Hyperphosphatemia associated with phosphorus-containing laxatives in a patient with chronic renal insufficiency.

A patient with chronic renal insufficiency had hyperphosphatemia, hypocalcemia, hypomagnesemia, hypokalemia, metabolic acidosis, and QT prolongation on electrocardiogram after taking prescribed laxatives containing phosphorus. Clinical findings included tetany in the form of Chvostek's and Trousseau's signs. Symptoms resolved after careful rehydration and electrolyte replacement. The interactions between these electrolytes are described. Patients with moderate to severe renal dysfunction should avoid use of laxatives containing phosphorus. If these laxatives are used in patients with mild renal dysfunction, careful monitoring is indicated.