
Prescription Drug Name:
Sodium Phenylbutyrate (SO-dee-um fen-ill-BYOU-tih-rate) Powder, Rx Only
ID:
f10bb4cd-8629-4a6e-97c7-54f7652f5779
Code:
34391-3
DESCRIPTION
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displayName: DESCRIPTION SECTION
FDA Article Code: 34089-3
CLINICAL PHARMACOLOGY
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displayName: CLINICAL PHARMACOLOGY SECTION
FDA Article Code: 34090-1
PHARMACOKINETICS
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displayName: PHARMACOKINETICS SECTION
FDA Article Code: 43682-4
The major sites for metabolism of sodium phenylbutyrate are the liver and kidney.
Significant gender differences were found in the pharmacokinetics of phenylbutyrate and phenylacetate, but not for phenylacetylglutamine. The pharmacokinetic parameters (AUC and Cmax), for both plasma phenylbutyrate and phenylacetate were about 30 to 50 percent greater in females than in males.
In patients who did not have urea cycle disorders but had impaired hepatic function, the metabolism and excretion of sodium phenylbutyrate were not affected. However, this information was obtained from unvalidated, uncontrolled case studies.
INDICATIONS AND USAGE
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displayName: INDICATIONS & USAGE SECTION
FDA Article Code: 34067-9
Sodium Phenylbutyrate Powder must be combined with dietary protein restriction and, in some cases, essential amino acid supplementation. (See
Previously, neonatal-onset disease was almost universally fatal within the first year of life, even when treated with peritoneal dialysis and essential amino acids or their nitrogen-free analogs. However, with hemodialysis, use of alternative waste nitrogen excretion pathways (sodium phenylbutyrate, sodium benzoate, and sodium phenylacetate), dietary protein restriction, and, in some cases, essential amino acid supplementation, the survival rate in newborns diagnosed after birth but within the first month of life is almost 80%. Most deaths have occurred during an episode of acute hyperammonemic encephalopathy. Patients with neonatal-onset disease have a high incidence of mental retardation. Those who had IQ tests administered had an incidence of mental retardation as follows: ornithine transcarbamylase deficiency, 100% (14/14 patients tested); argininosuccinic acid synthetase deficiency, 88% (15/17 patients tested); and carbamylphosphate synthetase deficiency, 57% (4/7 patients tested). Retardation was severe in the majority of the retarded patients.
In patients diagnosed during gestation and treated prior to any episode of hyperammonemic encephalopathy, survival is 100%, but even in these patients, most subsequently demonstrate cognitive impairment or other neurologic deficits.
In late-onset deficiency patients, including females heterozygous for ornithine transcarbamylase deficiency, who recover from hyperammonemic encephalopathy and are then treated chronically with sodium phenylbutyrate and dietary protein restriction, the survival rate is 98%. The two deaths in this group of patients occurred during episodes of hyperammonemic encephalopathy. However, compliance with the therapeutic regimen has not been adequately documented to allow evaluation of the potential for Sodium Phenylbutyrate Powder and dietary protein restriction to prevent mental deterioration and recurrence of hyperammonemic encephalopathy if carefully adhered to. The majority of these patients tested (30/46 or 65%) have IQ’s in the average to low average/borderline mentally retarded range. Reversal of pre-existing neurologic impairment is not likely to occur with treatment and neurologic deterioration may continue in some patients.
Even on therapy, acute hyperammonemic encephalopathy recurred in the majority of patients for whom the drug is indicated.
Sodium Phenylbutyrate Powder may be required life-long unless orthotopic liver transplantation is elected.
(See
CONTRAINDICATIONS
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displayName: CONTRAINDICATIONS SECTION
FDA Article Code: 34070-3
WARNINGS
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displayName: WARNINGS SECTION
FDA Article Code: 34071-1
Because Sodium Phenylbutyrate Powder is metabolized in the liver and kidney, and phenylacetylglutamine is primarily excreted by the kidney, use caution when administering the drug to patients with hepatic or renal insufficiency or inborn errors of beta oxidation. Probenecid is known to inhibit the renal transport of many organic compounds, including hippuric acid, and may affect renal excretion of the conjugated product of Sodium Phenylbutyrate Powder as well as its metabolite.
