THURSDAY, Jan. 9, 2014 (HealthDay News) — If you are constipated and need to use a laxative, the U.S. Food and Drug Administration wants you to know that some products can be dangerous if you don’t follow the dosing instructions or you have certain medical conditions.

The agency said there have been dozens of reports of serious side effects, including 13 deaths, among people taking sodium phosphate laxatives, which are sold over-the-counter.

Laxatives with sodium phosphates are marketed under the brand name “Fleet” and also as store brands and generic products. All of them can cause serious side effects if used improperly. These side effects include dehydration or abnormal levels of electrolytes in the blood that can lead to complications such as kidney damage and death.

The labels on these products state that they should be used as a single dose taken once a day, should not be used for more than three days, and that patients who are dehydrated or have kidney disease or heart problems should consult a health care professional before taking these laxatives.

The FDA also said that adults older than 55 and children with certain health conditions should talk to a health care professional before using sodium phosphate laxatives because they may be at increased risk for harmful side effects.

The new warnings, which are not currently included on the label on these laxatives, apply to adults and children with inflammation of the colon and those taking certain drugs, including: medicines that affect how the kidneys work, such as diuretics or fluid medicines; blood pressure drugs such as angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs); heart or kidney failure medications; and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.

“The bottom line is that these products are safe for otherwise healthy adults and older children . . . as long as they follow these dosing instructions and don’t take the product more often, or in greater amounts, than the label instructs,” Dr. Mona Khurana, a medical officer in FDA’s division of nonprescription regulation development, said in an agency news release.

In recent reviews, the FDA has identified 54 cases of serious side effects associated with the oral or rectal use of sodium phosphate laxatives in adults and children. Twelve adults and one child died.

More information

The American Academy of Family Physicians has more about laxatives.