Home Drug Guide Sodium Phenylbutyrate

Drug Guide

Generic Name

Sodium Phenylbutyrate

Brand Names Buphenyl, Olpruva, Pheburane

Classification

Therapeutic: Ammonia scavenger in urea cycle disorders

Pharmacological: Oral nitrogen scavenging agent

FDA Approved Indications

Treatment of urea cycle disorders (UCDs) to manage hyperammonemia

Mechanism of Action

Sodium phenylbutyrate is metabolized to phenylacetate, which conjugates with glutamine to form phenylacetylglutamine, facilitating nitrogen excretion via the kidneys, thus reducing blood ammonia levels.

Dosage and Administration

Adult: Initial dose: 9-13 g/m²/day divided in 2-4 doses; adjust based on response and tolerability.

Pediatric: Dose is weight-based, typically starting at 250 mg/kg/day divided into multiple doses; adjust as needed.

Geriatric: No specific dosage adjustments; monitor closely due to potential decreased hepatic and renal function.

Renal Impairment: Use with caution; dose adjustments may be necessary based on renal function.

Hepatic Impairment: Use with caution; hepatic function should be monitored.

Pharmacokinetics

Absorption: Rapid absorption after oral administration.

Distribution: Widely distributed; crosses blood-brain barrier.

Metabolism: Metabolized in the liver to phenylacetate.

Excretion: Excreted primarily via the kidneys as phenylacetylglutamine.

Half Life: Approximately 1-2 hours for phenylacetate, but effective nitrogen scavenging lasts longer.

Contraindications

Hypersensitivity to sodium phenylbutyrate or any component of the formulation.

Precautions

Monitor for hypersensitivity reactions, hepatic and renal function, and blood ammonia levels. Use caution in patients with hepatic impairment, dehydration, or GI disturbances.

Adverse Reactions - Common

Nausea and vomiting (Common)
Headache (Common)
Diarrhea (Common)

Adverse Reactions - Serious

Hepatotoxicity (Uncommon)
Hypersensitivity reactions, including rash, anaphylaxis (Rare)
Electrolyte imbalances (Uncommon)

Drug-Drug Interactions

Valproic acid may increase ammonia levels; concurrent use warrants close monitoring.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor blood ammonia levels, liver function tests, electrolytes, and renal function.

Diagnoses:

Risk for ineffective airway clearance due to hyperammonemia
Risk for electrolyte imbalance

Implementation: Administer with meals or immediately after meals to reduce gastrointestinal upset. Ensure adequate hydration.

Evaluation: Assess for symptom improvement, normalizing ammonia levels, and absence of adverse effects.

Patient/Family Teaching

Take medication exactly as prescribed.
Discuss the importance of regular blood tests.
Report signs of hypersensitivity, hepatic or renal issues.
Maintain adequate hydration and diet.

Special Considerations

Black Box Warnings:

Use under strict medical supervision; risk of fatal hyperammonemia if improperly managed.

Genetic Factors: Genetic testing recommended for patients with suspected urea cycle disorders.

Lab Test Interference: May affect certain blood and urine tests; interpret results accordingly.

Overdose Management

Signs/Symptoms: Severe nausea, vomiting, diarrhea, somnolence, or altered mental status.

Treatment: Discontinue drug, provide supportive care, monitor vital signs, and consider hemodialysis in severe cases.

Storage and Handling

Storage: Store at room temperature, away from moisture and light.

Stability: Stable for the duration specified on the label when stored properly.