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Oral Sodium Phosphate Safety Alerts

Patients with chronic kidney disease (CKD) who use bowel cleansing products should be aware of a recent warning issued by the FDA for a type of sudden loss of kidney function or acute kidney injury, as well as, blood mineral disturbances. Phosphate crystal deposition in the kidneys causes the loss of kidney function, which can lead to kidney failure. The medical term for this condition is acute phosphate nephropathy.

The warning relates to the use of bowel cleansing agents, called sodium phosphate (OSP) products as laxatives or in preparation for colonoscopy. OSPs are available both with and without a prescription and are taken by mouth. These products can cause phosphate nephropathy.

Oral sodium phosphates clear the bowel by making bowel movements frequent, loose and runny. These agents work by causing fluid loss so it is recommended to patients that they drink large quantities of clear liquids as part of the bowel preparation.

Symptoms of acute phosphate nephropathy are:

  • Lethargy
  • Drowsiness
  • Decreased urination
  • Swelling of ankles, feet and legs

Early on, people may not have any symptoms at all. Anyone at high risk for this condition should have their kidney function monitored by their doctor.

Visicol® and OsmoPrep® are available by prescription only. Other similar OSP products are non-prescription, and can be used as a laxative at low doses.

Children under 18 years should not use these products alone or in combination with other laxatives containing sodium phosphate. Others groups who are at risk for acute phosphate nephropathy are:

  • People over 55
  • CKD patients
  • People who are dehydrated
  • People who have bowel obstruction, delayed bowel emptying or active colitis
  • People taking medications such as diuretics, angiotensin converting enzyme [ACE] inhibitors, angiotensin receptor blockers [ARBs], and inflammation and pain relief medications such as nonsteroidal anti-inflammatory drugs [NSAIDs]

The FDA requested that the manufacturer of Visicol® and OsmoPrep®, Salix Pharmaceuticals;

  • Add a black boxed warning to the pharmacy package insert for these products
  • Develop and distribute a medication guide for patients that is easier for most patients to understand than package inserts
  • Arrange a post-marketing trial to assess the risks to patients taking OSP products

Non-prescription OSP products have a long history of safety when used as laxatives and will still be available over the counter. However, because of the recent warning by the FDA, those OSP products should only be used as laxatives and not for bowel cleansing. The FDA suggests consumers should get a prescription from a health care professional when thinking about having a bowel cleansing.

The U.S. Preventive Services Task Force (USPSTF) strongly recommends that clinicians screen men and women 50 years of age or older for colorectal cancer with one of several tests, including colonoscopy. If your doctor recommends colonoscopy, concerns about bowel cleansing should not prevent you from undergoing colon cancer screening. Colon cancer is treatable when the disease is caught early and the best treatment is to identify and remove precancerous polyps before they progress to cancer.

A high-quality and safe colon cleansing preparation is important for colon cancer screening using colonoscopy. There are other FDA-approved alternatives to OSP for bowel preparation prior to colonoscopy that may be safer for some patients, but may not always clean the bowel adequately. Patients should discuss the risks of the preparation and procedure, versus the benefits of the screening to determine the best bowel cleaning agent for their age, and risk conditions noted above.

More than 37 million American adults and thousands of American children have Chronic Kidney Disease. Most do not know they have this condition.

Date Reviewed: July 2009

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© 2015 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.

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