Sodium phenylbutyrate Side Effects

Some side effects of sodium phenylbutyrate may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to sodium phenylbutyrate: oral powder for reconstitution, oral tablet

Even with treatment, urea cycle disorders can cause a build-up of ammonia in the blood which can result in life-threatening side effects. Seek emergency medical attention if you notice any signs of ammonia build-up, including mood or behavior changes, memory loss, thinking problems, muscle twitching, back and forth movement of the eyes, vomiting, increasing weakness, slurred speech, seizure (convulsions), and fainting.

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using sodium phenylbutyrate and call your doctor at once if you have any of these serious side effects:

Call your doctor at once if you have a serious side effect such as:

• fast, slow, or uneven heart rate;

• swelling, rapid weight gain;

• feeling like you might pass out; or

• changes in mood, personality, or behavior.

Less serious side effects of sodium phenylbutyrate may include:

• changes in menstrual periods;

• loss of appetite;

• headache;

• increased body odor;

• unusual or unpleasant taste in your mouth.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to sodium phenylbutyrate: oral powder for reconstitution, oral tablet

Hematologic

Frequency not reported: Aplastic anemia, ecchymoses

Cardiovascular

Frequency not reported: Arrhythmia, edema

Dermatologic

Frequency not reported: Rash

Gastrointestinal

Frequency not reported: Abdominal pain, gastritis, nausea and vomiting; constipation, rectal bleeding, peptic ulcer disease, pancreatitis

Genitourinary

Very common (10% or more): Amenorrhea/menstrual dysfunction (23%)

Metabolic

Common (1% to 10%): Decreased appetite (4%), body odor (3%), bad taste or taste aversion (3%)
Frequency not reported: Weight gain

Nervous system

Frequency not reported: Headache, syncope, neurotoxicity (manifested predominantly with somnolence, fatigue, and lightheadedness; and less frequently with headache, dysgeusia, hypoacusis, disorientation, impaired memory, and exacerbation of a pre-existing neuropathy)

Psychiatric

Frequency not reported: Depression

Renal

Frequency not reported: Renal tubular acidosis

Other

Laboratory Adverse Event in Patients with urea cycle disorders (UCDs):
Very common (10% or more): Acidosis (14%), hypoalbuminemia (11%)
Common (1% to 10%): Anemia (9%), alkalosis (7%), hyperchloremia (7%), hypophosphatemia (6%), increased alkaline phosphatase (6%), increased liver transaminases (4%), leukopenia (4%), leukocytosis (4%), decreased total protein (3%), thrombocytopenia (3%), hyperuricemia (2%), hyperphosphatemia (2%), hypernatremia (1%), hypokalemia (1%), hyperbilirubinemia (1%), thrombocytosis (1%)

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