EurekAlert! -- Magnesium-containing cathartics are commonly used to treat chronic constipation. Although hypermagnesemia is a rare clinical condition, it can occur as a side effect of increased intake of magnesium salts. The Japanese government has recently reported fatal cases of hypermagnesemia in adults treated with magnesium oxide. It is now important for pediatricians to know whether hypermagnesemia can develop in children with functional constipation who are receiving daily magnesium oxide treatment.