In December, we reported that the U.S. Food and Drug Administration (FDA) had ordered the makers of Visicol and OsmoPrep to include black box warnings on the drugs’ labels regarding acute kidney risks associated with prescription sodium phosphate medications (OSPs) that many people take as a bowel prep before colonoscopy. A recent article in Public Citizen’s “Worst Pills, Best Pills” newsletter pointed out that the FDA has received more reports of patients falling ill with acute phosphate nephropathy, a type of serious, acute kidney damage, associated with the use of OSPs.
The FDA said it had seen similar kidney problems in people who used over-the-counter (OTC) sodium phosphate products as bowel preps, and recommended they not be used for this purpose. The FDA said it planned to amend the labeling conditions for OTC OSP products to address this concern with bowel cleansing use. As a result, C.B. Fleet Co. announced a voluntary recall of OTC Fleet Phospho-soda products. The product is a non-prescription laxative, but is often used in larger doses for bowel cleansing.
In 2006, the FDA issued a Science Paper and a Healthcare Professional sheet describing the risks associated with the use of OSPs for bowel cleansing. Since, as part of the agency’s post-marketing surveillance, the FDA has received reports of 20 unique cases of kidney injury associated with the use of OsmoPrep; three were biopsy-proven cases of acute phosphate nephropathy. The FDA said 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.
The FDA also warned that OSPs should not be used by children under 18 years of age or in combination with other laxative products containing sodium phosphate and also recommended that prescription OSPs be used with caution for bowel cleansing by 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 and heart or kidney failure), and, possibly, nonsteroidal anti-inflammatory drugs (similar to ibuprofen and other arthritis medication
Public Citizen noted that acute phosphate nephropathy is a rare, but serious condition in which deposits of calcium-phosphate crystals are trapped in the renal (kidney) tubules and which may result in permanent kidney function impairment. There are safer, equally effective, alternatives to OSPs for pre-colonoscopy bowel cleansing which do not contain sodium phosphate, said Public Citizen. Two of the most commonly used products are Colyte and TriLyte, both oral solutions, which require a presecription, it recommended
The FDA is requiring, reported Public Citizen, the maker of Visicol and OsmoPrep to conduct a post-marketing clinical trial to further assess the risk of acute kidney injury with use of these medications and must also develop and implement a risk evaluation and mitigation strategy (REMS) that is to include a Medication Guide informing patients about the products about benefits and risks of these products.