Information about the Fleet Phospho-soda® bowel preparation
In order to undergo a colonoscopy for screening for colorectal cancer or for evaluation of
symptoms such as rectal bleeding or a change in bowel habit, it is important that the
bowel is thoroughly cleaned out. This is accomplished by not eating solid foods for a
period of time before the colonoscopy (usually one day) and by taking a bowel
preparation that acts to clean out the large bowel. The cleanliness of the colon in part
determines when a return colonoscopy will be needed.
The most commonly used bowel preparation in the United States is Phospho-soda® made
by the Fleet company. This product is based on the osmotic effect of phosphate, which
promotes accumulation of fluid in the bowel, which acts to clear out the bowel contents.
This preparation involves drinking one and a half ounces of Phospho-soda® with fluids
the day before the procedure and the other one and a half ounces taken with more fluids
up to three hours before the colonoscopy is performed. Because this type of preparation
can lead to dehydration it is essential that plenty of fluids are taken the day before and the
morning of the colonoscopy.
Other commonly used bowel preparations contain a nonabsorbable substance called
polyethylene glycol (PEG) which promote bulk movement through the colon. These
types of preparations such as GoLytely or Colyte require drinking a gallon of the clean-
out solution the day before the procedure. This preparation is safe but the inability to
consume the full amount in some patients, results in a less optimal bowel preparation.
Moreover, patients generally prefer the smaller volume of the Phospho-soda®
Due to a recently published study in the Journal of the American Society of Nephrology
there is concern that Phospho-soda® can lead to kidney problems. Dr. Markowitz and his
colleagues reported a series of patients in which a specific type of kidney problems was
noted. In some of the cases, patients had taken Phospho-soda® as a bowel preparation.
The authors concluded that the Phospho-soda® may have contributed to the kidney
problems. This study has received national attention since Phospho-soda® is so widely
used. However, the study has a number of drawbacks including the fact that it was not a
controlled study and one cannot really tell what caused the kidney problems in this small
group of patients. In some cases, the patients had health conditions for which they should
not have received this particular bowel preparation and it is not clear whether the patients
drank sufficient liquids, which the manufacturer clearly instructs. Some patients were
taking drugs on angiotensin converting enzyme (ACE)-I inhibitors, angiotensin receptor
blocking (ARB) and/or diuretic drugs. Moreover, other studies demonstrate that
Phospho-soda® is safe and does not cause any more problems with fluid imbalances than
the PEG based bowel preparations. About 5 million bowel-cleaning doses of Phospho-
soda® are sold each year in the USA with an adverse reaction rate of 10 per million doses
There are situations in which patients should not receive Phospho-soda® including
kidney failure (renal insufficiency), moderate to severe congestive heart failure, cirrhosis
and ascites, obstruction of the digestive tract and children under the age of five. Patients
with multiple illnesses such as hypertension for which they are taking more than one
medication, heart problems and other conditions such as diabetes should consult their
physician as to what bowel preparation is best. Patients who have multiple illnesses may
also not be good candidates for a screening colonoscopy since the risks may outweigh the
benefits of such testing. Caution should be exercised when using Phospho-soda® in
elderly or debilitated patients, those on ACE-1, ARB, diuretics and/or NSAIDs, and those
with cardiac disease or electrolyte disturbances.
For the average healthy patient or a patient with well-controlled hypertension, diabetes,
and other disorders who is undergoing colonoscopy, Phospho-soda® remains a safe and
very effective bowel preparation. Drinking lots of fluids the day before the test and the
morning of the procedure is key to ensuring an optimal preparation and preventing
dehydration that may be a factor in the very rare instances of complications. Phospho-
soda® should be taken according to manufacturer’s instructions. The two doses should be
administered between 6 and 12 hours apart. If there is any question which bowel
preparation is best for a given patient the physician ordering the test or the doctor who
will perform the test should be consulted.
This document has been prepared by the Dr. Sheila Crowe on behalf of the endoscopy
group at the University of Virginia after a review of the literature. Readers may also
want to read “Oral Sodium Phosphate Solutions for Bowel Preparation: Literature
Review and Recommendations of an Industry-Sponsored Advisory Panel Regarding Safe
and Effective Use” by D. K. Rex, et al. This report and additional information can be
obtained at www.phosphosoda.com.