Use of corticosteroids may cause the breakdown of body protein and increase plasma ammonia levels.
PRECAUTIONS
id: 266a89dd-f8f1-436c-8cf1-3dc2aea6c192
displayName: PRECAUTIONS SECTION
FDA Article Code: 42232-9
Sodium Phenylbutyrate Powder should not be administered to patients with known hypersensitivity to sodium phenylbutyrate or any component of this preparation.
There have been published reports of hyperammonemia being induced by haloperidol and by valproic acid.
Sodium Phenylbutyrate Powder should be given to a pregnant woman only if clearly needed.
ADVERSE REACTIONS
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displayName: ADVERSE REACTIONS SECTION
FDA Article Code: 34084-4
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:
Renal: renal tubular acidosis
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.
The clinician is advised to routinely perform urinalysis, blood chemistry profiles, and hematologic tests.
OVERDOSAGE
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displayName: OVERDOSAGE SECTION
FDA Article Code: 34088-5
In the event of an overdose, discontinue the drug and institute supportive measures.
Hemodialysis or peritoneal dialysis may be beneficial.
DOSAGE AND ADMINISTRATION
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displayName: DOSAGE & ADMINISTRATION SECTION
FDA Article Code: 34068-7
The use of Sodium Phenylbutyrate Tablets is indicated for children weighing more than 20 kg and for adults.
The usual total daily dose of Sodium Phenylbutyrate Powder for patients with urea cycle disorders is 450 – 600 mg/kg/day in patients weighing less than 20 kg, or 9.9 – 13 g/m2/day in larger patients. The powder is to be taken in equally divided amounts with each meal or feeding (i.e., three to six times per day).
Sodium Phenylbutyrate Powder is indicated for oral use (via mouth, gastrostomy, or nasogastric tube) only. The powder is to be mixed with food (solid or liquid) for immediate use; however, when dissolved in water, Sodium Phenylbutyrate Powder has been shown to be stable for up to one week at room temperature or refrigerated. Sodium phenylbutyrate is very soluble in water (5 grams per 10 mL). When Sodium Phenylbutyrate Powder is added to a liquid, only sodium phenylbutyrate will dissolve, the excipients will not. The effect of food on sodium phenylbutyrate has not been determined.
Each level yellow teaspoon (enclosed) dispenses 3.2 grams of powder and 3 grams of sodium phenylbutyrate. Each level blue tablespoon (enclosed) dispenses 9.1 grams of powder and 8.6 grams of sodium phenylbutyrate.
Shake lightly before use.
The safety or efficacy of doses in excess of 20 grams per day has not been established.
NUTRITIONAL MANAGEMENT
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displayName: SPL UNCLASSIFIED SECTION
FDA Article Code: 42229-5
At the recommended dose of sodium phenylbutyrate, it is suggested that infants with neonatal-onset CPS and OTC deficiencies initially receive a daily dietary protein intake limited to approximately 1.6 g/kg/day for the first 4 months of life. If tolerated, the daily protein intake may be increased to 1.9 g/kg/day during this period. Protein tolerance will decrease as the growth rate decreases, requiring a reduction in dietary nitrogen intake. From 4 months to 1 year of age, it is recommended that the infant receive at least 1.4 g/kg/day, but 1.7 g/kg/day is advisable. From 1 to 3 years of age, the protein intake should not be less than 1.2 g/kg/day; 1.4 g/kg/day is advisable during this period. For neonatal-onset patients with carbamylphosphate synthetase deficiency or ornithine transcarbamylase deficiency who are at least 6 months of age, it is recommended that the daily protein intake be equally divided between natural protein and supplemental essential amino acids.
Patients with argininosuccinic acid synthetase deficiency and those with late-onset disease (partial deficiencies, including females heterozygous for ornithine transcarbamylase), initially may receive a diet containing the age-determined minimal daily natural protein allowance. The protein intake may be increased as tolerated and determined by plasma glutamine and other amino acid levels. However, many patients with partial deficiencies avoid dietary protein.
