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Sodium phenylacetate/sodium benzoate (By injection)

Sodium Benzoate (SOE-dee-um BEN-zoe-ate), Sodium Phenylacetate (SOE-dee-um fen-il-AS-e-tate)

Lowers the amount of ammonia in your blood, and keeps the amount low. Too much ammonia damages your brain and nervous system. A problem called "urea cycle disorder" causes too much ammonia in the blood.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not receive this medicine if you have had an allergic reaction to sodium benzoate or sodium phenylacetate.

How to Use This Medicine:


  • Your doctor will prescribe your dose and schedule. This medicine is given through a needle placed in a vein.
  • A nurse or other health provider will give you this medicine.
  • You might also receive dialysis treatment with this medicine. This will help get the extra ammonia out of your blood faster.
  • You may also receive medicines to help prevent nausea and vomiting.
  • Carefully follow your doctor's instructions about any special diet. You might need to limit how much protein you eat.
  • Your doctor will give you or your child a few doses of this medicine until your condition improves, and then switch you to an oral medicine that works the same way. If you have any concerns about this, talk to your doctor.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are also using probenecid (Benemid®), valproic acid (Depakene®), medicine to treat an infection (such as amoxicillin, amoxicillin/clavulanate, penicillin, Amoxil®, Augmentin®, Trimox®, or Veetids®), or a steroid medicine (such as dexamethasone, prednisolone, prednisone, or Medrol®).

Warnings While Using This Medicine:

  • Make sure your doctor knows if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, congestive heart failure, edema (body swelling), low potassium in the blood, nervous system problems, or a history of seizures.
  • This medicine may cause unwanted effects on the nervous system. Check with your doctor right away if you or your child have lightheadedness, muscle tingling or weakness, sleepiness or unusual drowsiness, or tiredness.
  • Check with your doctor right away if you or your child have more than one of the following symptoms while receiving this medicine: confusion; deep or fast breathing with dizziness; muscle tremors; nausea; numbness of the feet, hands, and around the mouth; rapid, deep breathing; restlessness; stomach cramps; or unusual tiredness or weakness.
  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments. Blood tests may be needed to check for unwanted effects.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Burning, redness, swelling, or pain when the needle is placed.
  • Change in how much or how often you urinate, or painful urination.
  • Chest pain.
  • Confusion, headache, or trouble thinking clearly.
  • Dry mouth, increased thirst, muscle cramps, nausea, or vomiting.
  • Increased thirst or hunger.
  • Lightheadedness, dizziness, or fainting.
  • Numbness and tingling in your hands, feet, and around the mouth.
  • Seizures.
  • Shortness of breath or troubled breathing.
  • Unusual bleeding or bruising.
  • Unusual tiredness or weakness.

If you notice these less serious side effects, talk with your doctor:

  • Diarrhea.
  • Feeling anxious, nervous, or restless.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 5/1/2020

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