Glycerol phenylbutyrate

What Glycerol phenylbutyrate is used for

Quoted from the “Indications and Usage” section of the FDA-approved label.

RAVICTI is indicated for use as a nitrogen-binding agent for chronic management of patients with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. RAVICTI must be used with dietary protein restriction and, in some cases, dietary supplements (e.g., essential amino acids, arginine, citrulline, protein-free calorie supplements). Limitations of Use …

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. Read the full label on DailyMed →

Label quoted: the one for the most common form (liquid, oral), Ravicti, Horizon Therapeutics USA, Inc.; it covers 1 product in the FDA NDC Directory. The side effects, interactions, dosage and pregnancy quotes below come from this same label.

The FDA has 9 labels for products of this medicine (different makers and forms); uses can differ between them. Check the label that comes with your own medicine.

This page is not medical advice. Talk to your doctor or pharmacist before you start, stop or change any medicine.

Boxed warning

A boxed warning (“black box”) is the FDA’s strongest warning on a drug label, for serious or life-threatening risks.

The label quoted above has no boxed warning.

0 of 9 FDA labels for this medicine have a boxed warning.

Glycerol phenylbutyrate side effects

Quoted from the “Adverse Reactions” section of the FDA-approved label. Tell your doctor about any side effect that worries you.

The following clinically significant adverse reactions are described elsewhere in the labeling: Neurotoxicity [see Warnings and Precautions (5.1)] Pancreatic insufficiency or Intestinal Malabsorption [see Warnings and Precautions (5.2)] Most common adverse reactions (≥ 10%) in adults are: diarrhea, flatulence, and headache.

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(6.1) To report SUSPECTED ADVERSE REACTIONS, contact Amgen Inc. at 1-800-77-AMGEN (1-800-772-6436) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Assessment of adverse reactions was based on exposure of 45 adult patients (31 female and 14 male) with UCD subtype deficiencies of ornithine transcarbamylase (OTC, n = 40), carbamoyl phosphate synthetase (CPS, n = 2), and argininosuccinate synthetase (ASS, n = 1) in a randomized, double-blind, active-controlled (RAVICTI vs sodium phenylbutyrate), crossover, 4-week study (Study 1) that enrolled patients 18 years of age and older [see Clinical Studies (14.1)]. One of the 45 patients received only sodium phenylbutyrate prior to withdrawing on Day 1 of the study due to an adverse reaction. The most common adverse reactions (occurring in at least 10% of patients) reported during short-term treatment with RAVICTI were diarrhea, flatulence, and headache. Table 1 summarizes adverse reactions occurring in 2 or more patients treated with RAVICTI or sodium phenylbutyrate (incidence of at least 4% in either treatment arm). Table 1: Adverse Reactions Reported in 2 or More Adult Patients with UCDs (at least 4% in Either Treatment Arm) in Study 1 Number (%) of Patients in Study 1 Sodium Phenylbutyrate (N = 45) RAVICTI (N = 44) Diarrhea 3 (7) 7 (16) Headache 4 (9) 6 (14) Flatulence 1 (2) 6 (14) Abdominal pain 2 (4) 3 (7) Vomiting 2 (4) 3 (7) Decreased appetite 2 (4) 3 (7) Fatigue 1 (2) 3 (7) Dyspepsia 3 (7) 2 (5) Nausea 3 (7) 1 (2) Dizziness 4 (9) 0 Abdominal discomfort 3 (7) 0 Other Adverse Reactions RAVICTI has been evaluated in 77 patients with UCDs (51 adult and 26 pediatric patients ages 2 years to 17 years) in 2 open-label long-term studies, in which 69 patients completed 12 months of treatment with RAVICTI (median exposure = 51 weeks). During these studies there were no deaths. Adverse reactions reported in at least 10% of adult patients were nausea, vomiting, diarrhea, decreased appetite, dizziness, headache, and fatigue. Adverse reactions reported in at least 10% of pediatric patients ages 2 years to 17 years were upper abdominal pain, rash, nausea, vomiting, diarrhea, decreased appetite, and headache. RAVICTI has been evaluated in 17 patients with UCDs ages 2 months to less than 2 years in 3 open-label studies. The median exposure was 6 months (range: 0.2 to 20 months).

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. This is part of the section. Read the full label on DailyMed →

Glycerol phenylbutyrate drug interactions

Quoted from the “Drug Interactions” section of the FDA-approved label. Tell your pharmacist about every medicine, vitamin and herbal product you take.

Corticosteroids, valproic acid, or haloperidol: May increase plasma ammonia level; monitor ammonia levels closely. (7.1) Probenecid: May affect renal excretion of metabolites of RAVICTI, including phenylacetylglutamine (PAGN) and PAA. (7.2) CYP3A4 Substrates with narrow therapeutic index (e.g., alfentanil, quinidine, cyclosporine): RAVICTI may decrease exposure; monitor for decreased efficacy of the narrow therapeutic index drug.

