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Sodium benzoate / sodium phenylacetate Side Effects

Medically reviewed by Last updated on Jan 27, 2023.

Applies to sodium benzoate / sodium phenylacetate: intravenous solution. Other dosage forms:

Serious side effects

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

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

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

Other side effects

Some side effects of sodium benzoate / sodium phenylacetate 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:

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. 2005.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.