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Overview: Sodium phenylbutyrate is used to manage urea cycle disorders (UCDs), which are genetic conditions where the body is unable to properly remove the waste products from protein digestion. It works by removing excess ammonia (a product of protein digestion) from the body. Common side effects include menstrual problems, loss of appetite, body odor, and changes in how things taste. Serious side effects include neurological problems, low potassium levels, and fluid retention. Sodium phenylbutyrate is available as oral tablets as well as pellets or powder that are mixed with liquid or food.

Uses

What is sodium phenylbutyrate used for?

Sodium phenylbutyrate is commonly used to manage urea cycle disorders (UCDs), which are genetic conditions where the body is unable to properly remove the waste products from protein digestion.

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

How does sodium phenylbutyrate work (mechanism of action)?

People with urea cycle disorders are unable to properly process nitrogen (a product of normal protein digestion), which can lead to toxic buildup of ammonia in your blood. Sodium phenylbutyrate binds to excess ammonia in the body and helps remove it from the body. 

How is sodium phenylbutyrate supplied (dosage forms)?

Brands and other names

  • Buphenyl
  • Olpruva
  • Pheburane

Dosage forms and strengths

  • 2 g, 3 g, 4 g, 5 g, 6 g, and 6.67 g packets of pellets for oral suspension
  • 250 g powder for oral suspension per bottle
  • 84 g of oral pellets per bottle
  • 500 mg oral tablets

How should I store sodium phenylbutyrate?

Oral Pellets (Pheburane) and Pellets for Oral Suspension (Olpruva). Sodium phenylbutyrate oral pellets (Pheburane) and pellets for oral suspension (Olpruva) should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Throw away any Pheburane pellets that remain 45 days after first opening the bottle.

Oral Tablet and Powder. Sodium phenylbutyrate oral tablet and powder should be stored at room temperature, between 59 F and 86 F (15 C and 30 C). Keep the bottle tightly closed after opening.

Side Effects

What are the most common side effects of sodium phenylbutyrate?

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

  • Menstrual problems
  • Loss of appetite
  • Body odor
  • Changes in how things taste

There may be other side effects of sodium phenylbutyrate 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 phenylbutyrate?

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

Severe Allergic Reactions. Sodium phenylbutyrate may cause allergic reactions, which can be serious. Stop taking sodium phenylbutyrate 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, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Brain or Central Nervous System (CNS) Effects. Sodium phenylbutyrate can affect your brain or central nervous system (CNS), especially at high doses. Talk to your health care provider if you have any of the following neurological symptoms.

  • Sleepiness
  • Tiredness
  • Lightheadedness
  • Headache
  • Changes in how things taste
  • Hearing loss
  • Disorientation
  • Memory problems
  • Worsening of existing nerve problems, such as nerve pain

Low Potassium Levels (Hypokalemia). Sodium phenylbutyrate can cause a low potassium level, which can be serious and may lead to death. Your health care provider may check your potassium levels, especially if you take certain other medicines. Keep all appointments to have your blood checked. Call your health care provider if you have any of the following symptoms of a low potassium level.

  • Weakness
  • Unusual tiredness
  • Muscle cramps or twitching
  • Constipation

Fluid Retention (Edema). Because sodium phenylbutyrate contains sodium, it can cause fluid retention, also called edema. Fluid retention can cause serious issues in people with certain conditions, such as heart failure or kidney problems. Call your health care provider right away if you have any of the following symptoms. 

  • Chest pain
  • Irregular heartbeat
  • Shortness of breath
  • Stretched or shiny skin
  • Swollen body parts, such as the belly or ankles

Warnings & Precautions

Who should not use sodium phenylbutyrate?

Allergies to Ingredients. People who are allergic to any of the following should not take sodium phenylbutyrate.

  • Buphenyl
  • Olpruva
  • Pheburane
  • Phenylbutyrate
  • Any of the ingredients in the specific product dispensed

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

Sudden Increase in Ammonia Levels (Oral Tablet and Powder). Sodium phenylbutyrate oral tablet and powder should not be taken if you are experiencing sudden, dangerous increase in blood ammonia levels (acute hyperammonemia). If you have symptoms such as nausea, vomiting, loss of appetite, confusion, or other sensory or behavioral problems, seek medical help right away.

What should I know about sodium phenylbutyrate before using it?

Do not take sodium phenylbutyrate unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share sodium phenylbutyrate with other people, even if they have the same condition as you. It may harm them.

Keep sodium phenylbutyrate out of the reach of children.

Carefully follow the instructions for use that come with the specific product you are taking.

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

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 determine if sodium phenylbutyrate is right for you.

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

Other Medicines and Supplements. Sodium phenylbutyrate may interact with other medicines and supplements. Before taking sodium phenylbutyrate, 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.

Diabetes or Problems Digesting Certain Types of Sugar (for Pheburane). Pheburane oral pellets contain a type of sugar called sucrose. Tell your health care provider if you have diabetes or any condition that causes problems absorbing or digesting certain types of sugar. These may include conditions such as hereditary fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase insufficiency.

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

  • Heart problems
  • Liver problems
  • Kidney problems
  • Fluid retention (edema)

Pregnancy. It is not known if or how sodium phenylbutyrate could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if sodium phenylbutyrate passes 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 take sodium phenylbutyrate while breastfeeding.

Interactions

Does sodium phenylbutyrate interact with foods or drinks?

Sodium phenylbutyrate should be taken with food.

It is unknown if drinking alcohol will affect sodium phenylbutyrate.

Does sodium phenylbutyrate 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 taking sodium phenylbutyrate.

  • A corticosteroid, such as dexamethasone, methylprednisolone, or prednisone, which is a medicine for certain inflammatory conditions
  • Divalproex sodium, valproate sodium (Depakote and others), and valproic acid, which are medicines used for seizures and other conditions
  • Haloperidol, which is an antipsychotic medicine for certain mental health conditions
  • Probenecid, which is a medicine commonly used for gout

This may not be a complete list of medicines that can interact with sodium phenylbutyrate. 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 phenylbutyrate?

If you or someone else has used too much sodium phenylbutyrate, 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 phenylbutyrate?

If you miss a dose, take it as soon as you remember that same day. If it is almost time for your next dose, skip the missed dose and only take the next dose. For Pheburane oral pellets, there should be at least three hours between two doses. Do not take double or extra doses.