D1.238 - Urgent desensitization to amiodarone

Amiodarone is an antiarrhythmic agent and is often used to treat supraventricular and ventricular arrhythmias.Amiodarone-induced anaphylaxis is rare. The exact cause of anaphylaxis to amiodarone is still unknown. While polysorbate 80 is considered a significant contributing factor, the role of amiodarone itself and its iodide component cannot be fully ruled out. The aim is to analyze the effectiveness of a rapid desensitization protocol to amiodarone.

67-year-old male, diagnosed with hypertrophic cardiomyopathy, left ventricular ejection fraction of 35%, ventricular tachycardia, and implantable cardioverter defibrillator (ICD) under heart transplant code 0.

During an emergency visit for ventricular tachycardia, the patient developed a diffuse urticarial rash following the administration of intravenous amiodarone. The medication was discontinued, and steroids and an antihistamine were administered.

A few months later, he was admitted to the intensive care unit due to arrhythmic storm. Intravenous procainamide treatment was initiated, and ten days after the infusion, he developed palmoplantar pruritus, dyspnea, and a skin rash. Due to concerns about his recent hypersensitivity reaction to procainamide and his history of a reaction to amiodarone, an allergy consultation was requested. Given the urgent need for amiodarone treatment due to the patient's critical condition, the history was considered consistent with an immediate hypersensitivity reaction to amiodarone. A 13-step desensitization (DS) protocol (Figure 1) was developed, which included premedication with dexchlorpheniramine, montelukast, famotidine, and methylprednisolone.

The desensitization protocol was completed in almost 6 hours without any allergic incidents. However, as an adverse event, the patient experienced multiple episodes of ventricular tachycardia with syncope, which responded immediately after ICD activation during the first bag infusion. No further ventricular arrhythmias were observed after the second solution. The target dose (loading dose of amiodarone) set by cardiology was 200 mg, and the amiodarone infusion was continued at 900 mg over 24 hours intravenously.

We present a case of amiodarone desensitization in a patient in a life-threatening condition. Overall, there was a significant risk with readministration of the drug. However, in a patient with this unique clinical context where the benefits of the medical therapy were clear, we were able to use a desensitization protocol to help safely administer amiodarone. After the completion of the protocol, the patient was continued on amiodarone without any complications.