sodium phenylbutyrate
Sodium phenylbutyrate is a medication that's used as part of a treatment plan for people with urea cycle disorders (UCDs). It helps prevent the buildup of ammonia in the blood. It comes in tablet and powder form, which are available as lower-cost generic medications. It also comes as oral pellet and oral suspension formulations that are only available as brand-name medications.
What is Sodium phenylbutyrate?
What is Sodium phenylbutyrate used for?
Long-term treatment for certain types of urea cycle disorders (UCDs)
How Sodium phenylbutyrate works
Sodium phenylbutyrate is a urea cycle disorder agent. It works by helping the body break down ammonia in people with urea cycle disorders (UCDs). This helps prevent a dangerous buildup of ammonia in the blood.
Normally, proteins in the liver turn ammonia into a waste product known as urea. The kidneys then get rid of urea by passing it in your urine. But in people with UCDs, the proteins that turn ammonia into urea either don't work correctly or are missing. This means that excess ammonia builds up, and the body can't get rid of it. Too much ammonia in the blood is very toxic, especially to the brain.
UCDs are caused by a genetic defect, and the symptoms of the condition start at birth. The toxic effects of ammonia are very serious for anyone, but especially for newborns. If not treated quickly, it can lead to seizures, coma, intellectual disabilities, and problems with motor skills.
Drug Facts
What are the side effects of Sodium phenylbutyrate?
Common Side Effects
- Changes in menstrual cycle (23%)
- Poor appetite (4%)
- Body odor (3%)
- Bad taste in the mouth (3%)
Other Side Effects
- Stomach pain or upset
- Nausea or vomiting
- Headache
- Fainting
- Weight gain
- Depression
- Rash
Source: DailyMed
The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Dizziness, loss of balance or coordination, confusion or trouble speaking
- Low potassium level—muscle pain or cramps, unusual weakness or fatigue, fast or irregular heartbeat, constipation
- Swelling of the ankles, hands, or feet
Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):
- Body odor
- Change in taste
- Irregular menstrual cycles or spotting
- Loss of appetite
Pros and cons of Sodium phenylbutyrate
Pros
Can help manage ammonia levels for people with UCDs
Comes in tablet, oral pellet, powder, and oral suspension form
Tablets and powder available as lower-cost generics
Powder can be given by mouth or through a feeding tube
Powder dissolved in water can be stored for up to 1 week
Cons
Must take several times a day
Missing a dose can be very serious if not taken in the same day.
Typically lifelong treatment, unless you get a liver transplant (if eligible)
Contains sodium, which can be dangerous for people with certain health conditions
Oral pellets contain sucrose, which can affect blood sugar levels.
Pharmacist tips for Sodium phenylbutyrate
While taking sodium phenylbutyrate, stick to a low-protein diet. When protein gets broken down by the body, it raises the amount of ammonia in the blood as a waste product. This can be dangerous if you have a UCD.
Depending on the type of UCD you have, you might need to take certain types of dietary supplements. You also might need to work with a nutrition expert to make sure you're getting the proper nutrition.
Your provider will do tests to check the level of sodium phenylbutyrate that's in your blood every so often. This is to make sure you're absorbing the right amount of the medication for your condition. Your provider will also do tests to make sure the ammonia and protein levels in your blood stay within the normal range.
It's recommended that you wear a Medic Alert tag (or some form of medical alert ID) if you have a UCD. This lets healthcare providers know you have this condition in case you need treatment in an emergency situation. An episode of high blood ammonia can cause you to pass out, which requires quick, emergency treatment.
For the sodium phenylbutyrate (Buphenyl) powder
Be sure to use the dosing spoons that are included with the medication to measure your dose properly. Household spoons should never be used to measure medications because they might not be accurate, even if you're specifically using a teaspoon or tablespoon.
Shake the sodium phenylbutyrate powder gently before measuring it out. The powder can be mixed with food, but must be eaten right away. If the food mixture sits for too long, the medication might not work as well. You can also mix the powder with water; you can store this mixture for up to 1 week at room temperature or in the refrigerator after it dissolves in the water.
For the Pheburane oral pellets
Use the included dosing spoon to measure Pheburane oral pellets to make sure you get an accurate dose. This dosing spoon measures out the dose in grams of sodium phenylbutyrate.
Swallow the oral pellets with a drink (e.g., water, fruit juices, protein-free infant formulas). You can also sprinkle the oral pellets onto a spoonful of applesauce or carrot puree, and then swallow the dose right away. Sprinkling it on other foods isn't recommended since it hasn't been studied.
Don't chew the oral pellets or mix them into liquids because this can damage the coating on the pellets. Also swallow the oral pellets right after drinking or sprinkling on top of applesauce or carrot puree so the coating doesn't dissolve. Damage to the coating might cause the medication to not work as well.
