Which patient is at greatest risk for developing hypermagnesemia?

• A. 42-year-old woman with systemic lupus erythematosus and renal failure
• B. 83-year-old man with lung cancer and hypertension
• C. 65-year-old woman with hypertension taking beta-blockers
• D. 50-year-old man with benign prostatic hyperplasia and a urinary tract infection

Answer: (A)

Magnesium is cleared by the kidneys, so when kidney function is impaired, magnesium can accumulate in the body. In systemic lupus erythematosus with renal involvement, the kidneys’ filtering ability is often reduced, increasing the risk of hypermagnesemia, especially if magnesium-containing medications or supplements are used. The other scenarios don’t involve significant renal dysfunction, so their risk of elevated magnesium is much lower. Hence, the patient with lupus who has renal failure is at greatest risk.