiodarone-treated patients revealed that the untreated subjects had no antiamiodarone antibodies, that only one of 16 patients without clinical side effects had elevated anti-amiodarone antibodies, but that seven of 12 patients with amiodarone-induced thyroid disease and four of five patients with other side effects had elevated anti-amiodarone antibody titers (1.2 to 2.5 μg/ml). The combined evaluation of anti-amiodarone antibody titers and cumulative dose was found to be a highly reliable indicator of side effects, as all patients with more than 100-g cumulative dose of amiodarone and more than 0.6 μg/ml of anti-amiodarone antibodies had side effects. Conclusion The detection of anti-amiodarone antibodies in patients with amiodarone-elicited side effects underscores the possible contribution of immunologic reactions to the development of certain side effects.