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Buphenyl Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 11/12/2015

Buphenyl (sodium phenylbutyrate) helps prevent a build-up of ammonia in the blood and is used to treat urea cycle disorders in people who lack certain liver enzymes needed to properly eliminate waste substances from the body. Buphenyl is available in generic form. Common side effects of Buphenyl include loss of appetite, increased body odor, unusual or unpleasant taste in your mouth, changes in menstrual periods (delayed/irregular/absent periods), headache.

The usual total daily dose of Buphenyl Tablets and Powder for patients with urea cycle disorders is 450-600 mg/kg/day in patients weighing less than 20 kg, or 9.9-13.0 g/m2/day in larger patients. Buphenyl may interact with valproic acid, haloperidol, probenecid, or steroids. Tell your doctor all medications and supplements you use. During pregnancy, Buphenyl should be used only when prescribed. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Our Buphenyl (sodium phenylbutyrate) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Buphenyl in Detail - Patient Information: Side Effects

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 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. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Buphenyl (Sodium Phenylbutyrate Tablets)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Buphenyl Overview - Patient Information: Side Effects

SIDE EFFECTS: Loss of appetite or menstrual changes (delayed/irregular/absent periods) may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: drowsiness/lightheadedness, easy bruising/bleeding, fast/pounding heartbeat, mental/mood changes, signs of infection (such as fever, persistent sore throat), tiredness, signs of metabolic imbalance (such as rapid breathing, muscle twitching/spasms).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

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

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Buphenyl (Sodium Phenylbutyrate Tablets)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Buphenyl FDA Prescribing Information: Side Effects
(Adverse Reactions)


The assessment of clinical adverse events came from 206 patients treated with sodium phenylbutyrate. Adverse events (both clinical and laboratory) were not collected systematically in these patients, but were obtained from patient-visit reports by the 65 co-investigators. Causality of adverse effects is sometimes difficult to determine in this patient population because they may result from either the underlying disease, the patient's restricted diet, intercurrent illness, or BUPHENYL. Furthermore, the rates may be under-estimated because they were reported primarily by parent or guardian and not the patient.

Clinical Adverse Events

In female patients, the most common clinical adverse event reported was amenorrhea/menstrual dysfunction (irregular menstrual cycles), which occurred in 23% of the menstruating patients.

Decreased appetite occurred in 4% of all patients. Body odor (probably caused by the metabolite, phenylacetate) and bad taste or taste aversion were each reported in 3% of patients.

Other adverse events reported in 2% or fewer patients were:

Gastrointestinal: abdominal pain, gastritis, nausea and vomiting; constipation, rectal bleeding, peptic ulcer disease, and pancreatitis each occurred in one patient.

Hematologic: aplastic anemia and ecchymoses each occurred in one patient.

Cardiovascular: arrhythmia and edema each occurred in one patient.

Renal: renal tubular acidosis

Psychiatric: depression

Skin: rash

Miscellaneous: headache, syncope, and weight gain

Neurotoxicity was reported in cancer patients receiving intravenous phenylacetate, 250-300 mg/kg/day for 14 days, repeated at 4-week intervals. Manifestations were predominately somnolence, fatigue, and lightheadedness; with less frequent headache, dysgeusia, hypoacusis, disorientation, impaired memory, and exacerbation of a pre-existing neuropathy. These adverse events were mainly mild in severity. The acute onset and reversibility when the phenylacetate infusion was discontinued suggest a drug effect.

Laboratory Adverse Events

In patients with urea cycle disorders, the frequency of laboratory adverse events by body system were:

Metabolic: acidosis (14%), alkalosis and hyperchloremia (each 7%), hypophosphatemia (6%), hyperuricemia and hyperphosphatemia (each 2%), and hypernatremia and hypokalemia (each 1%).

Nutritional: hypoalbuminemia (11%) and decreased total protein (3%).

Hepatic: increased alkaline phosphatase (6%), increased liver transaminases (4%), and hyperbilirubinemia (1%).

Hematologic: anemia (9%), leukopenia and leukocytosis (each 4%), thrombocytopenia (3%), and thrombocytosis (1%).

The clinician is advised to routinely perform urinalysis, blood chemistry profiles, and hematologic tests.

Read the entire FDA prescribing information for Buphenyl (Sodium Phenylbutyrate Tablets)

Buphenyl - User Reviews

Buphenyl User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Buphenyl sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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