For the Olpruva oral suspension
When you get the medication, you'll get two different packets called Olpruva and Mix-Aid packets. The Olpruva packets contain sodium phenylbutyrate (the medication), and the Mix-Aid packets contain a substance that helps the medication become a mixture that you can drink when all added to water.
Pour all of the contents of the Mix-Aid packet into a cup with about 4 ounces (one-half cup) of water, and stir. Then, empty the entire Olpruva packet(s) needed for your dose into the cup, and stir to make a mixture.
Drink all of the mixture within 5 minutes of stirring. If you haven't consumed the mixture after 30 minutes, throw it away.
Add another 4 ounces (one-half cup) of water into the same cup. Then, drink the water to make sure you've taken all of the medication in the cup.
Frequently asked questions about Sodium phenylbutyrate
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What are the risks and warnings for Sodium phenylbutyrate?
Sodium phenylbutyrate can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
High sodium levels
Risk factors: Serious heart, liver, or kidney problems
The tablet, powder, oral pellets, and oral suspension forms of sodium phenylbutyrate all contain sodium. This can be dangerous for people who have serious kidney, liver, or heart problems. Too much sodium can build up in your blood, cause your body to hold onto water, and lead to swelling. This can cause high blood pressure and worsening medical problems. Talk to your provider before you take sodium phenylbutyrate if you have these conditions.
Damage to nerves
Sodium phenylbutyrate is broken down into a substance called phenylacetate. Some people receiving injections of phenylacetate (e.g., Ammunol (sodium phenylacetate / sodium benzoate)) have reported nerve damage. Sodium phenylbutyrate isn't approved as an injection, and studies show that nerve damage isn't likely to happen when taking sodium phenylbutyrate by mouth or through a feeding tube. While this risk is low, make sure to let your provider know if you experience extreme tiredness, dizziness, lightheadedness, headache, confusion, memory problems, or nerve pain.
Low potassium levels
It's possible that sodium phenylbutyrate could cause your potassium levels to drop too low. While quite rare, it's important to be aware of this risk. If you experience nausea or vomiting, muscle weakness or spasms, or irregular heart beat, let your provider know right away.
Contains sucrose (Pheburane oral pellets only)
Risk factors: History of diabetes | Genetic conditions affecting the ability to digest sugars
Pheburane oral pellets contain sucrose, which is a type of sugar. This can affect your blood sugar levels. If you have diabetes, talk to your provider before taking Pheburane to make sure it's safe for you. This medication should be avoided if you have certain conditions that affect your ability to digest sugars.
Sodium phenylbutyrate dosage forms
Typical dosing for Sodium phenylbutyrate
Your provider will determine the right total daily dose for you or your child. The total daily dose is split into equal doses throughout the day (3 to 6 times per day). Each dose is taken with each meal or feeding.
The powder can be taken by mouth or through a feeding tube. The tablets, oral pellets (Pheburane), and oral suspension (Olpruva) can only be taken by mouth.
Adults and children weighing more than 44 lbs (all formulations): The dose is based on your body surface area (BSA), which takes into account both your height and weight. The typical dose is 9.9 grams/m2 to 13 grams/m2 of BSA per day.
Children weighing less than 44 lbs (powder and oral pellets only): The dose is based on your child's body weight. The typical dose is 450 mg/kg to 600 mg/kg of body weight per day.
Sodium phenylbutyrate contraindications
Treating an emergency episode of high ammonia
What are alternatives to Sodium phenylbutyrate?
Long-term treatment for certain types of urea cycle disorders (UCDs)
Long-term treatment of urea cycle disorders (UCDs)
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References
Best studies we foundAcer Therapeutics Inc. (2022). Olpruva (sodium phenylbutyrate) for oral suspension [package insert].
American Chemical Society. (2021). Urea.
American Heart Association. (2022). Get the scoop on sodium and salt.
Centers for Disease Control and Prevention. (2020). Spoons are for soup, milliliters are for medicine.
Flint, B., et al. (2023). Body surface area. StatPearls.
Horizon Therapeutics plc. (n.d.). Urea cycle disorders 101.
Horizon Therapeutics USA, Inc. (2023). Bupheyl- sodium phenylbutyrate tablet; sodium phenylbutyrate powder [package insert]. DailyMed.
Medunik USA. (2023). Pheburane- sodium phenylbutyrate pellet; sodium phenylbutyrate kit [package insert]. DailyMed.
Mokhtarani, M., et al. (2013). Elevated phenylacetic acid levels do not correlate with adverse events in patients with urea cycle disorders or hepatic encephalopathy and can be predicted based on the plasma PAA to PAGN ratio. Molecular Genetics and Metabolism.
Stone, W. L., et al. (2023). Urea cycle disorders. StatPearls.
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