A Case of Laxative-Induced Severe Hypermagnesemia in a Peritoneal Dialysis Patient

A 55-year-old man undergoing peritoneal dialysis (PD) was transferred from a rehabilitation facility to our hospital due to altered consciousness and respiratory distress. Upon arrival, he presented with a Glasgow Coma Scale score of E3V5M6 and hypercapnia with a pCO₂ of 54.6 mmHg. His reduced urine output raised concerns for uremia secondary to diminished residual renal function, prompting the urgent initiation of hemodialysis. However, subsequent investigations revealed that he had been taking magnesium oxide (1980 mg/day) as a laxative and that his serum magnesium level was markedly elevated at 8.4 mg/dL, consistent with hypermagnesemia. Magnesium toxicity, impaired consciousness, and hypercapnia improved after hemodialysis and the cessation of magnesium oxide. The patient was ultimately switched back to PD without recurrence of hypermagnesemia and was discharged. It is important to note that magnesium clearance in patients undergoing PD relies primarily on residual renal function; thus, in patients with diminished residual renal function, the use of magnesium-containing laxatives may precipitate severe hypermagnesemia. Careful consideration is warranted when prescribing magnesium-containing laxatives in patients with diminished residual renal function, even those undergoing PD.