Sodium Phosphate

Sodium Phosphate
Sodium Phosphate


Sodium phosphate is used in adults 18 years of age or older to empty the colon (large intestine, bowel) before a colonoscopy (examination of the inside of the colon to check for colon cancer and other abnormalities) so that the doctor will have a clear view of the walls of the colon. Sodium phosphate is in a class of medications called saline laxatives. It works by causing diarrhea so that the stool can be emptied from the colon.

Side Effects Of Sodium Phosphate

Sodium phosphate may cause side effects. Tell your doctor if either of these symptoms is severe or do not go away:

  • stomach pain
  • nausea
  • bloating

Some side effects can be serious. If you experience any of these symptoms or those listed in the WARNING section, call your doctor immediately:

  • irregular heartbeat
  • vomiting
  • fainting
  • seizures
  • rash
  • hives
  • itching
  • swelling of the eyes, face, lips, tongue, mouth or throat
  • burning or tingling of the lips, tongue, or mouth
  • throat tightness
  • difficulty breathing or swallowing

Sodium phosphate may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.

Warnings & Precautions

Before taking sodium phosphate:

  • tell your doctor and pharmacist if you are allergic to sodium phosphate, other medications, or any of the ingredients in the tablets. Check the prescription label or ask your pharmacist for a list of the ingredients.
  • tell your doctor if you have already taken sodium phosphate or used an enema containing sodium phosphate within the past 7 days. You should not take sodium phosphate more than once in 7 days.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention the medications listed in the IMPORTANT WARNING section and any of the following: alprazolam (Xanax), amiodarone (Cordarone, Pacerone); amitriptyline, desipramine (Norpramin), diazepam (Diastat, Valium), disopyramide (Norpace), dofetilide (Tikosyn), erythromycin (E.E.S., Erythrocin), estazolam, flurazepam, lorazepam (Ativan), medications for seizures, midazolam (Versed) moxifloxacin (Avelox), pimozide (Orap), quinidine (Quinidex, in Nuedexta), sotalol (Betapace, Betapace AF, Sorine), thioridazine, or triazolam (Halcion). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with sodium phosphate, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
  • if you are taking any other medications by mouth, talk to your doctor about when you should take them during your treatment with sodium phosphate. Medications that you take 1 hour before you take sodium phosphate may not be absorbed properly.
  • tell your doctor if you follow a low salt diet, if you had been drinking large amounts of alcohol or taking medications for anxiety or seizures and are now gradually decreasing your use of these substances, and if you have had heart surgery. Also tell your doctor if you have or have ever had a prolonged QT interval (a rare heart problem that may cause irregular heartbeat, fainting, or sudden death), an irregular heartbeat, a heart attack, chest pain, seizures, inflammatory bowel disease (IBD; a group of conditions in which all or part of the lining of the intestine is swollen, irritated, or has sores) difficulty swallowing.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding.

Dosage Of Sodium Phosphate

Sodium phosphate comes as a tablet to take by mouth. It is usually taken as one dose the night before a colonoscopy is scheduled and one dose the following morning (3 to 5 hours before the procedure). For each dose, your doctor will tell you to take a certain number of tablets with 8 ounces of clear liquid, wait 15 minutes, and then take more tablets with 8 ounces of clear liquid. You will repeat this several more times until you have taken all the tablets that your doctor prescribed for that dose.

It is very important that you drink the full amount of clear liquid with each dose of sodium phosphate, and that you drink plenty of clear liquid at other times before, during, and after your treatment with sodium phosphate. Examples of clear liquids are water, clear flavored broth, herbal or black tea, black coffee, flavored water, lemonade or limeade without pulp, apple or white grape juice, gelatin, popsicles, and clear soda (ginger ale). Do not drink alcohol, milk, or any liquids that are colored purple or red. Tell your doctor if you have trouble drinking clear liquids.


Do not let anyone else take your medication. Your prescription is probably not refillable, since you will not need more sodium phosphate after your colonoscopy.

Sodium phosphate has also been sold as a nonprescription laxative to relieve constipation. Many nonprescription oral sodium phosphate products are no longer sold in the United States, but some may still be available. If you are taking oral sodium phosphate for constipation, it is important that you take it exactly as directed on the package label. Do not take more of the medication than directed on the label for each dose, and do not take more than one dose in 24 hours even if you do not have a bowel movement after you take the medication. Do not give nonprescription oral sodium phosphate to a child 5 years of age or younger unless the child’s doctor tells you that you can. Taking too much nonprescription sodium phosphate may cause serious damage to the heart or kidneys or death.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.