The administration of magnesium is an effective therapeutic option in such conditions as preeclampsia, ischemic heart disease, cardiac arrhythmia, and asthma. It has also been used as a cathartic in the treatment of constipation. As a medical therapy, magnesium enjoys an acceptable safety record. Because magnesium is almost exclusively excreted in the urine, significantly elevated levels of magnesium are typically anticipated only in patients with renal dysfunction. With wider application, emerging reports suggest that additional factors such as intestinal hypomotility and chronic constipation should be considered before using magnesium to avoid toxicity.