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Sodium benzoate / sodium phenylacetate Side Effects

In Summary

Commonly reported side effects of sodium benzoate/sodium phenylacetate include: infection, respiratory tract disease, central nervous system disease, disorder of lymphatic system, hematologic disease, nutrition disorder, and vomiting. Other side effects include: cerebral edema, convulsions, metabolic acidosis, vascular disease, altered mental status, anemia, cardiac disorder, disorder of integument, fever, hyperammonemia, hyperglycemia, hypokalemia, hypotension, mental disorders, and renal disease. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to sodium benzoate / sodium phenylacetate: intravenous solution

As well as its needed effects, sodium benzoate / sodium phenylacetate may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking sodium benzoate / sodium phenylacetate, check with your doctor or nurse immediately:

More common:
  • Abdominal or stomach pain or cramps
  • blurred vision
  • decreased urine
  • dry mouth
  • fatigue
  • flushed, dry skin
  • fruit-like breath odor
  • increased hunger
  • increased thirst
  • increased urination
  • irregular heartbeat
  • loss of appetite
  • muscle pain or cramps
  • nausea or vomiting
  • numbness or tingling in the hands, feet, or lips
  • seizures
  • shortness of breath
  • sweating
  • troubled breathing
  • unexplained weight loss
  • unusual tiredness or weakness
Less common:
  • Agitation
  • anxiety
  • bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
  • bleeding or oozing from the puncture site, mouth, or nose that continues
  • bloody or cloudy urine
  • bloody, black, or tarry stools
  • confusion
  • coughing that sometimes produces a pink frothy sputum
  • depression
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • drowsiness
  • feeling, seeing, or hearing things that are not there
  • feeling that others are watching you or controlling your behavior
  • headache
  • lightheadedness
  • mood or mental changes
  • muscle tremors
  • nightmares or unusually vivid dreams
  • pale skin
  • rapid, deep breathing
  • restlessness
  • skin rash
  • sleepiness or unusual drowsiness
  • trouble with breathing when moving or walking
  • unusual bleeding or bruising

Minor Side Effects

Some sodium benzoate / sodium phenylacetate side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:
  • Diarrhea
  • fever

For Healthcare Professionals

Applies to sodium benzoate / sodium phenylacetate: intravenous solution


-The most frequently reported adverse reactions (incidence 6% or greater) are vomiting, hyperglycemia, hypokalemia, convulsions, and mental impairment.
-Patients 30 days of age or younger had more blood and lymphatic system disorders and vascular disorders (specifically hypotension), while patients older than 30 days had more GI disorders (specifically nausea, vomiting, and diarrhea).[Ref]

Nervous system

Very common (10% or more): Nervous system disorders (22%)
Common (1% to 10%): Convulsions, mental impairment, brain edema, coma
Frequency not reported: Brain death, brain herniation, subdural hematoma, areflexia, ataxia, brain infarction, brain hemorrhage, cerebral atrophy, clonus, depressed level of consciousness, encephalopathy, nerve paralysis, increased intracranial pressure, tremor[Ref]


Very common (10% or more): Metabolism and nutrition disorders (21%)
Common (1% to 10%): Hyperglycemia, hypokalemia, hyperammonemia, metabolic acidosis, hypocalcemia, acidosis
Frequency not reported: Blood carbon dioxide changes, blood glucose changes, increased blood pH, partial pressure of carbon dioxide changes, alkalosis, dehydration, fluid overload/retention, hypoglycemia, hyperkalemia, hypernatremia, alkalosis, tetany[Ref]


Very common (10% or more): Respiratory, thoracic, and mediastinal disorders (15%)
Common (1% to 10%): Respiratory distress
Frequency not reported: Increased respiratory rate, acute respiratory distress syndrome, dyspnea, hypercapnia, hyperventilation, Kussmaul respiration, pneumonia aspiration, pneumothorax, pulmonary hemorrhage, pulmonary edema, respiratory acidosis, respiratory alkalosis, respiratory arrest/failure[Ref]


Very common (10% or more): General disorders and administration-site conditions (14%), infections (12%), investigations (10%)
Common (1% to 10%): Injury, poisoning, and procedural complications; pyrexia; injection-site reaction
Frequency not reported: Asthenia, chest pain, multiorgan failure, edema, sepsis/septic shock, overdose[Ref]


Very common (10% or more): GI disorders (13%)
Common (1% to 10%): Vomiting, diarrhea, nausea
Frequency not reported: Abdominal distension, GI hemorrhage[Ref]


Very common (10% or more): Blood and lymphatic system disorders (11%)
Common (1% to 10%): Anemia, disseminated intravascular coagulation
Frequency not reported: Coagulopathy, pancytopenia, thrombocytopenia[Ref]


Common (1% to 10%): Cardiac disorders, vascular disorders, hypotension
Frequency not reported: Atrial rupture, bradycardia, cardiac or cardiopulmonary arrest/failure, cardiogenic shock, cardiomyopathy, pericardial effusion, decreased cardiac output, flushing, hemorrhage, hypertension, phlebothrombosis/thrombosis[Ref]


Common (1% to 10%): Skin and subcutaneous tissue disorders
Frequency not reported: Alopecia, blister, generalized pruritus, rash, urticaria[Ref]


Common (1% to 10%): Urinary tract infection
Frequency not reported: Anuria, urinary retention[Ref]


Common (1% to 10%): Psychiatric disorders, agitation
Frequency not reported: Acute psychosis, aggression, confusional state, hallucinations[Ref]


Common (1% to 10%): Renal and urinary disorders
Frequency not reported: Renal failure[Ref]


Frequency not reported: Cholestasis, hepatic artery stenosis, hepatic failure, hepatotoxicity, jaundice[Ref]


Frequency not reported: Blindness[Ref]


Frequency not reported: Acquired hemangioma[Ref]


1. "Product Information. Ammonul (sodium benzoate-sodium phenylacetate)." Ucyclyd Pharma, Scottsdale, AZ.

It is possible that some side effects of sodium benzoate / sodium phenylacetate may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.