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(7.3) Midazolam: Decreased exposure; monitor for suboptimal effect of midazolam. (7.3) 7.1 Potential for Other Drugs to Affect Ammonia Corticosteroids Use of corticosteroids may cause the breakdown of body protein and increase plasma ammonia levels. Monitor ammonia levels closely when corticosteroids and RAVICTI are used concomitantly. Valproic Acid and Haloperidol Hyperammonemia may be induced by haloperidol and by valproic acid. Monitor ammonia levels closely when use of valproic acid or haloperidol is necessary in patients with UCDs. 7.2 Potential for Other Drugs to Affect RAVICTI Probenecid Probenecid may inhibit the renal excretion of metabolites of RAVICTI including PAGN and PAA. 7.3 Potential for RAVICTI to Affect Other Drugs Drugs with Narrow Therapeutic Index That are Substrates of CYP3A4 RAVICTI is a weak inducer of CYP3A4 in humans. Concomitant use of RAVICTI may decrease the systemic exposure to drugs that are substrates of CYP3A4. Monitor for decreased efficacy of drugs with narrow therapeutic index (e.g., alfentanil, quinidine, cyclosporine) [see Clinical Pharmacology (12.3)]. Midazolam Concomitant use of RAVICTI decreased the systemic exposure of midazolam. Monitor for suboptimal effect of midazolam in patients who are being treated with RAVICTI.

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. Read the full label on DailyMed →

Glycerol phenylbutyrate dosage

Quoted from the “Dosage and Administration” section of the FDA-approved label. Your own dose is the one your doctor prescribes: do not change it on your own.

RAVICTI should be prescribed by a physician experienced in management of UCDs. For administration and preparation, see full prescribing information. (2.1, 2.6) Switching From Sodium Phenylbutyrate Tablets or Powder to RAVICTI: Patients should receive the dosage of RAVICTI that contains the same amount of phenylbutyric acid, see full prescribing information for conversion.

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(2.2) Initial Dosage in Phenylbutyrate-Naïve Patients (2.3): Recommended dosage range is 4.5 to 11.2 mL/m 2 /day (5 to 12.4 g/m 2 /day). For patients with some residual enzyme activity not adequately controlled with dietary restriction, the recommended starting dose is 4.5 mL/m 2 /day. Take into account patient's estimated urea synthetic capacity, dietary protein intake, and diet adherence. Dosage Adjustment and Monitoring: Follow plasma ammonia levels to determine the need for dosage titration. (2.4) Dosage Modifications in Patients with Hepatic Impairment: Start dosage at lower end of range. (2.5, 8.7) 2.1 Important Administration Instructions RAVICTI should be prescribed by a physician experienced in the management of UCDs. Instruct patients to take RAVICTI with food or formula and to administer directly into the mouth via oral syringe. Instruct patients to use the RAVICTI bottle and oral syringe as follows: Use a new reclosable bottle cap adapter with each new bottle that is opened. Open the RAVICTI bottle and twist on the new reclosable bottle cap adapter. Use a new and dry oral syringe to withdraw each prescribed dose of RAVICTI. Discard the oral syringe after each dose. Tightly close the tethered tab on the reclosable bottle cap adapter after each use. Do not rinse the reclosable bottle cap adapter. Discard bottle and any remaining contents 28 days after opening. If water or moisture enters the RAVICTI bottle, the contents will become cloudy in appearance. If the contents of the bottle appear cloudy at any time, do not use the remaining RAVICTI in the bottle and return it to the pharmacy to be discarded. Instruct that RAVICTI should be administered just prior to breastfeeding in infants who are breastfeeding. For patients who cannot swallow, see the instructions on administration of RAVICTI by nasogastric tube or gastrostomy tube [see Dosage and Administration (2.6)]. For patients who require a volume of less than 1 mL per dose via nasogastric or gastrostomy tube, the delivered dose may be less than anticipated. Closely monitor these patients using ammonia levels [see Dosage and Administration (2.6)]. The recommended dosages for patients switching from sodium phenylbutyrate to RAVICTI and patients naïve to phenylbutyric acid are different [see Dosage and Administration (2.2, 2.3)]. For both subpopulations: Patients 2 years of age and older: Give RAVICTI in 3 equally divided dosages, each rounded up to the nearest 0.5 mL Patients less than 2 years: Give RAVICTI in 3 or more equally divided dosages, each rounded up to the nearest 0.1 mL. The maximum total daily dosage is 17.5 mL (19 g).

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. This is part of the section. Read the full label on DailyMed →

Glycerol phenylbutyrate in pregnancy

Quoted from the pregnancy part of the FDA-approved label. Ask your doctor before you take any medicine while pregnant or planning a pregnancy.

Risk Summary Limited available data with RAVICTI use in pregnant women are insufficient to inform a drug-associated risk of major birth defects and miscarriage. In an animal reproduction study, administration of oral glycerol phenylbutyrate to pregnant rabbits during organogenesis at doses up to 2.7-times the dose of 6.87 mL/m 2 /day in adult patients resulted in maternal toxicity, but had no effects on embryo-fetal development.

