Extreme hypermagnesemia caused by an overdose of magnesium-containing cathartics.

We describe a patient who survived a peak serum magnesium level of 9.5 mmol/L (23.0 mg/dL) after an oral cathartic overdose. The patient presented in coma but regained full consciousness over the next six hours with supportive therapy. His serum magnesium had returned to near-normal levels by the following morning at the time of his hospital discharge. This case represents an unprecedented extent of ingestion-related hypermagnesemia in a surviving patient, given that serum levels of more than 8 mmol/L are frequently associated with death from cardiac arrest.