Citrulline supplementation is required and recommended for patients diagnosed with neonatal-onset deficiency of carbamylphosphate synthetase or ornithine transcarbamylase; citrulline daily intake is recommended at 0.17 g/kg/day or 3.8 g/m2/day.
The free-base form of arginine may be used instead of citrulline in patients with milder forms of carbamylphosphate synthetase and ornithine transcarbamylase deficiency (daily intake is recommended at 0.17 g/kg/day or 3.8 g/m2/day).
Arginine supplementation is needed for patients diagnosed with deficiency of argininosuccinic acid synthetase; arginine (free base) daily intake is recommended at 0.4 – 0.7 g/kg/day or 8.8 – 15.4 g/m2/day.
If caloric supplementation is indicated, a protein-free product is recommended. Caloric intake should be based upon the “Recommended Dietary Allowances”, 10th ed., Food and Nutrition Board, National Research Council, National Academy of Sciences, 1989.
HOW SUPPLIED
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displayName: HOW SUPPLIED SECTION
FDA Article Code: 34069-5
PATIENT PACKAGE INSERT
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displayName: SPL PATIENT PACKAGE INSERT SECTION
FDA Article Code: 42230-3
(SO-dee-um fen-ill-BYOU-tih-rate)
Sodium Phenylbutyrate Powder is prescribed along with changes in diet for long-term treatment of urea cycle disorders. Sodium Phenylbutyrate Powder can only be obtained with a prescription from your doctor.
Sodium Phenylbutyrate Powder must be taken exactly as the doctor prescribes; do not increase or decrease the dose of this medication without the doctor’s approval.
A patient or carrier of these disorders should wear a Medic Alert tag stating the diagnosis. In the event that the patient has a sudden, rapid accumulation of ammonia in the blood, and, therefore, in the brain, leading to unconsciousness, the doctor will be alerted to treat the disease properly.
Periodically, depending upon the severity of a particular patient’s urea cycle disorder, it will be necessary to perform blood tests. These include plasma ammonia, plasma amino acid levels, and other more routine blood tests to evaluate nutritional status.
Heart failure or decreased kidney function may lead to retention of the sodium content of Sodium Phenylbutyrate Powder with potentially serious consequences such as worsening heart failure, high blood pressure, and swelling. If these medical conditions are present, the doctor will determine if your child should take Sodium Phenylbutyrate Powder.
The dose of Sodium Phenylbutyrate Powder prescribed for adults and children is based upon the patient’s weight or size. It is very important that the full amount prescribed for any 24-hour period be taken. If a dose is missed it should be administered as soon as possible that same day. The total daily dose should be administered in equally divided amounts with meals.
What medications should I or my child avoid or be cautious of taking while on Sodium Phenylbutyrate Powder?
Patients with urea cycle disorders usually should not take Depakene® (valproic acid), a drug sometimes prescribed for seizure disorders, or Haldol® (haloperidol), a drug used to treat certain types of psychiatric or neurologic disorders. Both of these drugs have been reported to increase blood ammonia levels. Steroids may break down body protein, thereby increasing blood ammonia levels. The doctor should be consulted before administering medications containing steroids.
Probenecid, a medication used to treat gout, may affect the way the kidneys excrete Sodium Phenylbutyrate Powder (consult the doctor for details).
The most common side effect reported in premenopausal women taking Sodium Phenylbutyrate Powder was absent or irregular menstrual periods. Decreased appetite was reported in 4% of all people treated. Body odor and bad taste were each reported in 3% of all patients treated.
A breakdown product of Sodium Phenylbutyrate Powder has been associated mainly with sleepiness and light-headedness. Because these symptoms may also be due to the urea cycle going out of control, a doctor should see the patient immediately if these symptoms occur, so the cause can be determined. Blood tests should be performed periodically for adverse effects and for levels of medication and its breakdown products.
Sodium Phenylbutyrate Powder should be stored in a tightly closed bottle at room temperature.
PRINCIPAL DISPLAY PANEL- 250 Gram Bottle Carton
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displayName: PACKAGE LABEL.PRINCIPAL DISPLAY PANEL
FDA Article Code: 51945-4