We present the case of a patient in whom hypotension, sudden cardiopulmonary arrest, and coma developed after a massive dose of a seemingly harmless cathartic agent. The diagnosis of hypermagnesemia was made 9 hours after the patient's admission, when the serum magnesium concentration was 21.7 mg/dL (8.9 mmol/L). The patient's condition improved with IV calcium, saline solution infusion, and cardiorespiratory support. The elimination half-life of magnesium in this case was 27.7 hours. Few cases have been reported in which patients have survived with serum levels greater than 18 mg/dL (7.4 mmol/L). This case provides evidence that hypermagnesemia may occur in patients with normal kidney function. The diagnosis of hypermagnesemia should be considered in patients who present with symptoms of hyporeflexia, lethargy, refractory hypotension, shock, prolonged QT interval, respiratory depression, or cardiac arrest.

[Qureshi TI, Melonakos TK: Acute hypermagnesemia after laxative use. Ann Emerg Med November 1996;28:552-555.]