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U.S. Department of Health and Human Services

Drugs

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Oral Sodium Phosphate (OSP) Actions Questions and Answers

1. What actions did the FDA take today?

As a result of new safety information, FDA is requiring the manufacturer of the prescription drugs Visicol and OsmoPrep to strengthen the product labeling to include a boxed warning, provide a Medication Guide for patients, and implement a risk evaluation and mitigation strategy (REMS) to ensure that the benefits of the products outweigh the risk of acute phosphate nephropathy, a type of acute kidney injury.  FDA is also requiring that a postmarketing clinical trial be conducted to further assess the risk of acute kidney injury with use of these products.

OSP products available in the OTC setting have the same risks as prescription products when used for bowel cleansing prior to colonoscopy or other procedures.  FDA plans to amend the labeling conditions for OSP products available in the OTC setting to address this concern with bowel cleansing use. 

Today, FDA is also responding to two citizen petitions regarding the use of OSP products for bowel cleansing. One petition, submitted by Natasha Leskovsek in September 2007 (Docket No. FDA-2007-P-0345), was granted, in part, because it requested a boxed warning for OSP products regarding the potential risks of certain kidney injuries. The other citizen petition, submitted on behalf of C.B. Fleet, Inc. in June 2003 (Docket No. FDA-1978-N-0021), requested FDA amend its regulation regarding the use of OSP products in the OTC setting for bowel cleansing, and it was denied.

2. What are OSP bowel cleansing products?

Bowel cleansing products are used to cleanse the stool out of your bowel before certain medical procedures, such as a colonoscopy.  The products work by causing you to lose fluid through your bowel movements.  This flushes out the bowel.  Two products, Visicol and OsmoPrep, are available by prescription only. There are several OSPs sold in the OTC setting, such as Fleet Phospho-soda labeled for use as a laxative. 

OSP OTC products when used for bowel cleansing have the same risks as the prescription products.  Physicians often direct patients to use higher doses of the OTC laxative products for bowel cleansing use.  The available data do not show a risk of acute kidney injury when these OTC products are used at laxative doses.

3. Who is at higher risk of acute phosphate nephropathy when using OSP bowel cleansing products?

You are at increased risk of developing acute phosphate nephropathy with the use of OSP bowel cleansing products if you:

  • are 55 years or older,
  • are dehydrated,
  • have a history of kidney problems,
  • have delayed bowel emptying,
  • have active colitis, or
  • take certain medications that affect kidney function, such as diuretic (fluid) pills, angiotensin converting enzyme (ACE) inhibitors (medications that lower blood pressure), angiotensin receptor blockers (ARBs, used to treat high blood pressure, heart or kidney failure), and possibly nonsteroidal anti-inflammatory drugs (NSAIDS, like ibuprofen or other arthritis medications).

4. What are the warning signs of acute phosphate nephropathy after using an oral sodium phosphate product?  

Acute phosphate nephropathy can result in a decrease in kidney function.  Symptoms can include malaise, lethargy, drowsiness, decreased amount of urine, and swelling of the 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 of developing this side effect.

5. What should I tell my healthcare professional?

Before you use OSPs for bowel cleansing, tell your healthcare professional if you:

  • Use a diuretic (fluid pill), ACE inhibitors, ARBs, or NSAIDs;
  • Have used a laxative for constipation in the past week; or
  • Have a history of kidney problems

6. What else should I know about OSP bowel cleansing products?

When using these products it is important to drink clear liquids.  Bowel cleansing products work by causing you to lose large amounts of fluid through your bowel movements.  Frequent, loose, and liquid bowel movements are expected.  It is very important that you replace this fluid to prevent dehydration.  Drinking large amounts of clear liquids helps you replace the fluid you lose and helps clean your bowel for your procedure.  Talk to your healthcare professional about what kinds of fluids you can drink to help lessen the chance of becoming dehydrated while using the OSP bowel cleansing products.

7. How soon can kidney problems occur after taking the OSP product? 

The kidney problems may occur within a few days or weeks after taking the OSP product.

8. Are there ways to reduce the risk of acute kidney injury?  

OSP bowel cleansing products should be used with caution by at-risk individuals, described above, if there is not another bowel cleansing option.  In addition, these OSP products for bowel cleansing should only be used under the supervision of a physician.  

9. Why is FDA now recommending new steps for the safe use of these products when they have been used for years?

The FDA has received adverse event reports of acute phosphate nephropathy associated with the use of OSP products. In 2006, FDA posted web information and a Science Paper describing reports of acute phosphate nephropathy associated with the use of prescription and over-the-counter OSP products.  More recently there have been new reports of acute phosphate nephropathy with use of these products.

10. Will OTC oral sodium phosphate products continue to be available on store shelves?

Yes, they will continue to be available over-the-counter as laxatives.  FDA plans to amend the labeling conditions for OSP products available in the OTC setting to address the concern with bowel cleansing use. Consumers should not use the OSP products available in the OTC setting for bowel cleansing use.

11. Over-the-counter OSP products are also used as laxatives.  Is this use safe? 

Yes.  To date the available data do not show a risk of acute kidney injury when these products are used at laxative doses, in accordance with the current labeling (up to 3 tablespoons per day).  Acute kidney injury has occurred only when the products have been used at higher doses.  Higher doses are for bowel cleansing and should not be used without a prescription from a healthcare provider.  FDA will continue to monitor and assess the safety of all laxative products containing OSP.

12. Are there other prescription or OTC products that can be used for bowel preparation prior to a medical procedure?

Yes, there are several prescription and OTC products available for bowel cleansing that do not contain sodium phosphates.  Before using any bowel cleansing product, it is recommended that you consult your healthcare provider to discuss which product is most appropriate.