Effect of three laxatives and a cation exchange resin on fecal sodium and potassium excretion

The treatment of hyperkalemia in patients with renal insufficiency often includes the ingestion of sorbitol and a cation exchange resin. Sorbitol alone may be used to remove sodium and water from overloaded patients. The efficacy of these regimens has never been compared with other laxative or laxative-resin combinations. The aim of the study was to compare the relative effect of three laxatives with different mechanisms of action, alone and in combination with resin, on fecal sodium and potassium excretion.

Sodium, potassium, and water excretion in 12-hour stool collections were analyzed after various laxative-resin combinations in normal subjects.

Correctol (yellow phenolphthalein) (Schering Plough Health Care Products, Memphis, TN) was more effective than sorbitol or sodium sulfate in causing fecal sodium and potassium loss. Resin recovery in stool was much greater with phenolphthalein than with other laxatives, and more potassium was excreted in stool with phenolphthalein-resin than with phenolphthalein alone or other laxative-resin combinations. Sorbitol caused more undesirable gastrointestinal symptoms than did sodium sulfate or phenolphthalein.

In normal people, phenolphthalein (1) is preferable to other laxatives in causing fecal sodium and potassium excretion, (2) hastens resin transit through the intestine compared with other laxatives, and (3) produces greater fecal potassium excretion when combined with resin than phenolphthalein alone or other laxative-resin combinations.