Agency cites potential kidney dangers associated with the use of oral sodium phosphate compounds.

The FDA is recommending that only prescription oral sodium phosphate (OSP) bowel preparations be used by patients for bowel cleansing prior to undergoing colonoscopy. The agency also is requiring “black box” warnings on these products.

Following the FDA’s action, C.B. Fleet announced a voluntary recall of its OTC bowel preps, Fleet Phospho-soda and Fleet Phospho-soda EZ-Prep.

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A nephrologist who recently wrote a review paper on the renal risks of pre-colonoscopy bowel preparation welcomes the voluntary withdrawal. “I agree with the FDA warning and think that the Fleet voluntary recall is wise,” said Y. Howard Lien, MD, PhD, whose article was published in Nature Clinical Practice – Nephrology (2008;4:606-614). He is an emeritus professor of medicine at the University of Arizona Health Sciences Center, Tucson.

“The problem with sodium phosphate-based preparations is that the phosphate load is too much for the kidney to handle. Since phosphate can cause multiple renal and electrolyte problems, I would recommend polyethylene glycol-based bowel-cleansing products while waiting for a better preparation.”

The FDA statement noted concern about the risk of acute phosphate nephropathy associated with OSP. The agency is concerned with the risks of OTC Fleet Phospho-soda when used for bowel cleansing, and iIt said that black box warnings are now required for two prescription products made by Salix Pharmaceuticals–Visicol and OsmoPrep.  

Reports of acute phosphate nephropathy from bowel cleansing date back to 2004. Between 2006 and late 2008, the FDA received information about an additional 20 cases of this condition associated with the use of OsmoPrep.

A December 11, 2008, C.B. Fleet statement noted that “since Fleet’s Phospho-soda products are currently labeled and sold as over-the-counter products, Fleet decided to voluntarily remove them from the market as expeditiously as possible to address the FDA’s decision that the products be available by prescription only.”

The FDA asked Salix to develop a risk evaluation and mitigation strategy and to conduct post-marketing trials to assess the risk of this rare but very serious adverse event.