Dec. 11, 2008 -- The FDA today ordered a "black box" warning, the FDA's sternest warning, for the prescription oral sodium phosphate products Visicol and OsmoPrep, which are used to cleanse the bowel before a colonoscopy and other medical procedures.
The warning pertains to the risk of acute phosphate nephropathy, which is a type of acute kidney injury.
The FDA also recommends that consumers not use over-the-counter oral sodium phosphate products, such as Fleet Phospho-soda, for bowel cleansing.
According to the FDA, over-the-counter oral sodium phosphate products, when used for bowel cleansing, pose the same kidney risk as the prescription oral sodium phosphate products. But that risk doesn't apply to those over-the-counter products used as laxatives.
Kidney Injury Reports
The FDA has received 20 reports of kidney injury associated with OsmoPrep since OsmoPrep's approval in 2006. Three of those cases were confirmed by biopsy. Some cases happened within hours of use; others were reported days or weeks later.
The FDA has also received reports of 19 cases of acute renal (kidney) failure, seven of which were confirmed by biopsy.
Korvik notes that one reason for the risk might be that some people may be dehydrated and not drinking enough fluid when they use oral sodium phosphate products for bowel cleansing, despite the instructions on the products.
"We don't believe that all of the patients are at risk," Korvik said at a news conference.
Charles Ganley, MD, who directs the FDA's Office of Nonprescription Products, agrees, noting that "the majority" of patients who use those products "don't run into problems."
The FDA has asked Salix Pharmaceuticals, which makes Visicol and OsmoPrep, to do a study to learn more about the kidney risk and how to manage it.
Spokespeople for Salix Pharmaceuticals and for C.B. Fleet Company, which makes Fleet Phospho-soda, were not immediately available for comment.
No Reason to Postpone Colonoscopy
Patients 18 and older can still use Visicol and OsmoPrep for bowel cleansing before colonoscopy or other procedures.
But the FDA recommends that people use caution with those products if they are in the following risk groups:
- People older than 55
- People with dehydration, kidney disease, acute colitis, or delayed bowel emptying
- People taking certain medicines that affect kidney function, such as diuretics, ACE inhibitors, angiotensin receptor blockers, and possibly nonsteroidal anti-inflammatory drugs (NSAIDs).