On December 11, 2008, the Food and Drug Administration (FDA) issued a “black box warning” to consumers and health care professionals that a rare but serious form of kidney failure, acute phosphate nephropathy, had been associated with the use of prescription oral sodium phosphate (OSP) products Visicol and Osmo Prep, both made by Salix Pharmaceuticals. The products are routinely prescribed for bowel cleansing prior to colonoscopy, radiographic procedures and surgery. Acute phosphate nephropathy is a rare but serious adverse event that is often permanent and may require chronic dialysis.
The FDA expressed equal concern about the risks associated with over-the-counter (OTC) bowel clearing products such as Fleet Phospho-soda and Fleet Accu-Prep solutions. While the data does not indicate a risk when taking the OTC solutions in lower does for laxative use, when used at higher doses for bowel cleansing, the products carry the same risks as prescription OSP products. 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.
Individuals who appear at increased risk for acute phosphate nephropathy include those older than 55 years of age; people who suffer from dehydration, acute colitis or delayed bowel emptying; and people taking certain medications that affect kidney function, such as diuretics, medicines that lower blood pressure or treat heart or kidney failure and possibly nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and other arthritis medications.
The first case of OSP-related acute phosphate nephropathy was identified in September 2003. Within the next nine months, five more cases related to use of OSP had been reported and were included in the November 2005 publication Human Pathology. On May 5, 2006, the FDA identified OSP bowel cleansing agents as a cause of acute phosphate nephropathy and warned healthcare providers about the higher risk patients and the need for adequate hydration. The FDA issued its sternest warning about OSP products in December 2008.
As a result of the December 2008 FDA Alert, C.B. Fleet Company, Inc., manufacturer of several over-the-counter OSP solutions, voluntarily recalled its OTC products, resulting in the product only being available by prescription. On February 13, 2009, C.B. Fleet ceased the sale of its Fleet Prep Kit 1 product.