100501 - Amiodarone allergy

Amiodarone is a class III antiarrhythmic drug widely used for the treatment of ventricular and supraventricular arrhythmias. Despite its well-known adverse effect profile, immediate hypersensitivity reactions to amiodarone are extremely rare. Only a few cases of suspected immediate hypersensitivity reactions have been reported, and most of them are poorly documented, with limited allergological work-up. To date, no standardized diagnostic approach or clear data regarding cross-reactivity with other antiarrhythmic agents have been established.

A 60-year-old patient with a history of paroxysmal atrial fibrillation since 2017, episodes of atrial flutter, and hypertensive heart disease.

One year prior to evaluation, immediately after the administration of amiodarone, the patient developed hypotension, lower limb pain, and facial angioedema, without cutaneous lesions or other associated symptoms. The patient attended the emergency department, where intravenous methylprednisolone and corticosteroids were administered, with complete resolution of symptoms within 30 minutes. Serum tryptase was not measured during the reaction.

The patient tolerates metoprolol.

Skin testing with amiodarone, procainamide, flecainide, and diltiazem was performed. Intradermal testing with amiodarone (1/10 dilution) was positive, while all other drugs tested negative. Skin tests in healthy controls were negative.

Amiodarone is an iodinated benzofuran derivative. Its antiarrhythmic activity involves potassium channel blockade (class III), sodium channel blockade (class I), calcium channel blockade (class IV), and additional beta-blocking effects (class II). Nevertheless, according to the Vaughan–Williams classification, it is generally considered a class III antiarrhythmic. Its clinical use has expanded over time and includes the management of arrhythmias in various settings, such as outpatient care, prehospital care, atrial fibrillation, advanced cardiac life support, and post–cardiac surgery.

We present a case of amiodarone-induced anaphylaxis with good tolerance to other antiarrhythmic drugs. This case highlights the importance of performing a comprehensive allergological evaluation, including alternative antiarrhythmics, as there is currently no available literature addressing cross-reactivity among these drugs.