Oral sodium phosphate (OSP) products cleanse the bowels and are commonly used by patients preparing to undergo a colonoscopy (colon examination to detect precancerous growths).  On December 11, 2008, the FDA added a “boxed warning,” commonly referred to as a black box warning, to the label of OSP products to warn of a potential serious side effect, acute phosphate nephropathy.  The OSP products include Visicol and OsmoPrep.  The same day the FDA issued the black box warning mandate, C.B. Fleet recalled an over-the-counter OSP, Fleet Phospho-soda because the FDA determined that OSPs should not be available over-the-counter because of the risk of acute phosphate nephropathy related to OSPs used for bowel cleansing.

What is Acute Phosphate Nephropathy? 

Acute phosphate nephropathy is an acute kidney injury.  It is associated with deposits of calcium-phosphate crystals in the renal tubules that may result in permanent renal function impairment. Acute phosphate nephropathy is rare,  but, it is also a serious adverse side effect that has been associated with the use of OSPs.

OSP & Acute Phosphate Nephropathy Risk Profile

According to the FDA, individuals who appear to have an increased risk of acute phosphate nephropathy following the use of oral sodium phosphates include, individuals who:

  • those of advanced age, over the age of 55
  • are hypovolemic
  • have decreased intravascular volume
  • have baseline kidney disease
  • have a bowel obstruction
  • have active colitis
  • are using medications that affect renal perfusion or function (e.g., diuretics, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and possibly nonsteroidal anti-inflammatory drugs NSAIDs)
  • Individuals at increased risk include:  those of advanced age, those with decreased intravascular volume or kidney disease, and those using medicines that affect renal perfusion or function [diuretics, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and possibly nonsteroidal anti-inflammatory drugs (NSAIDs).

FDA Healthcare Professional Recommendations for Avoiding Acute Phosphate Nephropathy From OSPs

The FDA has advised healthcare professionals that they should consider the following when choosing a bowel cleanser for their patients: 

  • avoid use of OSP in patients with kidney disease, impaired renal function or perfusion, dehydration, or uncorrected electrolyte abnormalities
  • avoid exceeding the recommended OSP doses and avoid concomitant use of laxatives containing sodium phosphate. Use OSP with caution in patients taking diuretics, ACE inhibitors, ARBs, and NSAIDs.
  • encourage patients to take the correct OSP dose and drink sufficient quantities of fluids during bowel cleansing. The FDA has noted that two published articles suggest that using an electrolyte rehydration solution may decrease the electrolyte abnormalities and hypovolemia associated with OSP bowel cleansing
  • Obtain baseline and post-procedure labs (electrolytes, calcium, phosphate, BUN, and creatinine) in patients who may be at increased risk of serious adverse event, including those with vomiting and/or signs of dehydration
  • Use hospitalization and intravenous hydration during bowel cleansing to support frail patients who may be unable to drink an appropriate volume of fluid or may be without assistance at home.

FDA’s December 11, 2008 Actions Regarding OSPs Go Beyond a Boxed Warning

The FDA is concerned about the risk of acute phosphate nephropathy, a type of kidney injury that can be caused by OSP.  OSP laxatives can lead to dehydration and increased levels of phosphate in the kidneys which cause an overproduction of crystals that can damage the organs.

In 2006, the FDA issued a Science Paper outlining the potential risks stemming from OSP products for bowel cleansing.  Since that time, it has received 20 reports of kidney damage from patients who used OsmoPrep.  Of those cases, three were biopsy-proven cases of acute phosphate nephropathy.  The time in which patients became symptomatic varied.  For some, the onset of injury occurred within several hours of ingestion, but in other cases the effects manifested up to 21 days after use.  Patients over the age of 55 and those with pre-existing kidney problems are at special risk. 

In addition to the warning labels, the FDA is requiring the manufacturer of OSP products to take further measures, including the development of a risk evaluation and mitigation strategy (REMS).  Drug makers will also be required to distribute a Medication Guide alerting patients of the potential risk, and to conduct post-marketing clinical trials to better determine the risk associated with OSP use.  The FDA has also issued a recommendation that consumers not use OTC OSP laxatives for bowel cleansing.  Additionally, OSP products should not be used in conjunction with other laxative products containing sodium phosphate or by children under 18 years of age.            

Because OSP products are not intended for long term use, patients that may have used them once may sustain kidney impairment. For instance, if a patient uses Visicol or Fleet Phospho Soda in preparation for certain medical procedures such as a colonoscopy, using the drug just that one time could potentially cause kidney damage. OSPs have even been linked to Fleet Phospho Soda kidney failure and Visicol kidney failure.

If you have suffered an injury – Seek Legal action

If you or a loved one has used an OSP and suffered from acute phosphate nephropathy, or any Visicol side effects or Fleet Phospho Soda side effects, you may be entitled to compensation.  Contact our OSP injury lawyers and attorneys today for a confidential, free, no-obligation case evaluation to see if you have a potential Visicol lawsuit or Fleet Phospho Soda lawsuit.

Published November 17, 2011 by