If you had a colonoscopy before December 2008 you may remember an over-the-counter Fleet® Phospho-soda® (sodium phosphate) preparation to cleanse your bowels.  This type of product has been around for decades.  It was the favored bowel preparation because it was easy to use, was only a small amount to drink and generally produced a clean colon.  Although sodium phosphate products were thought to be safe, their use was often avoided in patients with known kidney disease, diabetes, elderly patients and patients taking certain blood pressure medications, due to potential concern for kidney impairment in at-risk patients.  At-risk patients were generally given a polyethylene glycol (PEG) based prep which does not impact the kidney, but had the down-side of needing to drink 2-4 liters of the product.

In the past few years, there have been some reports of a specific type of kidney injury from sodium phosphate products called “phosphate nephropathy.”  While the reports of this kidney injury were quite rare, the condition could be severe, ranging from minor impairment to kidney failure.  Although there does appear to be a link between sodium phosphate and kidney injury in published reports, conflicting findings in the medical literature leave us with questions about who is at risk and just how significant is the risk.

In response to new safety concerns, the Food and Drug Administration (FDA) issued an alert in December 2008 and required that sodium phosphate products carry a “black box warning” about phosphate nephropathy.  The FDA advised that over-the-counter sodium phosphate products should not be used for bowel preparation.  The C.B. Fleet Company then voluntarily removed their over-the-counter product from the market.  The FDA warning also applies to prescription, pill-based preparations such as OsmoPrep® and Visicol®.

Most colonoscopies are done for screening and prevention of colon cancer.  Colon cancer can be prevented by finding and removing colon polyps, the precursor to colon cancer.  It makes sense that polyps are most efficiently found and removed when the colon is perfectly clean.  Thus, a good bowel preparation is crucial for the success of the procedure.  An ideal prep is safe, tolerable (low volume and tastes good), effective and inexpensive.  We have now moved to using a non-prescription, PEG-based preparation called MiraLAX®, which we feel meets these criteria.  You will find the directions for the MiraLAX® prep on our website.

Reference:
Corken Mackey A et al.  Sodium phosphate tablets and acute phosphate nephropathy. Am J Gatroenterol 2009;104; 1903-1906.
Russmann S et al.  Risk of further decline in renal function after the use of oral sodium phosphate or polyethylene glycol in patients with a preexisting glomerular filtration rate below 60ml/min. Am J Gastrooenterol 2008;103:2707-16.