Hyponatremia - a rare but serious complication of amiodarone: a case report and review of the literature.

Introduction: Hyponatremia secondary to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) during amiodarone therapy is a rare but potentially lethal adverse effect. We report a case of severe hyponatremia associated with amiodarone, and discuss its clinical implications.

Case Report: An 84-year-old Caucasian man with a past medical history of hypertension and diabetes was admitted to the hospital with a non-ST elevation myocardial infarction. He underwent coronary artery bypass graft and developed atrial fibrillation on postoperative day 2. A loading dose of amiodarone followed by a maintenance dose was started. The serum sodium level was 136 mmol/l at discharge and subsequently decreased to 105 mmol/l 11 days later, at which time the patient represented with altered mental status. The diagnosis of SIADH was made based on euvolemic hypoosmotic hyponatremia, lack of any other medication known to cause SIADH and urine that was less than maximally dilute. The serum sodium increased gradually to 123 mmol/l after 36 h of treatment with hypertonic saline, demeclocycline and fluid restriction.

Conclusion: SIADH-induced hyponatremia associated with amiodarone occurs rarely. Since severe hyponatremia is associated with significant neurological damage and mortality, clinicians should carefully monitor serum sodium during amiodarone therapy.