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Sodium benzoate / sodium phenylacetate Side Effects

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

For the Consumer

Applies to sodium benzoate / sodium phenylacetate: intravenous solution

Other dosage forms:

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

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 common side effects are vomiting, hyperglycemia, hypokalemia, convulsions, and mental impairment[Ref]


Very common (10% or more): Gastrointestinal disorders (13%)
Common (1% to 10%): Vomiting (9%), diarrhea (3%), nausea (3%)
Frequency not reported (less than 3%): Abdominal distension, gastrointestinal hemorrhage[Ref]


Common (1% to 10%): Hyperglycemia (7%), hypokalemia (7%), hyperammonemia (5%), metabolic acidosis (4%), acidosis (3%), hypocalcemia (3%)
Frequency not reported (less than 3%): Alkalosis, dehydration, fluid overload/retention, hypoglycemia, hyperkalemia, hypernatremia, alkalosis, tetany[Ref]

Nervous system

Very common (10% or more): Nervous system disorders (22%)
Common (1% to 10%): Mental impairment (6%), convulsions (6%), brain edema (5%), coma (3%),
Frequency not reported (less than 3%): Areflexia, ataxia, brain infarction, brain hemorrhage, cerebral atrophy, clonus, depressed level of consciousness, encephalopathy, nerve paralysis, intracranial pressure increased, subdural hematoma, tremor[Ref]


Very common (10% or more): Blood and lymphatic disorders (11%)
Common (1% to 10%): Anemia (4%), disseminated intravascular coagulation (3%)
Frequency not reported (less than 3%): Coagulopathy, pancytopenia, thrombocytopenia, hemorrhage, phlebothrombosis/thrombosis[Ref]


Very common (10% or more): Respiratory, thoracic and mediastinal disorders (15%)
Common (1% to 10%): Respiratory distress (3%)
Frequency not reported (less than 3%): Acute respiratory distress syndrome, dyspnea, hypercapnia, hyperventilation, Kussmaul respiration, pneumonia aspiration, pneumothorax, pulmonary hemorrhage, pulmonary edema, respiratory acidosis or alkalosis, respiratory arrest/failure[Ref]


Very common (10% or more): Psychiatric disorders (5%)
Common (1% to 10%): Agitation (3%)
Frequency not reported (less than 3%): Acute psychosis, aggression, confusional state, hallucinations[Ref]


Common (1% to 10%): Urinary disorders (4%), urinary tract infection (3%)[Ref]


Common (1% to 10%): Skin and subcutaneous tissue disorders (6%)
Frequency not reported (less than 3%): Alopecia, blister, generalized pruritus, rash, urticaria[Ref]


Frequency not reported (less than 3%): Cholestasis, hepatic artery stenosis, hepatic failure/hepatotoxicity, jaundice[Ref]


Very common (10% or more): General disorders and administration- site conditions (14%), infections (12%), injury, poisoning and procedural complications (12%)
Common (1% to 10%): Pyrexia (5%), injection -site reaction (3%)
Frequency not reported (less than 3%): Asthenia, brain death, chest pain, multiorgan failure, edema, sepsis/septic shock, brain herniation, subdural hematoma, overdose, blood carbon dioxide changes, blood glucose changes, blood pH increased, cardiac output decreased, pCO2 changes, respiratory rate increased[Ref]


Common (1% to 10%): Renal disorders (4%)
Frequency not reported (less than 3%): Anuria, renal failure, urinary retention[Ref]


Frequency not reported (less than 3%): Blindness[Ref]


Frequency not reported (less than 3%): Hemangioma acquired[Ref]


Common (1% to 10%): Cardiac disorders (9%), vascular disorders (6%), hypotension (4%)
Frequency not reported (less than 3%): Atrial rupture, bradycardia, cardiac or cardiopulmonary arrest/failure, cardiogenic shock, cardiomyopathy, pericardial effusion, flushing, hypertension[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.