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In addition, there were no adverse developmental effects with administration of oral glycerol phenylbutyrate to pregnant rats during organogenesis at 1.9 times the dose of 6.87 mL/m 2 /day in adult patients; however, maternal toxicity, reduced fetal weights, and variations in skeletal development were observed in pregnant rats administered oral glycerol phenylbutyrate during organogenesis at doses greater than or equal to 5.7 times the dose of 6.87 mL/m 2 /day in adult patients [see Data]. Report pregnancies to Amgen Inc. at 1-800-77-AMGEN (1-800-772-6436). The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Data Animal Data Oral administration of glycerol phenylbutyrate during the period of organogenesis up to 350 mg/kg/day in rabbits produced maternal toxicity, but no effects on embryo-fetal development. The dose of 350 mg/kg/day in rabbits is approximately 2.7 times the dose of 6.87 mL/m 2 /day in adult patients, based on combined area under the plasma concentration-time curve [AUCs] for PBA and PAA. In rats, at an oral dose of 300 mg/kg/day of glycerol phenylbutyrate (1.9 times the dose of 6.87 mL/m 2 /day in adult patients, based on combined AUCs for PBA and PAA) during the period of organogenesis, no effects on embryo-fetal development were observed. Doses of 650 mg/kg/day or greater produced maternal toxicity and adverse effects on embryo-fetal development including reduced fetal weights and cervical ribs at the 7 th cervical vertebra. The dose of 650 mg/kg/day in rats is approximately 5.7 times the dose of 6.87 mL/m 2 /day in adult patients, based on combined AUCs for PBA and PAA. No developmental abnormalities, effects on growth, or effects on learning and memory were observed through maturation of offspring following oral administration in pregnant rats with up to 900 mg/kg/day of glycerol phenylbutyrate (8.5 times the dose of 6.87 mL/m 2 /day in adult patients, based on combined AUCs for PBA and PAA) during organogenesis and lactation.

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. Read the full label on DailyMed →

When Glycerol phenylbutyrate should not be used

Quoted from the “Contraindications” section of the FDA-approved label.

RAVICTI is contraindicated in patients with known hypersensitivity to phenylbutyrate. Signs of hypersensitivity include wheezing, dyspnea, coughing, hypotension, flushing, nausea, and rash. Known hypersensitivity to phenylbutyrate. (4)

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. Read the full label on DailyMed →

Glycerol phenylbutyrate overdose

Quoted from the “Overdosage” section of the FDA-approved label. If someone may have taken too much, call Poison Help at 1-800-222-1222 (or 911 in an emergency).

While there is no experience with overdosage in human clinical trials, PAA, a toxic metabolite of RAVICTI, can accumulate in patients who receive an overdose [see Warnings and Precautions (5.1)]. If over-exposure occurs, call your Poison Control Center at 1-800-222-1222 for current information on the management of poisoning or overdosage.

— FDA label: Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025. Read the full label on DailyMed →

Forms and how it is given

Companies that list this medicine

Labelers in the FDA NDC Directory: the company named on the package (maker or distributor), with the number of prescription products.

• Novadoz Pharmaceuticals LLC1 product
• Lupin Pharmaceuticals, Inc.1 product
• Par Health USA, LLC1 product
• Zydus Pharmaceuticals USA Inc.1 product
• Horizon Therapeutics USA, Inc.1 product
• Camber Pharmaceuticals, Inc.1 product
• Aurobindo Pharma Limited1 product
• Navinta LLC1 product
• Teva Pharmaceuticals, Inc.1 product
• PAI Holdings, LLC dba PAI Pharma1 product

FDA approval history

• NDA: New Drug Application: how a new (usually brand-name) medicine is approved.
• ANDA: Abbreviated New Drug Application: how a generic version is approved.

Generic approvals (6)

• ANDA205742Ph Health · December 2, 2021
• ANDA218738Teva Pharms Inc · April 15, 2026
• ANDA219540Msn · April 15, 2026
• ANDA220313Aurobindo Pharma · April 15, 2026
• ANDA220568Navinta LLC · April 23, 2026
• ANDA220579Pai Holdings · July 28, 2026

Shortage status

To be discontinued · updated September 1, 2026 · first posted September 1, 2026

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Recalls

No recall linked to these products (by their NDC code) appears in the FDA enforcement reports.

Official identifiers

Next steps

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• RavictiBrand page: products, maker and price
• Novadoz Pharmaceuticals LLCMaker or distributor
• Lupin Pharmaceuticals, Inc.Maker or distributor
• Par Health USA, LLCMaker or distributor
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Sources

1. FDA-approved label on DailyMed (National Library of Medicine) — Ravicti, Horizon Therapeutics USA, Inc., effective October 29, 2025; via openFDA, FDA data exported October 30, 2026, retrieved October 31, 2026
2. NDC Directory (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 30, 2026, retrieved October 31, 2026
3. Drugs@FDA (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 30, 2026, retrieved October 31, 2026
4. Drug recall enforcement reports (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 27, 2026, retrieved October 31, 2026
5. Drug shortages (openFDA) — U.S. Food and Drug Administration (FDA), FDA data exported October 30, 2026, retrieved October 31, 2026

openFDA data is provided by the FDA as is; it may be incomplete. Always rely on the label that comes with your medicine. FDA Enforcement Report search →

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