Colonoscopy preparation is an important part of the colonoscopy procedure that is often done at home, following directions given by a gastroenterologist. The preparation is often the most uncomfortable part, because light sedation or "twilight sleep" is normally used during the procedure to prevent any discomfort. Many people will not even remember what happened during the actual test.

The goal of the colonoscopy prep is to eliminate all fecal matter (stool) from the colon so that the physician conducting the colonoscopy will have a clear view of the intestinal wall.

There are several ways to achieve this, and some doctors and patients will have their own unique methods that work best for them. There are, however, three main types of preparation: Golytely (also sold under the names Colyte, or Nulytely), phospho-soda, and sodium phosphate tablets (Osmo-Prep and Visicol).


This preparation will require a prescription from the doctor. It consists of a gallon jug with a powder mix inside. The patient will fill the jug with water and mix in the powder to make a drink. The instructions are usually to drink one 8 oz glass of the mixture every 10 minutes until the entire gallon is finished or eliminations are clear. After the first few glasses, bowel evacuation (in the form of diarrhea) will begin. Before the gallon is finished, many people find that their evacuations are totally clear and all the stool is cleaned out of the colon.

If eliminations do not become clear after the gallon is finished, an enema may be needed. Some people do experience nausea when drinking so much liquid, so the physician may prescribe an anti-nausea medication in case it is needed.
Golytely now comes in several flavors to make it more palatable and easier to drink.


Phospho-soda is a powder that is available over the counter either by itself or as part of a kit that also includes a laxative and an enema or suppository. The physician performing the colonoscopy will give instructions on which type of kit to purchase.
Three ounces of the phospho-soda liquid is mixed with water, or if the physician allows, other clear liquids such as ginger ale. After drinking the phospho-soda mixture, most patients are instructed to drink at least 3 glasses of another clear liquid. If part of a kit, the rest of the kit (laxative, enema, or suppository) will then be used according to doctor's instructions.

This preparation usually results in a bowel movement anywhere from 30 minutes to 6 hours after it is taken. Phospho-soda is also available in flavors to make it more palatable. Most physicians will instruct patients to call their office if the preparation does not progress as expected (for example, there is no bowel movement at all or the evacuations never becomes clear).

Sodium phosphate

Sodium phosphate tablets are prescribed by the doctor doing the colonoscopy. There are two different brands, depending on which your doctor prescribes -- Visicol, a 40-tablet regimen, and Osmo-Prep, a 32-tablet regimen.

With Visicol, 7 doses are taken in 15-minute intervals: 3 tablets are taken for 6 doses, and then 2 tablets are taken for 1 dose (20 tablets total). The next morning, 3 to 5 hours before the test, the same dosage is repeated (3 tablets for 6 doses, and then 2 tablets for 1 dose, in 15-minute intervals for a total of 20 tablets).

The prep begins to take effect about an hour after the first dosage of tablets is taken. A liquid diet is usually prescribed starting about 12 hours before starting the regimen. Potential side effects include bloating, nausea, vomiting, and abdominal pain.
In Osmo-Prep (the newer form), the tablets are taken the evening before and the morning of the colonoscopy. The evening before the test, 4 tablets are taken with 8 ounces of a clear liquid every 15 minutes for a total of 5 doses (20 tablets total). The next morning, about 3 to 5 hours before the test, another 3 doses of 4 tablets are taken at 15 minute intervals (12 tablets total).


To reduce any anal discomfort, use adult wet wipes or a water spray to clean the   rectal area instead of toilet paper.

Keep plenty of clear liquids on hand to drink. Water gets boring and staying hydrated is important.

Follow the doctor's instructions. You wouldn't want to have to do the prep all over again because you didn't get it right the first time.

Be prepared to spend most of the day before your test on the toilet.

Call the doctor's office for help if you have any trouble or don't understand the prep instructions.


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2010 Brookwood Medical Ctr Dr
Suite G - 100
Birmingham, AL 35209
Phone   205-877-1187
Fax       205-877-1150
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Alabama Digestive Health and Endoscopy Center