Sodium Phenylbutyrate (sodium phenylbutyrate)

Dosage of sodium phenylbutyrate is expressed in terms of the salt. Dosage of sodium phenylbutyrate is based on body weight in neonates, infants, and children weighing less than 20 kg and on body surface area in pediatric patients weighing at least 20 kg and in adults. Sodium phenylbutyrate tablets are used in pediatric patients weighing more than 20 kg and in adults. When the teaspoon provided by the manufacturer is used to measure sodium phenylbutyrate oral powder, each level teaspoonful of the powder provides 3 g of sodium phenylbutyrate. When the tablespoon provided by the manufacturer is used, each level tablespoonful of the powder provides 8.6 g of sodium phenylbutyrate.

For the chronic management of hyperammonemia in patients with urea cycle disorders, the usual oral dosage of sodium phenylbutyrate powder in neonates, infants and children weighing less than 20 kg is 450-600 mg/kg daily, given in 3-6 equally divided doses. In children weighing 20 kg or more and in adults, the usual oral dosage of sodium phenylbutyrate powder or tablets is 9.9-13 g/m2 daily, given in 3-6 equally divided doses. Safety and efficacy of dosages exceeding 20 g daily have not been established.

Sodium phenylbutyrate is administered orally. Sodium phenylbutyrate powder also may be administered via a gastrostomy or nasogastric tube. Although the effect of food on the drug has not been determined, sodium phenylbutyrate should be administered with meals or feedings. Sodium phenylbutyrate powder should be lightly shaken before use and then mixed with solid or liquid food before administration. Although sodium phenylbutyrate is very soluble in water and will dissolve when the powder is added to a liquid, the excipients in the commercially available formulation will not dissolve.

There is no enhanced messaging for this drug.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Hdac Inhibitors/Sodium Phenylbutyrate-Taurursodiol

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: The mechanism of the increased gastrointestinal (GI) adverse effects with concurrent sodium phenylbutyrate-taurursodiol (sodium phenylbutyrate-ursodoxicoltaurine) and other HDAC inhibitors is not known. Phenylbutyrate is a pan-histone deacetylase (HDAC) inhibitor.(1,2)

CLINICAL EFFECTS: Concurrent use of sodium phenylbutyrate-taurursodiol (sodium phenylbutyrate-ursodoxicoltaurine) and another HDAC inhibitor may result in GI adverse effects including nausea and vomiting.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer recommends avoiding use of other HDAC inhibitors in patients taking sodium phenylbutyrate-taurursodiol (sodium phenylbutyrate-ursodoxicoltaurine).(1) The CA manufacturer states sodium phenylbutyrate-taurursodiol should not be coadministered wiht other HDAC inhibitors.(2)

DISCUSSION: Concurrent use of sodium phenylbutyrate-taurursodiol (sodium phenylbutyrate-ursodoxicoltaurine) and another HDAC inhibitor may result in increased GI adverse effects.(1,2) HDAC inhibitors include: belinostat, panobinostat, phenylbutyrate, romidepsin, sodium butyrate, and valproic acid.

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Hdac Inhibitors/Vorinostat

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The mechanism of the increased thrombocytopenia and gastrointestinal bleeding with concurrent vorinostat and other HDAC inhibitors is not known.

CLINICAL EFFECTS: Concurrent use of vorinostat and another HDAC inhibitor may result in severe thrombocytopenia and gastrointestinal bleeding.

PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs).

PATIENT MANAGEMENT: The manufacturer recommends close monitoring of patients taking vorinostat with other HDAC inhibitors. The platelet count should be monitored every 2 weeks for the first 2 months.(1) If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling.

DISCUSSION: Concurrent use of vorinostat and another HDAC inhibitor may result in severe thrombocytopenia and gastrointestinal bleeding. The manufacturer recommends monitoring the platelet count every 2 weeks for the first 2 months.(1) HDAC inhibitors include: belinostat, panobinostat, phenylbutyrate, romidepsin, sodium butyrate, and valproic acid.

Myelosuppressives; Immunomodulators/Sodium Iodide I 131

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Sodium iodide I 131 can cause depression of the hematopoetic system. Myelosuppressives and immunomodulators also suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of sodium iodide I 131 with agents that cause bone marrow depression, including myelosuppressives or immunomodulators, may result in an enhanced risk of hematologic disorders, including anemia, blood dyscrasias, bone marrow depression, leukopenia, and thrombocytopenia. Bone marrow depression may increase the risk of serious infections and bleeding.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of sodium iodide I 131 states that concurrent use with bone marrow depressants may enhance the depression of the hematopoetic system caused by large doses of sodium iodide I 131.(1) Sodium iodide I 131 causes a dose-dependent bone marrow suppression, including neutropenia or thrombocytopenia, in the 3 to 5 weeks following administration. Patients may be at increased risk of infections or bleeding during this time. Monitor complete blood counts within one month of therapy. If results indicate leukopenia or thrombocytopenia, dosimetry should be used to determine a safe sodium iodide I 131 activity.(1)

DISCUSSION: Hematologic disorders including death have been reported with sodium iodide I 131. The most common hematologic disorders reported include anemia, blood dyscrasias, bone marrow depression, leukopenia, and thrombocytopenia.(1)

There are no moderate interactions for this drug.

Known hypersensitivity to sodium phenylbutyrate or any ingredient in the formulation. Treatment of acute hyperammonemia which is a medical emergency.

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

• Acute cognitive impairment
• Hypokalemia
• Kidney disease with reduction in glomerular filtration rate (GFr)
• Memory impairment

Adverse effects reported in 3% or more of patients receiving sodium phenylbutyrate include amenorrhea or menstrual dysfunction, decreased appetite, body odor, dysgeusia, acidosis, hypoalbuminemia, alkalosis and hyperchloremia, anemia, hypophosphatemia, increased concentrations of alkaline phosphatase and aminotransferase, leukopenia, leukocytosis, and thrombocytopenia.

More Frequent

• Hypoalbuminemia
• Hypophosphatemia
• Leukopenia
• Thrombocytopenic disorder

Less Frequent

• Alkalosis
• Anemia
• Hypernatremia
• Hyperuricemia
• Hypokalemia

Rare or Very Rare

• Cardiac arrhythmia
• Ecchymosis
• Edema
• Hyperchloremia
• Hyperphosphatemia
• Leukocytosis
• Rectal bleeding
• Renal tubular acidosis
• Thrombocytosis

More Frequent

• Amenorrhea
• Anorexia
• Body odor
• Dysgeusia
• Irregular menstrual periods

Less Frequent

• Acute abdominal pain
• Constipation
• Depression
• Gastritis
• Headache disorder
• Nausea
• Skin rash
• Syncope
• Vomiting
• Weight gain

Rare or Very Rare

• Aplastic anemia
• Peripheral sensory neuropathy

No enhanced messaging available.

Use of sodium phenylbutyrate tablets in neonates, infants and children weighing less than 20 kg is not recommended.

Category C. (See Users Guide)

Not known whether sodium phenylbutyrate is distributed into milk. Caution is advised if the drug is administered in nursing women.

No enhanced messaging available.