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Sodium phosphates are used rectally to help with occasional constipation or to prepare for a rectal exam. Common side effects include nausea, stomach pain, feeling bloated, or anal discomfort. Serious side effects are less common but may include dehydration. To reduce your risk of dehydration, be sure to drink plenty of fluids while you are using this medicine. 

Uses

What are sodium phosphates used for?

Sodium phosphates are commonly used for the following.

  • To relieve occasional constipation
  • To prepare for certain procedures, such as a rectal exam

Sodium phosphates may also be used for other conditions as determined by your health care provider.

How do sodium phosphates work (mechanism of action)?

Sodium phosphates are a type of laxative known as an osmotic laxative or saline laxative. They pull water into your intestines. This helps to soften your poop and makes it easier to go to the bathroom.

How are sodium phosphates supplied (dosage forms)?

Brands and other names

  • Fleet
  • Fleet for Children

Pedia-Lax

Example dosage forms and strengths

  • 3.5 g dibasic sodium phosphate/9.5 g monobasic sodium phosphate rectal enema
  • 7 g dibasic sodium phosphate/19 g monobasic sodium phosphate rectal enema

How should I store sodium phosphates?

Storage requirements for sodium phosphates may vary by product. Most medicines should be kept in a cool, dry location that is out of reach of children and pets and not in direct sunlight. Ask your pharmacist if you are not sure how to store your product.

Side Effects

What are the most common side effects of sodium phosphates?

The most common side effects of sodium phosphates are listed below. Tell your health care provider if you have any of these side effects that bother you. 

  • Nausea
  • Stomach pain
  • Feeling bloated
  • Anal discomfort or stinging
  • Chills

There may be other side effects of sodium phosphates that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of sodium phosphates?

While less common, the most serious side effects of sodium phosphates are described below, along with what to do if they happen.

Severe Allergic Reactions. Sodium phosphates may cause allergic reactions, which can be serious. Stop using sodium phosphates and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Dehydration. Sodium phosphates may cause dehydration. To lower your risk of becoming dehydrated, you should drink plenty of fluids while you are using sodium phosphates. Dehydration may lead to problems such as low blood pressure, especially when you stand up (orthostatic hypotension), electrolyte problems, or kidney damage. Call your health care provider right away if you have any of the following symptoms of dehydration, low blood pressure, or kidney damage.

  • Dizziness or lightheadedness
  • Weakness or unusual tiredness
  • Confusion
  • Unsteadiness
  • Peeing less than normal
  • Swelling in your legs, ankles, and feet
  • Loss of appetite or nausea
  • A hard time catching your breath or chest pain or pressure
  • Seizures
  • Extreme thirst

Warnings & Precautions

Who should not use sodium phosphates?

Allergies to Ingredients. People who are allergic to any of the following should not use sodium phosphates.

  • Sodium phosphates
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific sodium phosphates products they stock.

What should I know about sodium phosphates before using them?

Sodium phosphates are available as a liquid that you insert in your rectum as an enema. This medicine is only for rectal use. Insert it gently into the rectum. Do not force it because this could cause an injury. Read and follow the directions that come with the medicine or use it as recommended by your health care provider. 

Sodium phosphates usually make you poop in 1-5 minutes after using them. Call your health care provider right away if no liquid comes out of the rectum 30 minutes after using it. 

Some products should only be used for a certain number of days unless recommended by your health care provider. Follow the instructions on the specific product you or your child are using. Do not use more than the recommended amount.

You should not use sodium phosphates more than once in a 24-hour period. This may cause harm or increase your risk of serious side effects. 

Keep sodium phosphates out of the reach of children.

Drink plenty of fluids while you are using this medicine. Dehydration is a possible side effect, and drinking fluids can help prevent this. See the Side Effects section for more details. 

You should stop using sodium phosphates and contact your health care provider if you have any of the following. These could be symptoms of a serious condition.

  • You do not poop after using it
  • You have rectal bleeding or pain
  • You get dehydrated (you may have symptoms such as peeing less often than usual, feeling thirsty, vomiting, or dizziness)

People who are 55 or older can be at greater risk of some side effects from sodium phosphates. Talk to your health care provider about your risks if you are in this age group.

What should I tell my health care provider before using sodium phosphates?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if sodium phosphates are right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have or have had any of the following.

Low-Sodium Diet. Tell your health care provider if you are following a low-salt or low-sodium diet before using sodium phosphates. This product contains sodium.

Other Medicines and Supplements. Sodium phosphates may interact with other medicines and supplements. Before using sodium phosphates, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how sodium phosphates could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should use sodium phosphates while you are pregnant or trying to get pregnant.

Breastfeeding. It is not known if sodium phosphates pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should use sodium phosphates while breastfeeding.

Interactions

Do sodium phosphates interact with foods or drinks?

Sodium phosphates contain sodium or salt. You should not use sodium phosphates if you are following a low-salt diet without talking to your health care provider. 

It is unknown if drinking alcohol will affect sodium phosphates.

Do sodium phosphates interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using sodium phosphates.

  • An angiotensin-converting enzyme (ACE) inhibitor, such as enalapril or lisinopril, which is a medicine for high blood pressure, heart failure, and certain kidney problems
  • An angiotensin II receptor blocker (ARB), such as losartan or valsartan, which is a medicine for high blood pressure, heart failure, and other heart conditions
  • Aspirin or a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen, naproxen, and others, which is in many prescription and OTC products for pain, swelling, and fever
  • Amiodarone, disopyramide (Norpace), dofetilide (Tikosyn), quinidine, or sotalol (Betapace), which are medicines used for an irregular heart rhythm
  • A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure
  • Lithium or thioridazine, which is a medicine used for certain mental health conditions
  • Moxifloxacin (Avelox), which is an antibiotic used to treat certain bacterial infections
  • Pimozide (Orap), which is a medicine used for Tourette syndrome
  • Any other laxative or enema

This may not be a complete list of medicines that can interact with sodium phosphates. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much sodium phosphates?

If you or someone else has used too much sodium phosphates, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of sodium phosphates?

Sodium phosphates are meant to be used only when needed. Use them according to the product labeling or as your health care provider recommends. Do not take double or extra doses.