Glycerol Phenylbutyrate: uses, dosing, side effects & brands
Glycerol Phenylbutyrate is a medicine sold in the U.S. under 2 brand and generic names. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Available as
- Liquid
- Sold as
- 2 products — Glycerol Phenylbutyrate and Ravicti
- Prescription?
- Prescription only
- Generic available?
- Yes
How glycerol phenylbutyrate is dosed
From the FDA label for Glycerol Phenylbutyrate (application ANDA218738). Other glycerol phenylbutyrate products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Glycerol phenylbutyrate oral liquid 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 Glycerol Phenylbutyrate Oral Liquid: Patients should receive the dosage of glycerol phenylbutyrate oral liquid that contains the same amount of phenylbutyric acid, see full prescribing information for conversion. ( 2.2 ) Initial Dosage in Phenylbutyrate-Naïve Patie nts ( 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 Glycerol phenylbutyrate oral liquid should be prescribed by a physician experienced in the management of UCDs. Instruct patients to take glycerol phenylbutyrate oral liquid with food or formula and to administer directly into the mouth via oral syringe. Instruct patients…
Glycerol Phenylbutyrate side effects
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. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Teva at 1-888-838-2872 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 (glycerol phenylbutyrate oral liquid 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…
Who shouldn’t take glycerol phenylbutyrate
Glycerol phenylbutyrate oral liquid 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 )
Glycerol Phenylbutyrate drug interactions
Corticosteroids, valproic acid, or haloperidol : May increase plasma ammonia level; monitor ammonia levels closely. ( 7.1 ) Probenecid : May affect renal excretion of metabolites of glycerol phenylbutyrate oral liquid, including phenylacetylglutamine (PAGN) and PAA. ( 7.2 ) CYP3A4 Substrates with narrow therapeutic index (e.g., alfentanil, quinidine, cyclosporine) : Glycerol phenylbutyrate oral liquid may decrease exposure; monitor for decreased efficacy of the narrow therapeutic index drug. ( 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 glycerol phenylbutyrate oral liquid 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 Glycerol Phenylbutyrate Oral Liquid Probenecid Probenecid may inhibit the renal excretion of metabolites of glycerol phenylbutyrate oral liquid including PAGN and PAA. 7.3 Potential for Glycerol Phenylbutyrate Oral Liquid to Affect Other Drugs Drugs with narrow therapeutic index that are substrates of CYP3A4 Glycerol phenylbutyrate oral liquid is a weak inducer of CYP3A4 in humans. Concomitant use of glycerol phenylbutyrate oral liquid 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 glycerol phenylbutyrate oral liquid decreased the systemic exposure of midazolam. Monitor for suboptimal effect of midazolam in patients who are being treated with glycerol phenylbutyrate oral liquid.
Every glycerol phenylbutyrate product we track (2)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | 56/100 | Prescription | Liquid | No data | — | View → | |
| 2 | Not yet rated | Prescription | Liquid | No data | — | View → |
How long glycerol phenylbutyrate keeps
The date on a sealed pack is not the only one: some glycerol phenylbutyrate labels start a second clock once the product is opened or mixed, as short as 28 days.
Does glycerol phenylbutyrate expire? The in-use limits and storage rules from its labelsWhat people report to the FDA about glycerol phenylbutyrate
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 34 reports naming glycerol phenylbutyrate, and the FDA flagged 91% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- hyperammonaemic crisis7 reports
- hyperammonaemia5 reports
- vomiting5 reports
- ammonia increased4 reports
- nausea4 reports
- hyperammonaemic encephalopathy3 reports
- myelosuppression3 reports
- cough2 reports
Read these as a signal, not a rate. A report does not mean glycerol phenylbutyrate caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved July 25, 2026.
Related calculators
Frequently asked questions
What is glycerol phenylbutyrate?
Glycerol phenylbutyrate oral liquid is a clear, colorless to pale yellow oral liquid. It is insoluble in water and most organic solvents, and it is soluble in dimethylsulfoxide (DMSO) and greater than 65% acetonitrile. Glycerol phenylbutyrate is a nitrogen-binding agent.
Can you take glycerol phenylbutyrate with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run glycerol phenylbutyrate against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is glycerol phenylbutyrate sold under?
We track 2 glycerol phenylbutyrate-containing products in the U.S.: Glycerol Phenylbutyrate and Ravicti. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does glycerol phenylbutyrate come in?
Across the brands we track, glycerol phenylbutyrate is currently marketed as liquid, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic glycerol phenylbutyrate?
Yes. Our catalog lists 1 generic glycerol phenylbutyrate product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Glycerol Phenylbutyrate: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/glycerol-phenylbutyrate
- MLA
- “Glycerol Phenylbutyrate: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/glycerol-phenylbutyrate.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for glycerol phenylbutyrate on DailyMed (NIH) ↗.