Health Guide

Sodium benzoate and sodium phenylacetate (Oral route)


SOE-dee-um BEN-zoe-ate, SOE-dee-um fen-il-AS-e-tate

Brand Names:

  • Ucephan

Dosage Forms:

  • Solution



Hyperammonemia Agent

Uses of This Medicine:

Sodium benzoate and sodium phenylacetate combination is used to treat a condition caused by too much ammonia in the blood (hyperammonemia). This medicine works by causing less ammonia to be produced by the body.

Ammonia is formed from the breakdown of protein in the body. If the ammonia cannot be removed by the body, then a buildup may cause serious unwanted effects.

Sodium benzoate and sodium phenylacetate combination is available only with your doctor's prescription.

Before Using This Medicine:

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


This medicine has been tested in children and, in effective doses, has not been shown to cause different side effects or problems than it does in adults.

Older adults

Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing the use of sodium benzoate and sodium phenylacetate in the elderly with use in other age groups.

Other medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Other interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other medical problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Cancer Use of sodium benzoate and sodium phenylacetate may increase your chance of side effects
  • Edema (swelling) or
  • Heart disease Increased retention of water may make these conditions worse
  • Kidney disease or
  • Liver disease May increase the amount of medicine in your body

Proper Use of This Medicine:

It is important that you follow any special instructions from your doctor, such as following a low protein diet. If you have any questions about this, check with your doctor.


The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For injection dosage form (solution):
    • Treatment of too much ammonia in the blood:
      • Adults and children The dose is based on body weight and must be determined by the doctor.

Missed dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Precautions While Using This Medicine:

Your doctor should check your progress at regular visits to make sure that this medicine is working properly.

Side Effects of This Medicine:

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Stop taking this medicine and get emergency help immediately if any of the following effects occur:

More common
decreased urine
dry mouth
increase in frequency of seizures
increased thirst
irregular heartbeat
loss of appetite
mood changes
muscle pain or cramps
numbness or tingling in hands, feet, or lips
problems with movement, walking or speech
shortness of breath
swelling of face
unusual tiredness or weakness
yellow eyes or skin
Less common
Blood in stools
blood in urine
change in consciousness
coughing or vomiting blood
difficulty in breathing
loss of consciousness
mental changes
muscle cramps in hands, arms, feet, legs, or face
muscle tremors
persistent bleeding or oozing from puncture sites, mouth, or nose
rapid, deep breathing
shortness of breath
stomach cramps
tightness in chest
troubled breathing
Frequency unknown
Abnormally slow deep breathing
blue lips, fingernails, or skin
blurred vision
bulging soft spot on head of an infant
change in ability to see colors, especially blue or yellow
chest pain or discomfort
dizziness or fainting
injection site hemorrhage
irregular, fast or slow, or shallow breathing
severe headache
slow heartbeat
slow to respond
slurred speech
Symptoms of overdose
back pain
blue lips, fingernails, or skin
blurred vision
bulging soft spot on head of an infant
change in ability to see colors, especially blue or yellow
chest pain or discomfort
cold, clammy, pale skin
continuing nausea or vomiting
deep or fast breathing with dizziness
difficult or troubled breathing
dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
fast heartbeat
general feeling of discomfort or illness
high blood pressure
irregular, fast or slow, or shallow breathing
irregular heartbeats
loss of appetite
mood or mental changes
muscle twitching
no blood pressure
not alert
numbness to feet, hands and around mouth
rapid, shallow breathing
slow heart rate
stiff neck
swelling of face
swelling of feet or lower legs
thickening of bronchial secretions
trouble with coordination
unusual tiredness or weakness
yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
Changes in skin color
cold hands and feet
confusion or excitement
cough or hoarseness;
dry mouth;
fever or chills
flushed, dry skin;
fruit-like breath odor
increased hunger
increased thirst
increased urination
lower back or side pain
mental depression or anxiety
nightmares or unusually vivid dreams
painful or difficult urination
pain, redness, or swelling in arm or leg
skin disorders
unexplained weight loss
Less common
Bladder pain
bleeding, blistering, burning, coldness, discoloration of skin, feeling of pressure, hives, infection; inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at site
decrease in urine-concentrating ability
difficult, burning, or painful urination
frequent urge to urinate
pale skin
troubled breathing with exertion
trouble sleeping
unusual bleeding or bruising
Frequency unknown
full or bloated feeling or pressure in the stomach
itching skin
rash with flat lesions or small raised lesions on the skin
swelling of abdominal or stomach area
uncontrolled jerking movement

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

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

Last Updated: 6/12/2013
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