On November 11, 2008 the Food and Drug Commission issued an alert about the safe use of bowel cleansing products that contain oral sodium phosphate. The FDA is requiring that the manufacturers of prescription Visicol® and OsmoPrep® put Black Box warnings on the labels for these products. In addition, the FDA intends to change labeling for over-the-counter oral sodium phosphate bowel preps including Fleet Phospho-Soda.
New FDA labeling for over-the-counter sodium phosphate products will say that they should not be used for bowel cleansing and will address their safe use as laxatives.
The alert follows more than 20 reports of acute phosphate nephropathy, a kidney injury that can cause permanent kidney damage, after the use of OsmoPrep.
Visicol, OsmoPrep and over-the-counter Fleet Phospho-soda are frequently used to clean the bowels in preparation for colonoscopy or other procedures.
The FDA cannot rule out that some patients who developed kidney injury using oral sodium phosphate were not dehydrated before they began their bowel cleansing or that they did not drink sufficient fluids with the prep.
The manufacturers of Visicol and OsmoPrep are required by the FDA to develop a risk evaluation and mitigation strategy (REMS) that will include a Medication Guide for consumers to help them evaluate the risk and benefits of using the products. In addition, manufacturers must conduct a randomized postmarketing clinical trial to further assess the risk of acute kidney injury, comparing the risk of kidney injury for bowel cleansing with Visicol and OsmoPrep to cleansing with polyethylene glycol (PEG) solutions.
People particularly at risk for acute kidney injury from oral sodium phosphate include patients who:
- are aged 55 and above
- are dehydrated
- have delayed bowel emptying such as with bowel obstruction
- have colitis
- already have kidney disease
- are taking drugs that affect kidney function such as diuretics, ACE inhibitors, angiotensin receptor blockers [ARBs], and possibly nonsteroidal anti-inflammatory drugs
In addition, it is critical that patients be instructed to drink enough water and other fluids during a bowel prep with oral sodium phosphate.
The new Boxed Warning reads:
There have been rare, but serious reports of acute phosphate nephropathy in patients who received oral sodium phosphate products for colon cleansing prior to colonoscopy. Some cases have resulted in permanent impairment of renal function and some patients required long-term dialysis. While some cases have occurred in patients without identifiable risk factors, patients at increased risk of acute phosphate nephropathy may include those with age 55 years and above, hypovolemia, increased bowel transit time (such as bowel obstruction), active colitis, or baseline kidney disease, and those using medicines 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]).
The FDA first alerted consumers and health care professionals of the potential dangers of using oral sodium phosphate preparations in 2006 when they first became aware of cases of acute phosphate nephropathy. Since that time there have been additional kidney damage reports to the FDA, including the reports with OsmoPrep, and more cases reported in medical literature.
Symptoms of acute phosphate nephropathy include feeling ill, drowsiness, lethargy, decreased urine, or swelling of your ankles, feet and legs. Early stages may not be associated with symptoms, and may only be detected by blood tests to measure kidney function (serum creatinine and blood urea nitrogen). It is important to have your doctor follow your kidney function closely, especially if you are at increased risk.
For more information, the FDA has prepared Questions and Answers on the oral sodium phosphate action.