FDA Requires New Safety Measures for Oral Sodium Phosphate Products to Reduce Risk of Acute Kidney Injury

Risk associated with both prescription and over-the-counter (OTC) products

Today, the U.S. Food and Drug Administration announced that it will add a Boxed Warning to the prescription oral sodium phosphate products Visicol and OsmoPrep to warn consumers about the risk of acute phosphate nephropathy (a type of acute kidney injury). Patients routinely take OSP products to cleanse the bowel before a colonoscopy (colon examination) and other medical procedures.

The FDA has also directed the manufacturer of these products to develop a risk evaluation and mitigation strategy (REMS), distribute a Medication Guide to alert patients to the risk of acute kidney injury associated with the use of these products, and to conduct a postmarketing clinical trial to further assess the risk of acute kidney injury with the use of these products.

The agency is equally concerned about the risks associated with the use of OSP products that are available over-the-counter (OTC), for example, Fleet Phospho-soda, when used at higher doses for bowel cleansing. The available data do not show a risk of acute kidney injury when these OTC products are used at the lower doses for laxative use. However, when used for bowel cleansing, these products have the same risks as prescription OSP products. FDA plans to amend the labeling conditions for OTC OSP products to address this concern with bowel cleansing use. In light of the continued receipt of reports of acute phosphate nephropathy, FDA is recommending that consumers not use over-the-counter OSPs for bowel cleansing.

“Though rare, these are serious adverse events associated with the use of oral sodium phosphates -- both prescription and over-the-counter products,” said Janet Woodcock, M.D., director, FDA’s Center for Drug Evaluation and Research. “In some cases, these serious adverse events occurred in patients with no pre-existing health factors that would have put them at risk for developing kidney injury. We cannot rule out, however, that some of these patients were dehydrated prior to ingestion of OSP products or they did not drink sufficient fluids after ingesting OSP products.”

In 2006, the FDA issued a Science Paper and a Healthcare Professional sheet describing the risks associated with the use of OSP products for bowel cleansing. Since then, as part of the Agency’s postmarketing surveillance, the FDA has received reports of 20 unique cases of kidney injury associated with the use of OsmoPrep. Of the reported cases, three were biopsy-proven cases of acute phosphate nephropathy. The onset of kidney injury in these cases varied, occurring in some within several hours of use of these products and in other cases up to 21 days after use.

OSP products should not be used by children under 18 years of age or in combination with other laxative products containing sodium phosphate. FDA is recommending that OSP prescription products be used with caution for bowel cleansing by the following at risk groups:

• people over 55 years of age,
• people who suffer from dehydration, kidney disease, acute colitis, or delayed bowel emptying, and
• 
  
people taking certain medicines that affect kidney function, such as diuretics (fluid pills), angiotensin converting enzyme inhibitors (medications that lower blood pressure) angiotensin receptor blockers, (used to treat high blood pressure, heart or kidney failure) and possibly nonsteroidal anti-inflammatory drugs (similar to ibuprofen and other arthritis medications).

Health care professionals and consumers may report serious adverse events (side effects) or product quality problems with the use of these products to the FDA's MedWatch Adverse Event Reporting program either online, by regular mail, fax or phone.

--Online: www.fda.gov/MedWatch/report.htm
--Regular Mail: use postage-paid FDA form 3500 available at: www.fda.gov/MedWatch/getforms.htm
and mail to:
MedWatch, 5600 Fishers Lane, Rockville, MD 20852-9787
--Fax: (800) FDA-0178
--Phone: (800) FDA-1088

Safety Alert: Oral Sodium Phosphate (OSP) Products for Bowel Cleansing
http://www.fda.gov/cder/drug/infopage/OSP_solution/default.htm

Oral Sodium Phosphate (OSP) Products for Bowel Cleansing
(marketed as Visicol and OsmoPrep, and oral sodium phosphate products available without a prescription)

FDA has become aware of reports of acute phosphate nephropathy, a type of acute kidney injury, associated with the use of oral sodium phosphate products (OSP) for bowel cleansing prior to colonoscopy or other procedures. These products include the prescription products, Visicol and OsmoPrep, and OSPs available over-the-counter without a prescription as laxatives (e.g., Fleet Phospho-soda). In some cases when used for bowel cleansing, these serious adverse events have occurred in patients without identifiable factors that would put them at risk for developing acute kidney injury. We cannot rule out, however, that some of these patients were dehydrated prior to ingestion of OSPs or they did not drink sufficient fluids after ingesting OSP.

Acute phosphate nephropathy is a form of acute kidney injury that is associated with deposits of calcium-phosphate crystals in the renal tubules that may result in permanent renal function impairment. Acute phosphate nephropathy is a rare, serious adverse event that has been associated with the use of OSPs. The occurrence of these events was previously described in an Information for Healthcare Professionals sheet and an FDA Science Paper issued in May 2006. Additional cases of acute phosphate nephropathy have been reported to FDA and described in the literature since these were issued.

Individuals who appear to have an increased risk of acute phosphate nephropathy following the use of OSPs include persons: who are over age 55; who are hypovolemic or have decreased intravascular volume; who have baseline kidney disease, bowel obstruction, or active colitis; and who are using medications that affect renal perfusion or function (such as diuretics, angiotensin converting enzyme [ACE] inhibitors, angiotensin receptor blockers [ARBs], and possibly nonsteroidal anti-inflammatory drugs [NSAIDs]).

As a result of new safety information received, FDA is requiring the manufacturer of Visicol and OsmoPrep, the two OSPs available by prescription only, to add a Boxed Warning to the labeling for these products. FDA is also requiring that the manufacturer develop and implement a risk evaluation and mitigation strategy (REMS), which will include a Medication Guide, to ensure that the benefits of these products outweigh the risk of acute phosphate nephropathy, and to conduct a postmarketing clinical trial to further assess the risk of acute kidney injury with use of these products.

FDA acknowledges that OSP products, in addition to use for bowel preparation, have a long history of safe use as non-prescription products as laxatives (i.e. for relief of constipation) and accordingly, they will continue to be available over-the-counter for this use. However, in light of the risk of acute phosphate nephropathy, over-the-counter laxative OSP products should not be used for bowel cleansing. Consumers should only use OSPs for bowel cleansing pursuant to a prescription from a healthcare professional. FDA intends to amend the labeling conditions for OSP products available in the OTC setting to address this concern with bowel cleansing use and to improve the safe use of OSPs that are available over-the counter. FDA’s amendment to remove the professional labeling for bowel cleansing for these OSPs available over-the-counter will be published in a future Federal Register notice.