Hypokalemia and metabolic alkalosis resulting from overuse of magnesium oxide.

A 23 year old woman had taken large doses of magnesium oxide (up to 20 to 30g per day) initially for habitual constipation and later for idiopathic edema instead of diuretics, until the concealed abuse was discovered. During the abuse she showed hypokalemia and metabolic alkalosis. When the ingestion was stopped, the electrolyte imbalance recovered within two weeks.