Do not use a laxative containing sodium phosphate, unless recommended by your health care provider.
Such oral or rectal products, sometimes called saline laxatives (the best known brand is Fleet), are mostly used to prepare for certain bowel procedures, not for constipation. They draw water into the large intestine, which softens the stool and makes it easier to pass.
But, as the Food and Drug Administration (FDA) recently warned, they have been linked to kidney damage and other complications, including 13 deaths, resulting from dehydration and/or electrolyte imbalance in the blood. People taking drugs that affect kidney function, such as diuretics, ACE inhibitors, and some other blood pressure drugs, as well as nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, are at increased risk for adverse effects.