Background: Amiodarone is a class III antiarrhythmic agent used for the management of certain cardiac arrhythmias. Although effective and relatively safe, amiodarone is associated with a spectrum of adverse effects including neurotoxicity. There have been sparse reports of drug-induced parkinsonism (DIP) as a consequence of amiodarone use; however, the mechanism and clinical implications remain an area of limited understanding and documentation. Parksinon’s disease (PD) is associated with degeneration of dopaminergic pathways in the basal ganglia, manifesting in the classic constellation of symptoms, including “pill-rolling” tremors. These dopaminergic pathways can also be disrupted by certain medications, notably antipsychotics, antiemetics, and antiepileptics, which may mimic the symptoms of PD.

Case Presentation: 92 year-old female with a past medical history of atrial fibrillation, hypothyroidism, heart failure, COPD, and dementia presented with resting tremors of the bilateral hands for 2 months. Pt endorsed no new bradykinesia, loss of balance, or muscle stiffness. Denied any fever, chills, myalgia, cough, dysuria, nausea, vomiting, diarrhea, or weight gain or loss. Physical exam demonstrated isolated bilateral resting tremors, with an otherwise unremarkable neurologic exam. There was no muscle rigidity, cerebellar dysfunction, motor/sensory deficits, or bradykinesia compared to baseline. Vital signs were normal and labwork including TSH, RPR, and vitamins B12 and B9 were unremarkable. Following review of the patient’s medication regimen, we reduced amiodarone dosing from 200mg to 100mg due to concern for neurotoxicity rather than late-onset PD. On follow up at 2 weeks and 1 month, resting tremors resolved completely and the patient had no further concerns.

Discussion: Despite the established neurotoxicity of amiodarone, reports of amiodarone-induced Parkinsonism remain sparse. Here, we present a case of Parkinsonism occurring in a patient receiving long-term amiodarone therapy. Through this case report, we aim to broaden understanding of potential neurotoxic effects of amiodarone and emphasize the importance of recognizing drug-induced parkinsonism (DIP). DIP is a reversible form of Parkinsonism caused by the blockade of dopamine receptors or interference with dopamine transmission in the basal ganglia, mimicking the dopaminergic deficiency seen in PD. Misdiagnosing DIP as Parkinson's disease could lead to inappropriate treatment, potentially causing harm. Hence, clinical vigilance is warranted in patients receiving long-term therapy with amiodarone.