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Generic name: sodium biphosphate and sodium phosphate (oral) [ SOE-dee-um-bye-FOS-fate-and-SOE-dee-um-FOS-fate ]
Drug class: Laxatives

Medically reviewed by Philip Thornton, DipPharm. Last updated on Oct 4, 2023.

What is OsmoPrep?

OsmoPrep tablets contain a combination of sodium biphosphate and sodium phosphate, both are forms of phosphorus, which is a naturally occurring substance that is important in every cell in the body.

OsmoPrep is used in adults to treat constipation and to clean the bowel before a colonoscopy. OsmoPrep cleans your colon by causing you to have diarrhea.

Using OsmoPrep to clean your colon helps your doctor see the inside of your colon more clearly during the colonoscopy.


You should not use OsmoPrep if you have kidney disease, a bowel obstruction, a perforated bowel, colitis or toxic megacolon, or a history of gastric bypass surgery or stomach stapling.

In rare cases, this medicine can cause kidney failure, especially if you have: kidney disease, congestive heart failure, severe constipation, inflammatory bowel disease, if you are over 55, or if you are dehydrated. Using certain other medicines can also increase your risk of kidney problems.

Do not use more than 1 dose in any 24-hour period. If you do not get any results within 30 minutes after using OsmoPrep, call your doctor before using another dose.

Using too much OsmoPrep can cause rare but life-threatening side effects on your kidneys and heart.

Before taking this medicine

You should not use OsmoPrep if you are allergic to sodium biphosphate and sodium phosphate, or if you have:

In rare cases, OsmoPrep can cause kidney failure, especially if:

Do not use Osmoprep if you have already used it within the past 7 days.

Ask a doctor or pharmacist if this medicine is safe to use if you have:

Ask a doctor before using OsmoPrep if you are pregnant or breast-feeding.

Do not give this medicine to a child without medical advice.

How should I take OsmoPrep?

Use OsmoPrep exactly as directed on the label, or as prescribed by your doctor.

Using too much OsmoPrep can cause rare but life-threatening side effects on your kidneys and heart.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

To keep from getting dehydrated, drink plenty of water or other clear liquid before, during, and after taking this medicine. Avoid milk, liquids that are colored red or purple, juice that contains pulp, or drinks that contain alcohol.

Carefully follow your doctor's dosing instructions about the timing of this medication and your procedure.

You may need to follow a special diet while treating constipation or preparing for your colonoscopy. Follow your doctor's instructions about any restrictions on food or beverages.

Store OsmoPrep at room temperature away from moisture and heat. Throw away any leftover medicine after your treatment ends.

What happens if I miss a dose?

Call your doctor for instructions if you miss a dose or do not finish all doses required before your colonoscopy.

Do not use more than the recommended dose of this medicine in any 24-hour period.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using OsmoPrep?

Do not use other laxatives or enemas.

OsmoPrep can make it harder for your body to absorb other medicines you take by mouth. Avoid taking oral medicines within 1 hour before or after you take this medicine.

OsmoPrep side effects

Get emergency medical help if you have signs of an allergic reaction to OsmoPrep: hives; dizziness; wheezing, difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using this medicine and call your doctor at once if you have:

Common OsmoPrep side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect OsmoPrep?

Ask a doctor or pharmacist before using OsmoPrep with any other medications, especially:

This list is not complete. Other drugs may interact with sodium biphosphate and sodium phosphate, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

More about OsmoPrep (sodium biphosphate / sodium phosphate)

Patient resources

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Fleet Phospho Soda, Visicol

Professional resources

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use OsmoPrep only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.